Part I deals with foundry equipment, materials used, furnaces and

Transcriber’s Notes

Text printed in italics in the original work are represented between

underscores as in _text_. Small capitals have been transcribed as

ALL CAPITALS. ^{text} represents a superscript text, _{text}

respresents a subscript text.

More Transcriber’s Notes may be found at the end of this text.

INVENTORS AT WORK

[Illustration: Copyright by Park & Co., Brantford, Ontario.

PROFESSOR ALEXANDER GRAHAM BELL.]

Inventors at Work

With Chapters on Discovery

By George Iles

Author of “Flame, Electricity and the Camera”

Copiously Illustrated

[Illustration]

New York

Doubleday, Page & Company

1907

Copyright, 1906, by

GEORGE ILES

_Published October, 1906_

All rights reserved, including that of translation into foreign

languages, including the Scandinavian

TO MY FRIEND

JOSEPHUS NELSON LARNED

OF BUFFALO, NEW YORK

CONTENTS

PAGE

LIST OF ILLUSTRATIONS xiii

ACKNOWLEDGMENTS xxi

CHAPTER

I. INTRODUCTORY 1

II. FORM

Form as important as substance. Why a joist is stiffer than a

plank. The girder is developed from a joist. Railroad rails are

girders of great efficiency as designed and tested by Mr. P. H.

Dudley 5

III. FORM CONTINUED. BRIDGES

Roofs and small bridges may be built much alike. The queen-post

truss, adapted for bridges in the sixteenth century, neglected

for two hundred years and more. A truss replaces the Victoria

Tubular Bridge. Cantilever spans at Niagara and Quebec.

Suspension bridges at New York. The bowstring design is an arch

disguised. Why bridges are built with a slight upward curve. How

bridges are fastened together in America and in England 18

IV. FORM CONTINUED. LIGHTNESS, EASE IN MOTION

Why supports are made hollow. Advantages of the arch in

buildings, bridges and dams. Tubes in manifold new services.

Wheels more important than ever. Angles give way to curves 39

V. FORM CONTINUED. SHIPS

Ships have their resistances separately studied. This leads to

improvements of form either for speed or for carrying capacity.

Experiments with models in basins. The Viking ship, a thousand

years old, of admirable design. Clipper ships and modern

steamers. Judgment in design 52

VI. FORM CONTINUED. RESISTANCE LESSENED

Shapes to lessen resistance to motion. Shot formed to move

swiftly through the air. Railroad trains and automobiles of

somewhat similar shape. Toothed wheels, conveyors, propellers

and turbines all so curved as to move with utmost freedom 65

VII. FORM CONTINUED. ECONOMY OF LIGHT AND HEAT

Light economized by rightly-shaped glass. Heat saved by well-

designed conveyors and radiators. Why rough glass may be better

than smooth. Light is directed in useful paths by prisms. The

magic of total reflection is turned to account. Holophane Globes.

Prisms in binocular glasses. Lens grinding. Radiation of heat

promoted or prevented at will 72

VIII. FORM CONTINUED. TOOLS AND IMPLEMENTS

Tools and implements shaped for efficiency. Edge tools old and

new. Cutting a ring is easier than cutting away a whole circle.

Lathes, planers, shapers, and milling machines far out-speed the

hand. Abrasive wheels and presses supersede old methods. Use

creates beauty. Convenience in use. Ingenuity spurred by poverty

in resources 89

IX. FORM CONTINUED. ABORIGINAL ART

Form in aboriginal art, as affected by materials. Old forms

persist in new materials. Nature’s gifts first used as given,

then modified and copied. Rigid materials mean stiff patterns.

New materials have not yet had their full effect on modern

design 108

X. SIZE

Heavenly bodies large and small. The earth as sculptured a little

at a time. The farmer as a divider. Dust and its dangers. Models

may mislead. Big structures economical. Smallness of atoms.

Advantages thereof. Dust repelled by light 120

XI. PROPERTIES

Food nourishes. Weapons and tools are strong and lasting.

Clothing adorns and protects. Shelter must be durable.

Properties modified by art. High utility of the bamboo.

Basketry finds much to use. Aluminium, how produced and used.

Qualities long unwelcome or worthless are now gainful. Properties

created at need 135

XII. PROPERTIES CONTINUED

Producing more and better light from both gas and electricity.

The Drummond light. The Welsbach mantle. Many rivals of carbon

filaments and pencils. Flaming arcs. Tubes of mercury vapor 154

XIII. PROPERTIES CONTINUED

Steel: its new varieties are virtually new metals, strong, tough,

and heat resisting in degrees priceless to the arts. Minute

admixtures in other alloys are most potent 163

XIV. PROPERTIES CONTINUED

Glass of new and most useful qualities. Metals plastic under

pressure. Non-conductors of heat. Norwegian cooking box. Aladdin

oven. Matter seems to remember. Feeble influences become strong

in time 180

XV. PROPERTIES CONTINUED. RADIO-ACTIVITY

Properties most evident are studied first. Then those hidden from

cursory view. Radio-activity revealed by the electrician. A

property which may be universal, and of the highest import. Its

study brings us near to ultimate explanations. Faraday’s

prophetic views 197

XVI. MEASUREMENT

Methods beginning in rule-of-thumb proceed to the utmost

refinement. Standards old and new. The foot and cubit. The metric

system. Refined measurement as a means of discovery. The

interferometer measures 1/5,000,000 inch. A light-wave as an

unvarying unit of length 208

XVII. MEASUREMENT CONTINUED

Weight, Time, Heat, Light, Electricity, measured with new

precision. Exact measurement means interchangeable designs, and

points the way to utmost economies. The Bureau of Standards at

Washington. Measurement in expert planning and reform 219

XVIII. NATURE AS TEACHER

Forces take paths of least resistance. Accessibility decides

where cities shall arise. Plants display engineering principles

in structure. Lessons from the human heart, eyes, bones, muscles,

and nerves. What nature has done, art may imitate,--in the

separation of oxygen from air, in flight, in producing light, in

converting heat into work: Lessons from lower animals. A hammer-

using wasp 245

XIX. QUALIFICATIONS OF INVENTORS AND DISCOVERERS

Knowledge as sought by disinterested inquirers. A plenteous

harvest with few reapers. Germany leads in original research. The

Carnegie Institution at Washington 267

XX. OBSERVATION

What to look for. The eye may not see what it does not expect to

see. Lenses reveal worlds great and small otherwise unseen.

Observers of the heavens and of seashore life. Collections aid

discovery. Happy accidents applied to profit. Popular beliefs may

be based on truth. An engineer taught by a bank swallow 279

XXI. EXPERIMENT

Newton, Watt, Ericsson, Rowland, as boys were constructive. The

passion for making new things. Aid from imagination and trained

dexterity. Edison tells how the phonograph was born. Telephonic

messages recorded. Handwriting transmitted by electricity. How

machines imitate hands. Originality in attack 299

XXII. AUTOMATICITY AND INITIATION

Self-acting devices abridge labor. Trigger effects in the

laboratory, the studio and the workshop. Automatic telephones.

Equilibrium of the atmosphere may be easily upset 329

XXIII. SIMPLIFICATION

Simplicity always desirable, except when it costs too dear.

Taking direct instead of roundabout paths. Omissions may be

gainful. Classification and signaling simpler than ever before 340

XXIV. THEORIES HOW REACHED AND USED

Educated guessing. Weaving power. Imagination indispensable. The

proving process. Theory gainfully directs both observation and

experiment. Tyndall’s views. Discursiveness of Thomas Young 355

XXV. THEORIZING CONTINUED

Analogies have value. Many principles may be reversed with

profit. The contrary of an old method may be gainful. Judgment

gives place to measurement, and then passes to new fields 366

XXVI. NEWTON, FARADAY AND BELL AT WORK

Newton, the supreme generalizer. Faraday, the master of

experiment. Bell, the inventor of the telephone, transmits speech

by a beam of light 387

XXVII. BESSEMER, CREATOR OF CHEAP STEEL. NOBEL, INVENTOR OF NEW

EXPLOSIVES

Bessemer a man of golden ignorances. His boldness and

versatility. The story of his steel process told by himself.

Nobel’s heroic courage in failure and adversity. His triumph at

last. Turns an accidental hint to great profit. Inventors to-day

organized for attacks of new breadth and audacity 401

XXVIII. COMPRESSED AIR

An aid to the miner, quarryman and sculptor. An actuator for

pumps. Engraves glass and cleans castings. Dust and dirt removed

by air exhaustion. Westinghouse air-brakes and signals 417

XXIX. CONCRETE AND ITS REINFORCEMENT

Pouring and ramming are easier and cheaper than cutting and

carving. Concrete for dwellings ensures comfort and safety from

fire. Strengthened with steel it builds warehouses, factories and

bridges of new excellence 429

XXX. MOTIVE POWERS PRODUCED WITH NEW ECONOMY

Improvements in steam practice. Mechanical draft. Automatic

stokers. Better boilers. Superheaters. Economical condensers.

Steam turbines on land and sea 446

XXXI. MOTIVE POWERS, CONTINUED. HEATING SERVICES

Producer gas. Mond gas. Gas engines. Steam and gas engines

compared. Diesel engine best heat motor of all. Gasoline motors.

Alcohol engines. Steam and gas motors united. Heat and power

production together. District steam heating. Isolated plants.

Electric traction. Gas for a service of heat, light and power 457

XXXII. A FEW SOCIAL ASPECTS OF INVENTION

Why cities gain at the expense of the country. The factory

system. Small shops multiplied. Subdivided labor has passed due

bounds and is being modified. Tendencies against centralization

and monopoly. Dwellings united for new services. Self-contained

houses warmed from a center. The literature of invention and

discovery as purveyed in public libraries 478

INDEX 489

LIST OF ILLUSTRATIONS

PROFESSOR ALEXANDER GRAHAM BELL _Frontispiece_

BELL HOMESTEAD, BRANTFORD, ONTARIO _facing_ 2

Lens of ice focussing a sunbeam 5

Rubber strip suspended plank-wise and joist-wise 7

Board doubled breadthwise and edgewise 7

Telegraph poles under compression. Wires under tension 8

Rubber cylinder, flattened by compression, lengthened by tension 9

Rubber joist compressed along top, extended along bottom 10

Girder cut from joist 10

Rubber I-beam suspended flatwise and edgewise 10

Girder contours simple, built up, in locomotive draw-bars 11

Steel ore car 12

Bulb angle column, New York Subway 12

Strap rail and stringer, Mohawk & Hudson R. R., 1830 13

PLIMMON H. DUDLEY _facing_ 14

Dudley rails 16

Steel cross-ties and rails 17

King-post truss 18

Frames of four sides 19

Cross-section Arctic ship “Roosevelt” 20

Pair of compasses stretch a rubber strip 20

Queen-post truss 21

Upper part of roof truss, Interborough Power House, New York 21

Two queen-post trusses from a bridge 22

Palladio trusses 22

Burr Bridge, Waterford, N. Y. 23

Howe and Pratt trusses 24

Baltimore truss 25

Whipple Bridge 25

Simple cantilevers 26

Victoria Bridge, Montreal, original form 27

Victoria Bridge, Montreal, present form 28

Cantilever Bridge, near Quebec 29

Kentucky River Cantilever Bridge 30

Arch Bridge, Niagara Falls 31

Bowstring Bridge, Philadelphia 32

Williamsburg Bridge, New York City 33

Continuous Girder Bridge, Lachine, near Montreal 34

Rubber strip supported at 4 points, and at 2 points 34

Plate girder bridge 35

Lattice girder bridge, showing rivets 36

Bookshelf laden and unladen, showing camber 36

Pin connecting parts of bridge 37

Bridge rollers in section and in plan 38

Girder sections in various forms 39

Rubber cylinders solid and hollow compared in sag 40

Handle bar of bicycle in steel tubing 40

A sulky in steel tubing 41

Pneumatic hammer in steel tubing 41

Fishing rod in steel tubing 41

Bridge of steel pipe 41

Arch bridge of steel pipe 42

Spiral fire-lighter 42

Spiral weld steel tube 42

Largest stone arch in the world, Plauen, Germany 43

Church of St. Remy, Rheims, France 43

Curve of suspended chain 44

Dam across Bear Valley, California 44

Ferguson locking-bar 45

Hand-hole plates, Erie City water-tube boiler 46

Bullock cart with solid wheels 47

Ball thrust collar bearings 48

Rigid bearings for axles of automobiles 48

Hyatt helical roller bearing. Ditto supporting an axle 49

Treads and risers of stairs joined by curves 49

Corner Madison Square Garden, New York 50

Two pipes with funnel-shaped junction 50

MODEL BASIN, U. S. NAVY, WASHINGTON, D. C. _facing_ 54

Viking Ship 56

Clipper ship “Young America” 58

Steamship Kaiser Wilhelm II 60

Cargo steamer 61

U. S. Torpedo-boat destroyer 62

Cross-sections of ships 63

Racing automobile. Wedge front and spokeless wheels 66

Bilgram skew gearing 67

Grain elevator 68

Robins conveying belt 68

Ewart detachable link belting 69

Curves of turbines 70

Steel vanes of windmill 70

Pelton water wheel and jet 71

Luxfer prism 74

Fresnel lens 74

Lamp and reflector a unit 75

Inverted arc-light 75

Sacramento perch totally reflected in aquarium 77

Diagram illustrating total reflection 78

Holophane globe, sections 79

Holophane globe, diffusing curves 80

Holophane globe, three varieties 80

Holophane globe, and Welsbach mantle 81

Wire shortened while original direction is resumed 81

Four mirrors reflect a ray in a line parallel to first path 82

Prisms for Zeiss binocular glasses 82

Sections for Zeiss binocular glasses 83

Tools for producing optical surfaces 84

Bi-focal lens for spectacles 85

Canadian box-stove 86

Canadian dumb-stove 86

Tubing for radiator 87

Gold’s electric heater 87

Stolp wired tube for automobiles 87

Corrugated boiler 88

Pipe allowing contraction or expansion 88

Carving chisels and gouges 90

Lathe cutters 90

Ratchet bit brace 90

Eskimo skin scraper 91

Double tool drill cutting boiler plate 91

Common drill compared with ring drill 92

Twist drill 93

How a tool cuts metal 94

Dacotah fire-drill 94

Lathe, with parts in detail 95

Compound slide rest 96

Blanchard lathe 96

Turret lathe, with side and top views 97

Ericsson’s Monitor 98

Iron planer 99

Iron shaper 99

Milling machine 100

Milling cutters with inserted teeth 100

Milling cutters executing curves 101

Emery wheels 102

Carborundum wheel edges 102

Rolls to reduce steel in thickness 104

Gourd-shaded vessel, Arkansas 108

Gourd and derived pottery forms 109

Pomo basket 109

Bilhoola basket 110

Bilhoola basket, a square inch of 111

A free-hand scroll: same as woven 111

Yokut basket bowl 112

Sampler on cardboard 115

Bark vessel and derived form in clay 115

Vase from tumulus, St. George, Utah 116

Wooden tray. Clay derivative 116

Shell vessel. Earthen derivative 116

Electric lamps in candle shapes 117

Notre Dame de Bonsecours, Montreal 118

NEW AMSTERDAM THEATER, NEW YORK _facing_ 118

Cinders large and small on hearth 120

Cube subdivided into 8 cubes 121

Cube built of 27 cubes 122

Two rubber strips, varying as one and three in dimensions,

compared in sag 127

Air bubbles rising in oil 128

Dvorak sound-mill 132

Beam of light deflects dust 133

DR. CARL FREIHERR AUER VON WELSBACH _facing_ 156

Boivin burner for alcohol 157

Alcohol lamp with ventilating hood 158

Welsbach mantle 159

Tantalum lamp 160

Tungsten lamp of Dr Kuzel 160

Hewitt mercury-vapor lamp 161

SECTIONS PEARLITE AND STEEL _facing_ 164

CLEANING CARS BY THE “VACUUM” METHOD _facing_ 164

Open hearth furnace 165

PROFESSOR ERNST ABBE _facing_ 182

Bliss forming die 184

Bliss process of shell making 184

Mandolin pressed in aluminium 185

Pressed seamless pitcher 185

Barrel of pressed steel 185

Range front of pressed steel 186

Pressed paint tube and cover 186

Norwegian cooker 189

Aladdin oven 190

Mayer’s floating magnets 193

Alum crystal, broken and restored 194

Marble before and after deformation by pressure 195

PROFESSOR ERNEST RUTHERFORD _facing_ 202

PROFESSOR A. A. MICHELSON _facing_ 214

Michelson interferometer 215

Light-wave distorted by heated air 216

Ancient Egyptian balance 219

Rueprecht balance 220

Earnshaw compensated balance wheel 223

Riefler clock 224

Photometer 227

Compass needle deflected by electric wire 230

Compass needle deflected by electric coil 231

Maxwell galvanometer 231

Weston voltmeter 232

Micrometer caliper measuring 1/1000 inch 236

Plug and ring for standard measurements 237

Two lenses as pressed together by Newton 237

Newton’s rings 238

Flat jig or guide 239

Deciduous cypress 247

Deciduous cypress, hypothetical diagram 248

Section of pipe or moor grass; of bulrush 251

Human hip joint 252

Valves of veins 252

Built-up gun 253

Achromatic prisms and lens 255

Three levers 256

Arm holding ball 256

Beaver teeth 258

Narwhal with twisted tusk 259

Lower part of warrior ants’ nest, showing dome 260

Wasp using pebble as hammer 260

Cuban firefly 263

DR. R. S. WOODWARD _facing_ 276

Perforated sails for ships 292

Edison phonograph 312

TELEGRAPHONE 314 _and facing_ 314

GRAY TELAUTOGRAPH 315 _and facing_ 318

Hussey’s mower or reaper 321

Mergenthaler linotype, justifying wedges 323

Schuckers’ double-wedge justifier 324

Two wedges partly in contact, and fully in contact 325

Polarized light shows strains in glass 327

Stop-motion 330

Dexter feeding mechanism 331

Schumann’s “Traumerei” in musical score and on Pianola roll 334

Mechanism of Pianola 335

AUTOMATIC TELEPHONE 336 _and facing_ 336

Blenkinsop’s locomotive, 1811 345

Notes on loose cards in alphabetical order 350

Sectional bookcase, desk and drawers 351

Burke telegraphic code 353

Burke simplified telegraphic signals 354

Pupin long-distance telephony 367

Water-gauge direct and reversed 370

THOMAS ALVA EDISON _facing_ 374

Cube-root extractor 376

Square-root extractor 377

Sturtevant ventilating and heating apparatus 380

Bicycle suspended from axle 382

Telephones receiving sound through a beam of light 395

Selenium cylinder with reflector 398

Perforated disc yielding sound from light 399

SIR HENRY BESSEMER _facing_ 402

First Bessemer converter and ladle 406

New Ingersoll coal cutter 418

Drill steels 418

SCULPTOR AT WORK WITH PNEUMATIC CHISEL _facing_ 418

Haeseler air-hammer 419

Rock drill used as hammer 420

Little Giant wood-boring machine 420

Water lifted by compressed air 421

Harris system of pumping by compressed air 422

Hardie nozzle for painting by compressed air 423

Vacuum renovators for carpets and upholstery 424

Injector sand-blast, Drucklieb’s 425

Vertical receiver, inter- and outer-cooler 426

Concrete silo foundation 431

Concrete silo 432

MANSION IN CONCRETE, FORT THOMAS, KENTUCKY _facing_ 432

Wall of two-piece concrete blocks 434

Ransome bar for concrete 436

Corrugated steel bar 436

Thacher bar 436

Kahn bar 437

Hennebique armored concrete girder 437

Monier netting 437

Expanded metal diamond lath 438

Tree box in expanded steel 438

ROYAL BANK OF CANADA, HAVANA _facing_ 438

Lock-woven wire fabric 439

Column forms for concrete, Ingalls Building, Cincinnati 440

Section of chimney, Los Angeles, Cal. 441

Coignet netting and hook 442

Section of conduit, Newark, N. J. 442

Water culvert 443

River des Pêres Bridge, Forest Park, St. Louis 444

Memorial Bridge, Washington, D. C. 444

Francis vertical turbine wheel 446

5000 HORSE-POWER ALLIS-CHALMERS STEAM ENGINE _facing_ 448

Smoke-jack 449

POWER HOUSE, INTERBOROUGH CO., NEW YORK, exterior _facing_ 450

Schmidt superheater 451

POWER HOUSE, INTERBOROUGH CO., NEW YORK, interior _facing_ 452

De Laval steam turbine, sections 453

WESTINGHOUSE-PARSONS STEAM TURBINE _facing_ 454

Combustible gas from a candle 458

Taylor gas-producer 460

Four-cycle gas engine 463

Fire syringe 467

Sturtevant fan wheel, without casing 472

Sturtevant Monogram exhauster and solid base heater 473

NEW YORK CENTRAL R. R. ELECTRIC LOCOMOTIVE WITH FIVE-CAR

TRAIN _facing_ 476

ACKNOWLEDGMENTS

Aid in writing this volume is acknowledged in the course of its

chapters. The author’s grateful thanks are rendered also to Dr. L. A.

Fischer, of the Bureau of Standards at Washington, who has revised the

paragraphs describing the work of the Bureau; to Mr. C. R. Mann of the

Ryerson Physical Laboratory, University of Chicago, who corrected the

paragraphs on the interferometer; to Mr. Walter A. Mitchell, formerly of

Columbia University, New York, who revised most of the chapters on

measurement. Mr. Thomas E. Fant, Head of the Department of Construction

and Repair at the Navy Yard, Washington, D. C., gave the picture of the

model basin here reproduced. Mr. Walter Hough of the National Museum,

Washington, D. C., contributed a photograph of the Pomo basket also

reproduced here. Mr. John Van Vleck and Mr. Henry G. Stott of New York,

Mr. George R. Prowse and Mr. Edson L. Pease of Montreal, have furnished

drawings and photographs for illustrations of unusual interest. Mr.

George F. C. Smillie, of the Bureau of Engraving, Washington, D. C., Mr.

Percival E. Fansler, Mr. Ernest Ingersoll, and Mr. Ashley P. Peck, of

New York, have read in proof parts of the chapters which follow. Their

corrections and suggestions have been indispensable.

Professor Bradley Stoughton, of the School of Mines, Columbia

University, New York, has been good enough to contribute a brief list of

books on steel, supplementing the chapter on that theme written with his

revision. Had it been feasible, other chapters would have been

supplemented in like manner by other teachers of mark. In 1902 the

American Library Association published an annotated guide to the

literature of American history, engaging forty critics and scholars of

distinction, with Mr. J. N. Larned as editor. It is hoped that at no

distant day guides on the same helpful plan will be issued in the field

of science, duly supplemented and revised from time to time.

* * * * *

In the present volume the author has endeavored to include in his survey

the main facts to the close of May, 1906.

NEW YORK, September, 1906.

INVENTORS AT WORK

CHAPTER I

INTRODUCTORY

Inventors and discoverers are justly among the most honored of men. It

is they who add to knowledge, who bring matter under subjection both in

form and substance, who teach us how to perform an old task, as

lighting, with new economy, or hand us gifts wholly new, as the

spectroscope and the wireless telegraph. It is they who tell us how to

shape an oar into a rudder, and direct a task with our brains instead of

tugging at it with our muscles. They enable us to replace loss with

gain, waste with thrift, weariness with comfort, hazard with safety.

And, chief service of all, they bring us to understand more and more of

that involved drama of which this planet is by turns the stage and the

spectator’s gallery. The main difference between humanity to-day and its

lowly ancestry of the tree-top and the cave has been worked out by the

inventors and discoverers who have steadily lifted the plane of life,

made it broader and better with every passing year.

On a theme so vast as the labors of these men a threshold book can offer

but a few glances at principles of moment, to which the reader may add

as he pleases from observations and experiments of his own. At the

outset Form will engage our regard: first, as bestowed so as to be

retained by girders, trusses and bridges; next, as embodied in

structures which minimize friction, such as well designed ships; or as

conducing to the efficiency of tools and machines; or deciding how best

heat may be radiated or light diffused. A word will follow as to modes

of conferring form, the influence on form of the materials employed, and

the undue vitality of old forms that should long ago have bidden us

good-by. Structures alike in shape may differ in size. Bigness has its

economies, and so has smallness. Both will have brief attention, with a

rapid survey of new materials which enable a builder to rear towers or

engines bolder in dimensions than were hitherto possible.

Substance, as important as form, will next receive a glance. First a

word will be said about the properties of food, raiment, shelter,

weapons and tools. Then, the properties of fuels and light-givers will

be considered, as steadily improved in their effectiveness. How

properties are modified by heat and electricity will be remarked, with

illustrations from steels of new and astonishing qualities, and from

notable varieties of glass produced at Jena. A few pages will recount

some of the striking phenomena of radio-activity displayed by radium,

thorium and kindred substances, phenomena which are remolding the

fundamental conceptions of physics and chemistry.

A survey of form and properties, however cursory, must involve

measurement, otherwise an inventor cannot with accuracy embody a plan in

a working machine, or know exactly how strong, elastic, or conducting a

rod, a wire, or a frame is. Measuring instruments will be sketched,

their use delineated, and the results of precise measurement noted as an

aid to the construction of modern mechanism, the interchangeability of

its parts, the economy of materials and of energy in every branch of

industry. Next will follow a chapter noting tasks which Nature has long

accomplished, and which Art has still to perform, as in converting at

ordinary temperatures within the human body fuel energy into work.

Plainly, a broad field opens to future invention as it copies the

function of plants and animals; functions to be first carefully

observed, then explained and at last imitated with the least possible

waste of effort.

The equipment and the talents for invention and discovery are now

touched upon. First, knowledge, especially as the fruit of disinterested

inquiry; Observation, as exercised by trained intelligence calling to

its aid the best modern instruments; Experiment, as an educated passion

for building on original lines. Then, in the mechanical field, we bestow

a few glances at self-acting machines, at the simplicity of design which

makes for economy not only in building, but in operation and

maintenance. Either in designing a new machine, or in reaching a great

truth, such as Universal Development, there is scope for Imagination

upon which we next pause for a moment. A succeeding chapter outlines

how theories may be launched and tested, how analogy may yield a golden

hint, the profit in rules that work both ways, or even in doing just the

opposite of what has been done without question for ages past.

[Illustration: Copyright, 1906, by Park & Co., Brantford, Ontario,

Canada

BELL HOMESTEAD, BRANTFORD, ONTARIO, CANADA.

ALEXANDER GRAHAM BELL AND HIS DAUGHTER IN THE FOREGROUND.

HERE THE TELEPHONE WAS PERFECTED IN 1874.

Now the Home of the Bell Telephone Memorial Association.]

From this brief consideration of method we now pass to a few men who

have exemplified method on the loftiest plane; we come into the presence

of Newton, the supreme generalizer, and observe his patience and

conscientiousness, as remarkable as his resourcefulness in experiment,

in mathematical analysis. Even greater in experiment, while lacking

mathematical power, is Faraday, who next enlists our regard. This great

man, more than any other investigator, laid the foundations of modern

electrical science and art. Moreover he distinctly saw how matter might

reveal itself in the ‘radiant’ condition now engaging the study of the

foremost inquirers in physics.

Electricity has no instrument more useful in daily life, or in pure

research, than the telephone. Now follows a narration by its creator,

Professor Bell, of his photophone which transmits speech by a beam of

light. This recital shows us how an inventor of the first rank proceeds

from one attempt to another, until his toil is crowned with success.

Next we hear the story of the Bessemer process from the lips of Sir

Henry Bessemer himself, affording us an insight into the methods and

characteristics of a mind ingenious, versatile and bold in the highest

degree. An inventor of quite other type is next introduced,--Nobel, who

gave dynamite to the quarryman and miner, smokeless powder to the gunner

and sportsman. His unfaltering heart, beset as he was by constant peril,

marks him a hero as brave as ever fought hazardous and dreary campaigns

to a victorious close.

Many advances in mechanical and structural art have been won rather

through a succession of attacks by one leader after another, than by a

single decisive blow from a Watt or an Edison. A great band of

inventors, improvers, adapters, have accomplished notable tasks with no

record of such a feat as Bessemer with his converter, or Abbe with Jena

glass. A brief chapter deals with some of the principal uses of

compressed air, an agent of steadily increasing range. As useful, in a

totally different sphere--that of building material--is concrete,

especially as reinforced with steel. A sketch of its applications is

offered. Then follows the theme of using fuels with economy, of

obtaining from them motive powers with the least possible loss. This

field is to-day attracting inventors of eminent ability, with the

prospect that soon motive powers will be much cheapened, with incidental

abridgment of drudgery, a new expansion of cities into the country, and

the production of light at perhaps as little as one-third its present

cost. A page or two are next given to a few social aspects of invention,

its new aid and comfort to craftsmen, farmers, householders

comparatively poor. It will appear that forces working against the undue

centralization of industry grow stronger every day.

A closing word gives the reader, especially the young reader, a hint or

two in case he wishes to pursue paths of study the first steps of which

are taken in this book.

In 1900 was published the author’s “Flame, Electricity and the Camera,”

in which are treated some of the principal applications of heat,

electricity and photography as exemplified at the time of writing. That

volume may supplement the book now in the reader’s hands.

CHAPTER II

FORM

Form as important as substance . . . Why a joist is stiffer than a

plank . . . The girder is developed from a joist . . . Railroad

rails are girders of great efficiency as designed and tested by Mr.

P. H. Dudley.

[Illustration: A lens of ice focussing a sunbeam.]

One January morning in Canada I saw a striking experiment. The sun was

shining from an unclouded sky, while in the shade a Fahrenheit

thermometer stood at about twenty degrees below zero. A skilful friend

of mine had moulded a cake of ice into a lens as large as a reading

glass; tightly fastened in a wooden hoop it focussed in the open air a

sunbeam so as to set fire to a sheet of paper, and char on a cedar

shingle a series of zigzag lines. There, indeed, was proof of the

importance of form. To have kept our hands in contact with the ice would

have frozen them in a few minutes, but by virtue of its curved surfaces

the ice so concentrated the solar beam as readily to kindle flame.

Clearly enough, however important properties may be, not less so are the

forms into which matter may be fashioned and disposed. Let us consider a

few leading principles by which designers have created forms that have

economized their material, time and labor, and made their work both

secure and lasting. We will begin with a glance at the rearing of

shelter, an art which commenced with the putting together of boughs and

loose stones, and to-day requires the utmost skill both of architects

and engineers.

Strength and Rigidity.

Building in its modern development owes as much to improvement in form

as to the use of stronger materials, brick instead of clay, iron and

steel instead of wood. A stick as cut from a tree makes a capital

tent-pole, and will serve just as well to sustain the roof of a cabin.

For structures so low and light it is not worth while to change the

shape of a stick. By way of contrast let us glance at an office building

of twenty-five stories, or the main piers of the new Quebec Bridge

rising 330 feet above their copings. To compass such heights stout steel

is necessary, and it must be disposed in shapes more efficient than that

of a cylinder, as we shall presently see.

In most cases strength depends upon form, in some cases strength has

nothing whatever to do with form; if we cut an iron bar in two its

cross-section of say one square inch may be round, oblong, or of other

contour, while the effort required to work the dividing shears will in

any case be the same. But shearing stresses, such as those here in play,

are not so common or important as the tension which tugs the wires of

Brooklyn Bridge, or the compression which comes upon a pillar beneath

the dome of the national capitol. When we place a lintel over a door or

a window, we are concerned that it shall not sag and let down the wall

above it in ruin: we ensure safety from disaster by giving the lintel a

suitable shape. When we build a bridge we wish its roadway to remain as

level as possible while a load passes, so that no hills and hollows may

waste tractive power: levelness is secured by a design which is rigid as

well as strong. If a railroad has weak, yielding rails, a great deal of

energy is uselessly exerted in bending the metal as the wheels pass by.

A stiff rail, giving way but little, avoids this waste. To create forms

which in use will firmly keep their shape is accordingly one of the

chief tasks of the engineer and the architect.

[Illustration: Rubber strip suspended plank-wise, and joist-wise.]

[Illustration: Board doubled breadthwise through small semi-circle AB,

then edgewise through large semi-circle CD.]

Plank and Joist.

Forms of this kind, well exemplified in the steel columns and girders of

to-day, have been arrived at by pursuing a path opened long ago by some

shrewd observer. This man noticed that a plank laid flatwise bent much

beneath a load, but that when the plank rested on its narrow edge, joist

fashion, it curved much less, or hardly at all. Thus simply by changing

the position of his plank he in effect altered its form with reference

to the strain to be borne, securing a decided gain in rigidity. Let us

repeat his experiment, using material much more yielding than wood. We

take a piece of rubber eight inches long, one inch wide and one quarter

of an inch thick. Placing it flatwise on supports close to its ends we

find that its own weight causes a decided sag. We next place it

edgewise, taking care to keep it perpendicular throughout its length,

when it sags very little. Why? Because now the rubber has to bend

through an arc four times greater in radius than in the first

experiment. Suppose we had a large board yielding enough to be bent

double, we can see that there would be much more work in doubling it

edgewise than flatwise. The rule for joists is that breadth for breadth

their stiffness varies as the square of their depth, because the circle

through which the bending takes place varies in area as the square of

its radius. In our experiment with the rubber strip by increasing depth

four-fold, we accordingly increased stiffness sixteen-fold; but the

breadth of our rubber when laid as a joist is only one-fourth of its

breadth taken flatwise, so we must divide four into sixteen and find

that our net gain in stiffness is in this case four-fold.

[Illustration: Telegraph poles under compression. Wires under tension.]

Girders.

Here let us for a moment dwell upon the two opposite ways in which

strength may be brought into play, as either compression or tension is

resisted. An example presenting both is a telegraph pole, with

well-balanced burdens of wires. Its own weight and its load of wires,

compress it, as we can prove by measuring the pole as stretched upon

the ground before being set in place, and then after it is erected and

duly laden. Should this downward thrust be excessive, the pole would be

crushed and broken down. The strung wires are not in compression, but in

the contrary case of tension, and are therefore somewhat lengthened as

they pass from one pole to the next. Now observe a mass first subjected

to compression, and next to tension. In bearing a pound weight a rubber

cylinder is compressed and protrudes; when the weight is suspended from

this cylinder, the rubber is lengthened by tension. In each case the

effect is vastly greater than with wood or steel, because rubber has so

much less stiffness than they have.

[Illustration: Rubber cylinder.

Flattened by compression.

Lengthened by tension.]

Both tension and compression are exhibited in our little rubber joist,

which illustrates the familiar wooden support beneath the floors of our

houses. This form in giving rise to the girder has been changed for the

better. Let us see how. As the rubber joist sags between its ends, we

observe that its upper half is compressed, and its lower half extended,

the two effects though small being quite measurable. As we approach the

central line, A B, this compression and tension gradually fall to zero;

it is clear that only the uppermost and undermost layers fully call

forth the strength of the material, the inner layers doing so little

that they may be removed with hardly any loss. Hence if we take a common

joist and cut away all but an upper and lower flange, leaving just web

enough between to hold them firmly together, we will have the I-beam

which among rectangular supports is strongest and stiffest, weight for

weight. In producing it the engineer has bared within the joist the

skeleton which confers rigidity, stripping off all useless and

burdensome clothing. An I-beam made of rubber when laid flatwise over

supports at its ends will sag much; when laid edgewise it will sag but

little, clearly showing how due form and disposal confer stiffness on a

structure.

[Illustration: Rubber joist in section, compressed along the top,

extended along the bottom.]

[Illustration: Girder cut from joist.]

[Illustration: Rubber I-beam suspended flatwise, and edgewise.]

[Illustration: Simple girder contours.]

[Illustration: Girder contours simple and built up.]

[Illustration: Girder forms in locomotive draw-bars.]

Girders of steel are rolled and riveted together at the mills in a

variety of contours, each best for a specific duty, as the skeleton of a

floor, a column, or a part of a bridge. Their lengths, if desired, may

far exceed those possible to wood. Their principal simple forms are the

I-beam; T, the tee; L, the angle; C, the channel; and the Z-bar. Of

these the I-beam is oftenest used; its two parallel flanges are at the

distance apart which practice approves, they are united by a web just

stout enough not to be twisted or bent in sustaining its burdens. Crank

shafts of engines, to withstand severe strains, are built in girder

fashion; so are the side-bars of locomotives and the braces of steel

cars. Plates riveted together may serve as compound girders or columns

of great strength and rigidity. In the New York subway the riveted steel

columns which support the roof have a contour which enlarges at the

extremities.

[Illustration: 100,000 pound steel ore car built by the Standard Steel

Car Co., Pittsburg, for the Duluth, Missabe & Northern R. R. Of

structural steel throughout. Weight unloaded, 32,200 pounds.]

[Illustration: Section of standard bulb angle column, New York Subway.]

The Rail.

By all odds the most important girder is the rail in railroad service.

Let us glance at phases of its development in America, as illustrating

the importance of a right form to efficient service. At the outset of

its operations, in 1830, the Mohawk & Hudson Railroad, now part of the

New York Central & Hudson River Railroad, employed a rail which was a

mere strap of iron two and one half inches wide, nine sixteenths of an

inch thick, with upper corners rounded to a breadth of one and seven

eighths inches; it was laid upon a pine stringer, or light joist, six

inches square, and weighed about 14 pounds per yard. Thin as this rail

was, its proportions were adequate to bearing a wheel-flange which

protruded but half an inch or even less. Where the builders of that day

sought rigidity and permanence was in the foundations laid beneath their

stringers. Except upon embankments there were for each track two pits

each two feet square, three feet from centre to centre, filled with

broken stone upon which were placed stone blocks each of two cubic feet.

On the heavy embankments cross-ties were laid; these were found to

combine flexibility of superstructure with elasticity of roadbed, so

that they were adopted throughout the remainder of the track

construction and continue to this hour to be a standard feature of

railroad building.

[Illustration: Strap rail and stringer, Mohawk & Hudson R. R., 1830.]

It was soon observed that the surface of a track as it left the

track-maker’s hands, underwent a depression more or less marked when a

train passed over it. With a strap-iron rail this depression was so

great that engines were limited to a weight of from three to six tons.

Before long the strap form was succeeded by a rail somewhat resembling

in section the rail of to-day. Year by year the details of rolling

rails were improved, so that sections weighing thirty-five to forty

pounds to the yard came into service. These at length united a hard

bearing surface for the wheel-treads, a guide for the wheel-flanges, and

a girder to carry the wheel-loads and distribute them to the cross-ties.

Thereupon the weights of engines and cars were increased, leading, in

turn, to a constant demand for heavier rails. In 1865 a bearing surface

was reached adequate for wheel-loads of 10,000 to 12,000 pounds, the

rail weighing fifty-six to sixty pounds to the yard. But the metal was

still only iron, and wore rapidly under its augmented burdens. Then was

introduced the epoch-making Bessemer process and steel was rolled into

rails four and one-half inches high, of fifty-six to sixty-five pounds

to the yard, of ten to fifteen-fold the durability of iron. In design

the early steel rails were limber so that they rapidly cut the

cross-ties under their seats, pushing away the ballast beneath them.

Because they lacked height they had but little stiffness, one result

being that the spikes under the rails were constantly loosened,

exaggerating the deflection due to passing trains. Throughout the lines

every joint became low, and the rails took on permanent irregularities

under the pounding of traffic, dealing harmful shocks to the rolling

stock.

Dudley’s Track Indicator.

This was the state of affairs in 1880, when Mr. Plimmon H. Dudley

invented his track-indicator. This apparatus, placed in a moving car,

records by ever-flowing pens on paper every irregularity, however

slight, in the track over which it passes. When railroad engineers first

saw its records, they believed that the thing to do was to restore their

roads to straightness by the labor of track-men. It was abundantly

proved that the real remedy lay in using a rail of increased stiffness,

that is, a rail higher and heavier. Mr. Dudley, in the light of records

covering thousands of miles of running, added fifteen pounds to a rail

which had weighed sixty-five pounds, and gave it a height of five inches

instead of four and one half, while he broadened its upper surface. At a

bound these changes increased the stiffness of the section sixty per

cent., the gain being chiefly due to added height. Proof of this came

when his improved rail was found to be much stiffer than that of the

Metropolitan Railway, of London, which weighed eighty-four pounds to

the yard and had a base of six and three eighths inches, but a height of

only four and one half inches. In July, 1884, the Dudley rail was laid

in the Fourth Avenue viaduct, New York; so satisfactory did it prove

that in less than two years five-inch rails were in service on three

trunk lines. Then followed their introduction throughout America, their

smoothness and stability as a track giving them acceptance far and wide.

[Illustration: Photograph by F. M. Somers, Cincinnati, O.

PLIMMON H. DUDLEY

OF NEW YORK.]

The performance of the Dudley rail so impressed Mr. William Buchanan,

Superintendent of Motive Power for the New York Central Railroad that in

1889 he planned his famous passenger engine, No. 870, which entered upon

active duty in April, 1890. It carried 40,000 pounds upon each of its

two pairs of driving wheels, instead of 31,250, as did its heaviest

predecessor; its truck bore a burden of 40,000 pounds more; its loaded

tender weighed 80,000 pounds, making a total of 100 tons, an advance of

forty per cent. beyond the weight of the heaviest preceding engine and

tender. Mr. Buchanan’s forward stride has been worthily followed up.

Since 1890, passenger locomotives have nearly doubled in the weight

borne upon their axles, while tractive power has increased in the same

degree. Through express and mail trains have more than doubled in

weight, and their speeds have increased thirty to forty per cent. The

tonnage of an average freight train has been augmented four to six-fold,

with reduction of the crews necessary to keep a given amount of tonnage

in motion. This economy is reflected in a reduction of rates which are

now in America the lowest in the world, and which steadily fall. In

capacity for business united with stability of roadbed, mainly due to

stronger and stiffer rails and to adapted improvement in rolling stock,

railroad progress in the past fifteen years is equal to that of the

sixty years preceding. With rails increased to a weight of 100 pounds to

the yard there is shown, even in passing over the joints, an astonishing

degree of smoothness as contrasted with the jolting action of rails

comparatively low and light. Stiffness of rail reduces the destructive

action of service, originally enormous, upon both equipment and track,

lowering in a marked degree the cost of maintenance. Size of rail as

well as form plays a part in this economy. A passenger train weighing

378 tons has required 820 horse power on 65-pound rails, and but 720

horse power on 80-pound rails, the speed in both cases being 55 miles an

hour; it is estimated that with 105-pound rails 620 horse power would

have sufficed. In freight service Dudley rails have reduced the

resistances per ton from between 7 and 8 pounds to one half as much; a

further reduction, to 3 pounds, is in prospect. In passenger service,

with rails of unimproved type the resistance at 52 miles an hour is 12

pounds per ton; with Dudley rails this resistance for heavy trains is

not augmented when the speed rises to 65 or 70 miles an hour. Dudley

rails, and rails derived from their designs, are now in use on three

fourths of all the trackage of American railroads, effecting a vast

economy. Seventy-five years ago the DeWitt Clinton locomotive and tender

weighed only five sixths as much as the main pair of driving wheels,

boxes, axle, and connecting rods of the present Atlantic type of engine.

That such an engine can haul a heavy train at seventy miles an hour

largely depends upon the production of that simple and important element

in railroading, its rail.[1]

[1] Mr. Dudley’s rails, and those of other designers, are fully

illustrated and discussed in “Railway Track and Track Work,” by E.

E. Russell Tratman. Second edition. New York, Engineering News

Publishing Co.

[Illustration: Dudley rails.]

[Illustration: Steel cross-ties and rails.--Carnegie Steel Co.,

Pittsburg.]

In Ninth Street, Pittsburg, the rails of the traction line are for some

distance carried on steel ties similar in form, as here shown.

CHAPTER III

FORM--_Continued_. BRIDGES

Roofs and small bridges may be built much alike . . . The queen-post

truss, adapted for bridges in the sixteenth century, was neglected

for two hundred years and more . . . A truss bridge replaces the

Victoria Tubular Bridge . . . Cantilever spans at Niagara and Quebec

. . . Suspension bridges at New York . . . The bowstring design is

an arch disguised . . . Why bridges are built with a slight upward

curve . . . How bridges are fastened together in America and

England.

[Illustration: King-post truss. AK, king-post.]

Roofs and Bridges Much Alike.

Rails are girders used by themselves: girders are often combined in

trusses; of these much the largest and most important are employed for

bridges. There is now under construction near Quebec a cantilever bridge

whose channel span of 1,800 feet will be the longest in the world. See

page 29. It will take us a little while to understand how so bold a

flight as this was ever dared. We will begin with a glance at a truss of

the simplest sort, such as we may find beneath the roof of an

old-fashioned barn. A pair of rafters, AB and AC, are inclined to each

other at an obtuse angle, and are fastened to the horizontal beam, BC,

at B and C. Their apex, A, is joined to BC by the king-post, AK, which

binds the three strongly and firmly. This whole structure makes up a

triangle, and so does each of its halves, ABK and AKC. No other shape

built of straight pieces will keep its form under strain. Take in proof

say four pieces of lath and unite them with a freely turning pin at each

corner to make the frame, ABCD; it is easily distorted by a slight pull

or push; but insert cross-pieces, AC and BD so as to divide the square

into triangles, and at once the frame resists any strain not severe

enough to break the wood or crush its fastenings. As the roof presses

down the frame ABC, its sides, AB and AC, tend to slide away at their

lower ends, B and C, but this is prevented by the horizontal beam, BC,

which while it holds them in place is itself so stretched as to be held

level and straight. This calling into play of tension constitutes the

chief merit of the truss, and enables it in roofs and bridges to span

breadths impossible to simple beams bending downward under compressive

strains. Not only in houses, but in ships, the truss has great value; it

was introduced in this field by Robert Seppings of Chatham, in England,

about 1810. To resist the pressure of grinding ice, the “Roosevelt” is

built with trusses of great strength. She sailed in 1905, under

Commander Peary, for a voyage of Arctic discovery.

[Illustration: Frames of four sides. For rigidity diagonals are needed,

AC, BD.]

Were our barn roof flat instead of sloping to form a truss, its

supporting timbers, under compression, would have a decided sag from

which BC is free. When we fashion a small model of a king-post truss,

its sides, AB and AC, must be of metal or wood because they will be in

compression; the king-post, AK, and the base, BC, which will be under

tension, may be of rubber or cord. Always as in this case the parts of a

truss exposed to compression must be of rigid material. When a part may

be of cord, rope or wire, we know that it is resisting tension.[2]

[2] A model easily put together illustrates the truss in its

simplest form. Take a pair of wooden compasses, each half of which

is 15 inches long, such as are sold for blackboard use by the Milton

Bradley Co., Springfield, Mass., at 50 cents. At each tip fasten, by

the ring provided with the compasses, a chair castor such as may be

had at any hardware store. Join the tips of the castors by a rubber

strip. Holding the compasses upright, and applying pressure from the

hand, they will extend until the rubber will be so stretched as to

become almost perfectly horizontal. Various weights may in

succession be suspended from the compass-joint, replacing manual

pressure, and serving to measure the exerted tensions.

[Illustration: Cross-section of the “Roosevelt,” Commodore Peary’s new

Arctic ship. Reproduced by permission from the Scientific American, New

York.]

[Illustration: Pair of compasses stretch a rubber strip.]

Wrought iron exerts about as much resistance to compression as to

tension; so does steel. For this reason, and on account of their great

strength, they have immense value in building. Cast iron can bear only

about one sixth as much tension as compression, so that it is useful as

foundations, for the bed-plates of engines and machinery and the like,

but is unsuitable for girders. Wood is much stronger under tension than

compression; in white pine this proportion is as eight to one. In

designing timber bridges the strains are, therefore, as far as possible,

arranged for tension.

[Illustration: Queen-post truss.

DE, HO, queen-posts.]

[Illustration: Upper part of a roof truss.

Interborough Power House, New York.]

Let us now enter another barn, about one half wider than the first, and

look upward at its rafters. We see its roof sustained by timbers

disposed as DCMH, to avoid the undue weight necessary for a design

resembling that of our first roof, ABC. Instead of one upright post, AK,

as in that case, we have now two, DE and HO, called queen-posts,

sustaining the horizontal beam, CM. In large modern roofs the simple

queen-post is modified and multiplied, as in the main power house of the

Interborough Rapid Transit Company, West 59th St., New York. Returning

to our simple queen-post design, let us imagine a creek flowing between

walls spanned by DCMH; that truss and a mate to it, parallel at a

distance of say ten feet, would easily carry a roadway and give us a

bridge. A truss for a bridge must be much stronger than for a roof of

equal span, because a bridge has to bear moving loads which may come

upon it suddenly, giving rise not only to serious strains but to severe

vibrations, all varying from moment to moment.

[Illustration: Two queen-post trusses form a bridge.]

[Illustration: Palladio trusses.]

Palladio’s Long Neglected Truss.

The queen-post truss was remarkably developed by Palladio, a famous

Italian architect of the sixteenth century. Two of his designs, here

given in outline, are from his work on architecture published in 1570;

their contours, little changed, are in vogue to-day. Strangely enough

the trusses of Palladio, for all their merit, passed out of notice until

their principles were revived and improved by Theodore Burr, in 1804,

in a wooden bridge over the Hudson at Waterford, New York. This bridge

had spans respectively of 154, 160 and 180 feet, stretches impossible to

single wooden beams. Professor J. B. Johnson, an eminent engineer, says

that this is the most scientific design ever invented for an all-wooden

bridge; during fifty years it stood unrivaled as a model for highway

purposes in this country. The Burr bridges were usually covered in, so

as to resemble the roofs we began by inspecting. In a truss bridge each

part bounded by two adjacent uprights, as DOEH in the queen-post figure

on page 21, is a _panel_; every part under compression, as DO, HE, is a

_strut_, _post_, or _column_; every part subject to tension as DE, HO,

is a _tie_.

[Illustration: Burr Bridge, Waterford, N. Y.

DO, HE, struts. DE, HO, ties. DHEO, panel.]

In 1830 as the first American railroad train sped on its way, a new era

dawned for the bridge builder as well as for his neighbors. At once

sprang up a demand for bridges longer and stronger than those which in

the past had served well enough. A score of wagons laden with wheat or

potatoes were a good deal lighter than a locomotive followed by a train

of loaded freight cars. A market-wagon, too, could easily be taken

aboard a ferry-boat, but for an engine and its cars a bridge was

imperative, if the stream were not so wide as to forbid all opportunity

to the bridge builder. His response to the demands of the railroad was

two-fold. First in the use of metal instead of wood, beginning with iron

rods to bind together frames of timber. As iron became cheaper and its

value more and more evident, he employed it for additional parts of his

structure until at last he built the whole bridge of iron.

To-day good steel is so cheap that railroad bridges are seldom reared of

anything else. Besides using stronger materials, the designer has

gradually improved the form of his structure, not only in its parts but

as a whole, so that to-day, strength for strength, a bridge may be only

one tenth as heavy as a bridge of fifty years ago. Advances in form have

been due to experience as one type has been compared with another;

meanwhile the mathematicians have carried their analysis of strains as

far as the extreme complexity of their problems will allow, greatly to

the betterment of designs.

In building a bridge, as in rearing many other structures, girders of

various contours are used. In bridge building the I-beam is most

employed. When the roadway proceeds on the top chord, as DH, in the

queen-post figure, page 21, we have a deck bridge; when it is built on

the bottom chord, as CM, we have a through bridge.

[Illustration: HOWE TRUSS]

[Illustration: PRATT TRUSS]

The Burr Bridge Simplified by Howe and Pratt.

The Burr bridge of 1804, already mentioned, included an arch and was in

part sustained by struts projecting from abutments. These features were

omitted by William Howe in the bridge which he patented in 1840, and

which was, as far as is known, the first successor to a design of

Palladio in employing a simple truss for long spans. The Howe truss was

built of wood, except its terminal tie-rods, which were of iron; it has

been repeated thousands of times throughout the world. In 1844 Thomas

W. and Caleb Pratt patented a bridge which in design was the converse of

Howe’s. Its diagonals of iron were used in tension, while its vertical

struts of timber were in compression; in the Howe pattern the diagonals

were in compression, the verticals in tension. This plan, by shortening

the struts, diminished the cross-section necessary in a truss. When

wrought iron took the place of wood for bridges, the Pratt design became

the most popular of all, combining as it did more desirable features

than any of its rivals. To-day for long spans the Baltimore truss is

much in favor. Its stresses, that is, its resistances to change of form

under strain, are readily ascertained; the shortness of its panels means

strength; and its diagonals have the inclination which wide and varied

experience has shown most desirable. The roadway, it will be observed,

is upheld by sub-verticals, that is, by verticals which reach the floor

from half the height of a panel.

[Illustration: Diagram of Baltimore truss.]

[Illustration: Whipple Bridge.]

An important study concerns itself with the intensity and distribution

of strains, first in girders, next in trusses, and lastly, in bridges as

units, all with intent to ensure the best possible designs throughout.

In this field of inquiry the pioneer was Squire Whipple, a maker of

mathematical instruments in Utica, N. Y., who published in 1847 his

analysis of the strains in a truss bridge due to its own weight and to

its moving loads. With the laws of these strains in mind he devised

several bridges of great merit, the most noteworthy being reared in

1852 on the Rensselaer & Saratoga Railroad, seven miles north of Troy,

which did service until 1883; its sides or web system had ties extended

across two panels in double intersection.

In a long truss bridge, which in its entirety may be regarded as a

girder of the utmost size, the cross pieces between the main beams of

the structure are much less heavy than if continuous plates, of no more

strength. The original form of the Victoria Bridge at Montreal was that

of a continuous tube of iron, square in section; it has given place to a

truss bridge of five times greater capacity which weighs only twice as

much. (Illustrations of both on pages 27 and 28.)

Thus to lessen weight in comparison with strength is a matter of great

importance in a suspended structure, which must not only bear its own

weight, but carry heavy moving loads.

[Illustration: Simple cantilevers.

FG, HI, are first separate; then in contact; last are joined by a plank

laid above them.]

[Illustration: VICTORIA BRIDGE, MONTREAL.

Original tubular form designed by Robert Stephenson.]

[Illustration: VICTORIA BRIDGE, MONTREAL,

Rebuilt with trusses.]

[Illustration: CANTILEVER BRIDGE ACROSS THE ST. LAWRENCE, NEAR QUEBEC.

Total length, CF, 3300 feet. Channel span, DE, 1800 feet. Central truss,

AB, 675 feet.]

Advantages of the Cantilever, Arch, and Bowstring Designs.

In most cases a bridge crosses a valley or a river in a place which

permits the engineer to erect scaffolding to support his trusses until

they can be united and become self-sustaining. In some places this

course is denied; a river such as the Ohio or the Mississippi may have

to be spanned at a point where the waters in a single day may rise

forty feet, bearing along trees and timbers with destructive violence.

As a rule the difficulty is met by employing cantilever spans which

require no scaffolding for their construction. To understand their

principle let us suppose that on opposite banks of a creek we roll out

to meet each other the joists FG and HI, taking care that the parts over

the water shall always be lighter than the parts on land. When the

joists at last touch they are secured to each other as a continuous

roadway. Or, while they are at a moderate distance apart they may be

joined by a third timber laid across the gap from one to the other. In

practice the simple principle thus illustrated is developed and varied

in many ways, but in every application the one rule is that the trusses

as they stretch out from the two sides of a pier shall balance each

other, the shore ends being duly weighted down or safely anchored to

solid rock. And thus, at length, we come to the wonderful bridge, six

miles west of Quebec, whose channel span of 1,800 feet will be the

longest ever reared. See illustration, page 29. From the cantilever

arms, DA and BE, will be suspended the central truss, AB, of 675 feet. A

cantilever span may be much longer than a simple truss because on a

pier, as D of this bridge, a part, DA, of the whole span, DE, is

balanced either, as in this case, by a shore span, CD, or by a

corresponding part of the next span should that span not extend to the

shore but pass from one pier to another.

[Illustration: Kentucky river cantilever bridge]

The first cantilever bridge in America was designed by C. Shaler Smith

for the Cincinnati Southern Railroad, to cross the Kentucky River; it

was built in 1876-7.

[Illustration: Arch bridge, Niagara Falls]

Spanning the gorge of Niagara, close to the Falls, is an arch bridge of

840 feet in its central span, which, in its construction during 1898,

followed the plan originated by James B. Eads in building the St. Louis

bridge nearly thirty years before. As scaffolding was out of the

question in both cases, each bridge was built out from its piers on the

cantilever principle. An arch is sometimes disguised as a modified

bowstring, as in the Burr design of 1804, a horizontal tie connecting

the extremities of the arched rib and taking its thrust, dispensing with

the abutments demanded by an arch. In the chords of such a pattern the

strength comes as near to uniformity throughout as practical

considerations permit, avoiding the losses of early days when one part

of a bridge might be twice as strong as another. The bowstring was

adopted for the great span of 542-1/2 feet over the Ohio at Cincinnati

built in 1888, and for the span of 546-1/2 feet erected at Louisville in

1893. A bowstring 533 feet long, forming part of the Delaware river

bridge of the Pennsylvania Railroad, built in 1896, in Philadelphia, is

outlined on page 32. At Bonn, on the Rhine, there was completed in 1904

a bridge whose central span is a bowstring 616-1/4 feet long.

[Illustration: Bowstring Bridge, Pennsylvania R. R., Philadelphia.]

Suspension Bridges and Continuous Girders.

If we take the design of an arch bridge and turn it upside down we have

a contour such as that of the Williamsburg Suspension Bridge, opened in

1903 between Brooklyn and Manhattan, depicted on page 33. For the utmost

length this is the only available span; it brings into play the tensile

strength of wire, the strongest form that steel can take. A steel cable

of suitable diameter, if it had to support only itself, might safely be

three miles long. A suspension bridge has another advantage in employing

an anchorage to bear strains which would break down a simple truss

resting on piers. As first erected suspension bridges were liable to

extreme and harmful vibration, in many cases being shaken to pieces by

storms of no great violence. It was found that this vibration was

checked and that safety was ensured by introducing stiffening trusses

which, at the same time, benefited the bridge by distributing the load

uniformly throughout the sustaining cables.

[Illustration: WILLIAMSBURG BRIDGE, NEW YORK CITY.]

At Lachine, about eight miles west of Montreal, on the line of the

Canadian Pacific Railroad, a remarkable bridge crosses the St. Lawrence

river. Its design is that of a continuous girder of four spans, the two

side spans being 269 feet each in length, and the two others each 408

feet. This type is discussed by Mr. Mansfield Merriman and Mr. Henry S.

Jacoby in Part IV, page 30, of their work on Roofs and Bridges. One of

the advantages presented is that deflection under live load is less, and

stiffness greater than for simple, discontinuous girders, the harmful

effect of oscillation being thus diminished. Furthermore, less material

is required than for simple, discontinuous spans. Both these elements

of gain are brought out in placing a strip of rubber, AD, upon four

equidistant points of support, when we find that BC, the central third

of the strip sags less than either AB or CD, the first or last third.

Cutting off one-third of the whole strip we deprive the removed piece,

at its surface of separation, of the cohesion which did much to keep the

whole strip, before cutting, almost horizontal at that point. We take

AB, our short removed piece of rubber, and lay it at its ends on two

points of support; it now serves in a rough-and-ready way as a model of

a simple truss, all by itself; its decided sag shows it much less rigid

than when it formed a part of an unbroken and longer structure.

Continuous girders despite their advantages are seldom employed; they

are liable to serious difficulties; among these may be mentioned that

changes, often unavoidable, of level in piers and abutments cause them

to suffer great reversals of stress, always a source of danger;

furthermore, variations of length due to changes of temperature are, of

course, much greater and more troublesome to provide against than in the

case of discontinuous girders.

[Illustration: Continuous girder bridge, Canadian Pacific R. R.,

Lachine, near Montreal.]

[Illustration: Rubber strip supported at 4 points, and at 2 points.]

Best Proportions for Spans: A Slight Upward Curve is Gainful. Pins or

Rivets in Fastening.

[Illustration: Plate girder bridge.]

Whether spans are long or short, engineers are fairly well agreed as to

the best proportions for girders and panels. They consider that a girder

should have about one-twelfth to one-tenth as much depth as span; and

that the weight of a web should be about equal to that of its flanges.

They usually give panels twice as much depth as length, with a tendency

to increase the proportion of depth to length, in order to minimize the

deflections and oscillations which shorten the life of a structure. For

definite lengths of span, particular types of construction are

preferred; usually for lengths of from 20 to 125 feet, plate girders are

chosen; for spans of 125 to 150 feet riveted lattice trusses are built;

for spans of 150 to 600 feet pin-connected trusses are employed. Here we

reach the economical limit of a length for simple trusses; beyond 600

feet the engineer is obliged to have recourse either to a cantilever or

a suspension bridge.

[Illustration: Part of lattice girder bridge, showing rivets.]

Whatever the breadth of the stream or the chasm over which he is to

build a roadway, each case must be studied in the light of its special

circumstances. There must be due regard to business as well as to

engineering considerations; the designer will bear in mind that types of

parts customarily turned out at great steel works are procurable in less

time, and at less cost, than novel types requiring to be manufactured to

order. Then, in speed of construction, he will remember that a

pin-connected bridge can be built much faster than a riveted structure.

Furthermore, every part must be vastly stronger than ordinary duty

requires. Tempests and floods may suddenly arise; at any instant a

derailment or a collision may create a strain of the utmost severity;

and even under ordinary circumstances it must not be forgotten that

train loads grow constantly heavier because economy lies that way.

[Illustration: Upper shelf, unladen, has upward curve or camber.

Lower similar shelf is straightened by its load.]

One detail of bridge design is worth a moment’s attention. When a

book-shelf is a thin board, quite straight as manufactured, it sags in

the middle when fully burdened. This downward dip may be avoided by

making the shelf at first with a slight curve which brings the middle a

little higher than the ends. In bridge building a like curve, or camber,

is given to each span so that when fully loaded it will be level or

nearly so. In a span of 500 feet it is found that a rise of half a foot

at the centre is sufficient. In suspension bridges, for the sake of

strengthening the structure, the camber far exceeds this ratio.

[Illustration: Pin connecting parts of a bridge.]

In fastening together the parts of a bridge the usual American practice,

already mentioned, is to employ pins which pass through eye bars. In

England riveting is preferred, as shown in the figure of the lattice

truss, page 36. This difference in methods arose through the use of

materials which differed. In the construction of bridges the English

engineer started with the flanged girder of cast or rolled iron, or some

other form of stiff beam, and as bridges increased in size so as to

require the framing of a truss, his whole effort was directed toward

making that truss as much like the original flanged or box girder as

possible. The American engineer, on the other hand, had at first little

or no iron or steel to work with, and of necessity used wood. As the

necessary bridges were of considerable span, the only feasible method

was to pin together small pieces of wood so as to form a connected

series of triangles. To make rigid joints in wood was impracticable, and

indeed rigid joints were not desired, because the strength of wood is

slight when strains are applied in any direction other than that of the

fibres of the piece, and the pin joint insures just this line of action.

As a rule a riveted bridge requires more metal than a pin-connected

design, takes more time to build, but demands somewhat less skill. To

provide for changes in length as a bridge is subjected to variations of

temperature, friction rollers are used to support its extremities. In

the first suspension bridge at Niagara Falls, built by Roebling, a

little cement accidentally covered the friction rollers and prevented

them from turning; fortunately the structure escaped the destruction to

which it was thus exposed.

[Illustration: Bridge rollers in section and plan.

New York, Pennsylvania & Ohio R. R.]

We have now taken a rapid survey of some of the methods by which the

designer of bridges plans a structure which is at once safe and to the

utmost extent economical of material. Step by step he has discovered how

little steel he may use for designs all the bolder because his hand is

so sparing of weight. His success began in adopting the girder, which we

have seen to be in effect the working skeleton long concealed within the

common joist; the cantilever span near Quebec, which compasses 1,800

feet in its flight, has been dissected out of preceding burden bearers

in the same way. Its metal stands forth as so much sheer muscle kept to

the most telling lines, unencumbered by a single pound of idle

substance. A designer of such a fabric is an artist skilled in

disengaging from masses of material every ounce that can be wisely

removed. In some cases, as when Roebling linked together New York and

Brooklyn, a bridge is created as much a thing of beauty as of use, as

graceful as it is strong.[3]

[3] Mr. David A. Molitor has a chapter, copiously illustrated, on

the esthetic design of bridges, beginning page 11 in the “Theory and

Practice of Modern Framed Structures,” by Mr. J. B. Johnson and

other authors, New York, John Wiley & Sons. Eighth edition, revised

and enlarged. $10.00.

CHAPTER IV

FORM--_Continued_. WEIGHT AND FRICTION DIMINISHED.

Why supports are made hollow . . . Advantages of the arch in

buildings, bridges and dams . . . Tubes in manifold new services

. . . Wheels more important than ever . . . Angles give way to

curves.

Having glanced at methods by which forms, judiciously chosen, economize

the materials of buildings and rails, of bridges diverse in type, we

pass to further consideration of these and like shapes, to find that

they effect a saving in material while they make feasible a new boldness

of plan, and introduce new elements of beauty. We will also remark that

judicious forms prevent waste of energy as structures are either set in

motion, or serve to convey moving bodies. Incidentally we shall see that

well chosen shapes insure a structure against undue hurt and harm.

[Illustration: Square

Octagonal

16-Sided

Round

Girder sections.]

Hollow Columns and Tubes.

In lofty structures, the box girder is frequently employed as a column

or a beam because it has even greater rigidity than the I-beam; usually

it has four sides, but it may have eight, sixteen, or more, and thus

step by step we come to a hollow cylindrical column which has, indeed,

the best form that can be bestowed on supporting material. Chinese

builders learned its economy on the distant day when they adopted the

bamboo for their walls and roofs. Comparison with a solid stick of

timber of like weight and substance will show that an equal length of

bamboo is decidedly preferable. The inner half of a round solid stick

does comparatively little in holding up a burden; to remove that half is

therefore as gainful as to strip from a joist the timber surrounding its

working skeleton. At first the journals or axles of engines and large

machines, as well as the axles of railroad cars and the shafts of

steamships were solid; to-day, in a proportion which steadily increases,

they are hollow. The advantage of this form comes out when we take two

cylinders of rubber, alike in length and weight, one solid, the other

hollow. Supporting both at their ends, the hollow form sags less than

the solid form, proving itself to be the more rigid of the two.

[Illustration: Solid rubber cylinder sags much.

Hollow rubber cylinder sags less.]

[Illustration: Handle-bar of bicycle in steel-tubing.]

[Illustration: A sulky in steel tubing.]

[Illustration: A pneumatic hammer, steel tubing.]

[Illustration: Fishing-rod in steel tubing.]

[Illustration: Bridge of steel pipe.]

With like advantage seamless tubing is adopted for a broad variety of

purposes. It builds bicycles and sulkies which far out-speed vehicles of

solid frames; it is worked up into elevator cages, mangle rolls,

pneumatic tools, fishing-rods, magazine-rifle tubes, inking rollers,

farm machinery, poles, masts and much else where strength and lightness

are to be united. Steel tubing is readily bent into any needed contour,

even when of considerable diameter. Mr. Egbert P. Watson has pointed out

its availability for highway bridges of about forty feet span, no

professional bridge-builders being needed for their construction. Near

Saxonville, Massachusetts, a pipe-arch bridge, eighty feet long,

provides a roadway across the Sudbury River, while carrying within its

pipe a stream which forms part of the Boston water system. A bridge of

similar form, 200 feet long, spans Rock Creek in the City of Washington.

The Eads bridge crossing the Mississippi, at St. Louis, employs for each

span eight steel tubes of nine inches exterior diameter. Tubes large and

small have been strengthened by adopting the model of an old-fashioned

fire-lighter, or spill, a bit of paper rolled spirally as a hollow tube.

Blow sharply into it and you but tighten its joints. In like manner

tubes and pipes of metal are all the tighter when their seams are

spiral instead of longitudinal. An eager quest for combined strength and

lightness in the bicycle has ended in the choice of tubes spirally

welded.

[Illustration: Arch bridge of steel pipe,

Sudbury River, near Saxondale, Mass.]

[Illustration: Spiral fire-lighter.]

[Illustration: Spiral weld steel tube.]

Arches.

When builders of old began to rear masonry they repeated in stone or

brick the forms they had constructed in wood. Accordingly the lintels of

their doors and windows were flat. It was a remarkable step in advance

when the arch was invented, probably by a bricklayer, spanning widths

impossible to horizontal structures. A flat course of stone or brick

presses downward only; an arch presses sidewise as well as downward. It

is this sidewise thrust, calling into play a new resource, that gives

the arch its structural advantage. In modern masonry the boldest arch is

that of the bridge at Plauen, Germany, with its span of 295-1/4 feet.

Of pointed arches the chief sustain the walls of Gothic cathedrals; it

was to counteract the outward thrust of these arches that external

buttresses were reared, either solid, as at St. Remy in Rheims, or

flying, as at Notre Dame in Paris. The Saracenic arch, offering more

than half of a circle, is not so strong as the Roman arch, but it has a

grace of its own, fully revealed in the Alhambra, and in the

incomparable mosque at Cordova. A chain of small links, a watch-chain,

for example, freely hanging between two points of support strikes out a

catenary curve; this Galileo suggested as the outline for an arch in

equilibrium; it is adopted for suspension bridges.

[Illustration: Longest stone arch in the world, Plauen, Germany.]

[Illustration: Church of St. Remy, Rheims, France.

Section across buttressed choir.]

[Illustration: Curve of suspended chain.]

[Illustration: Dam across Bear Valley, San Bernardino County,

California.]

“The arch,” says Mr. William P. P. Longfellow in “The Column and the

Arch,” “was the great constructive factor in the architecture of the

Roman Empire; it added enormously to the builder’s resources in

planning, and to his means of architectural effect. It gave him the

means of spanning wide openings, and when expanded into the vault, of

covering great spaces; it habituated him to curved lines and surfaces.

Helped by it, and spurred by the new wants of the complex Roman

civilization, he enlarged the scale of his buildings and greatly

increased the intricacy of their plans. He used his new combinations

with a boldness and fertility of invention that have been the wonder of

the world from that age to ours, constructing on a scale that dwarfed

everything that had gone before except the colossal buildings of Egypt.

Under a new stimulus, and with new means of effect, Roman building

greatly outstripped that of the Greeks in extent, in variety, and

magnificence.”

An arch built on its side, with its convexity upstream, and its ends

braced against rocky banks, serves admirably as a dam. It has in many

cases withstood floods much higher than those expected by its designers.

Such dams must not be too long, or what is saved in thickness is more

than lost in length. Arches inverted are used in many places as gulleys

for drainage. Near Bristol, in England, they anchor the cables of the

Clifton Suspension Bridge, at a depth of eighty-two feet below the

surface of the ground. Many tunnels finished in masonry have outlines

which are two arches united, the lower arch being inverted. The Cloaca

Maxima, the famous sewer at Rome, is of this pattern; it is twenty-six

feet high, sixteen feet broad, and is now in its twenty-fifth century of

service.

[Illustration: Ferguson locking-bar pipe. East Jersey Pipe Co,.

Paterson, N. J.]

Circles and Other Curves.

From arches, built of parts of circles, let us pass to the circle

itself, and glance at the use of tubes of circular section as we begin

to consider how resistances to motion may be minimized. The use of the

bamboo not only for building, but for the carriage of water, began in

the remote past. As structural material it was light and strong as we

have noticed; laid upon the ground it was a ready-made water pipe of

excellent form. When trees were hollowed out to convey water, when clay

was modeled into tubes, the hollow cylindrical shape of the bamboo was

in the mind of the Asiatic artisan, to be faithfully copied. That form

has descended to all modern piping for water, steam, and gas, because

the best that a pipe can take. No other shape has, proportionately to

capacity, so little surface for friction inside or rust outside. A

locking-bar water pipe, devised by Mephan Ferguson, of Perth, Australia,

is made of two plates of equal width, curved into semi-circles which are

pressed at their ends into channel bars of soft steel. As the

locking-bars and joints are opposite each other, their joints can be

tightly closed by a simple machine which exerts pressure in a straight

line. This construction may be used not only for pipes, but for

hydraulic cylinders, air receivers, mud and steam drums, tubular boilers

and boiler shells where high pressures are to be withstood.

A steam boiler or other vessel under severe internal strains had best be

spherical if equality to resistance is particularly desired. Usually a

cylindrical shape is much more convenient, and no other is given to

simple steam boilers or to the tubes of water-tube or fire-tube boilers.

Tubes comparatively narrow, are readily manufactured without seam, so

that they may be quite safe though thin; large boilers of plates riveted

together, must be built of thick metal. It was estimated by Mr. F.

Reuleaux, the eminent engineer, that if such boilers could be made in

one continuous piece of metal by the Mannesmann process, so successful

in tube-making, an economy in weight of at least one third would be

feasible.

[Illustration: Hand-hole plates.

Erie City water-tube boiler.]

In water-tube boilers a gainful departure from the circular form in a

detail of their design is worthy of notice. In order that their tubes

may be kept sound and clean they are rendered accessible by hand-holes

which pierce the front and back of the boiler. Usually these hand-holes

and their covers are round, a form which makes it necessary to put the

cover outside the boiler where even a good joint, well stayed, may leak

or give way under a pressure which tends to force apart the cover and

its seat. In the Erie City boiler the covers are elliptical; they are

readily passed through the hand-holes so as to rest not on the outside,

but on the inside, of the boiler, where the steam pressure makes their

joints all the tighter. A further advantage is that each elliptical

plate is large enough to give access to two tubes instead of one,

lessening the lines of juncture along which leakage may occur.

Wheels.

It was a memorable day when first a round log or stick was thrust under

a burden, easing its motion and leading to the wheel by piecemeal

improvements. A section cut off from the end of a round log is to-day

the wheel for ox-carts in China and India. In its crudest form a roller

enables a man to drag a load instead of carrying it, and he can readily

drag much more than he can carry. Wheelwrights of old soon found that a

wheel need not be solid, that strong spokes, a sound rim, and a metal

tire embody the utmost strength and lightness. Roller and ball bearings

much extend the benefits of simple wheels; they lessen friction in the

best typewriters, bicycles, and elevators; in wagons, carriages, and

automobiles roller bearings are so helpful that their use should be

universal. Of notable efficiency is the Hyatt bearing, formed by winding

a steel strip into a spiral roller. This device has a flexibility which

enables it to conform to irregularities of motion much better than can a

solid cylinder.

[Illustration: Bullock cart with solid wheels.]

For machinery the wheel is indispensable. The hand does its work chiefly

in moving to and fro, as in sawing and whittling. Machines outdo manual

toil by moving swiftly and continuously in a circle: instead of the

smoothing iron we have the mangle, boards are planed by rotary knives,

timber is divided by circular saws, and the steam turbine is displacing

the steam engine which every moment has to check the momentum of huge

reciprocating masses. Noteworthy in this regard is the perfecting press

which prints a newspaper from a continuous roll, as contrasted with the

old machine which demanded for each impression a distinct series of to

and fro movements. The Harris Rotary Press for job printing is of like

model. It feeds itself with 6,500 sheets an hour, printing from a

stereotype or an electrotype curved upon its cylinder. The lathe, simple

enough a century ago, has been developed into machines of great

complexity, power, and variety, all with the original rotary mandrel as

their essential feature. Milling machines, steadily gaining more and

more importance, employ rotary cutters which dispense with the manual

chipping and filing of former days.

[Illustration: Section--A B

Ball thrust collar bearing.

Ball Bearing Co., Philadelphia.]

[Illustration: Rigid bearings for driving axles of automobiles.

Ball Bearing Co., Philadelphia.]

[Illustration: Hyatt helical roller bearing.]

[Illustration: Hyatt rollers supporting an axle.]

[Illustration: Treads and risers joined by curves.]

Angles Replaced by Curves.

Wood as commonly hewn, sawn, and planed; bricks as usually molded;

stone as it leaves an ordinary hammer, all have flat sides and square

edges. Hence it has been easiest to build walls and floors which meet at

right angles, and to leave sharp corners on outer walls, windows,

doorways, and chimneys. This is being changed for the better; in

staircases the boards on which we tread and those which join them

together now meet in smooth curves; so do the walls of rooms as they

reach ceilings and floors, conducing to ease and thoroughness in

sweeping and cleansing. In outer walls, in doorways and windows, similar

curves reduce liability to hurt and harm. A wagon wheel easily knocks

pieces from an angle of brickwork; it makes little impression on bricks

retiring from the street line in a sweeping curve, as in the Madison

Square Garden, New York. Factory chimneys have long been built round

instead of square; to-day in the best designs the ducts to a chimney are

also freely curved. In blast furnaces this is the rule for every part of

the structure, ensuring gain in strength, lessening resistance to the

flow of gases, and thus saving much fuel. When waterpipes varying in

diameter are joined, the junction should be a gradual curve, otherwise

retarding eddies will arise, wasting a good deal of energy; the same

precaution is advisable in laying pipes for steam or gas. The elbows of

pipes for gas, steam or water exert the least possible friction when

given the utmost feasible radius. All the various parts of heavy guns

are curved, since any sharpness of angle at a joint brings in a hazard

of rupture under the tremendous strains of explosion.

[Illustration: Corner Madison Square Garden, Madison Avenue and 26th

Street, New York.]

[Illustration: Two pipes with funnel-shaped junction.]

Embossing and stamping machines may either decorate a sheet of note

paper or make a tub from a plate of steel. Whatever their size these

machines have the edges of their dies nicely rounded, so as to avoid

tearing the material they fashion. To ensure the utmost strength in the

machines themselves they are contoured in ample curves. In hydraulic

presses, subjected to strains vastly greater, the same shaping is

imperative, otherwise a cylinder may part abruptly with disastrous

effect. So, too, in the manufacture of magnets and electro-magnets,

their terminals are well rounded to ensure the closest possible

approach to uniformity of field and of working effect.

A glance at a warship discovers her varied use of curves in defence; to

deflect assailing shot and shell, her plates are given bulging lines,

her turrets are built in spherical contours, and her casemates are

convex throughout. On much the same principle fortifications are

rendered bomb-proof, or rather bomb-shedding; while outworks are so

inclined that bombs fall to distances at which they do little or no

harm. As in war so in peace; there is gain in building breakwaters with

an easy curve; to give their masonry and timbers a perpendicular face

would be to invite damage, whereas a flowing contour like that of a

shelving beach, slows down an advancing breaker and checks its shock. In

rearing lighthouses to bear the brunt of ocean storms the outline of a

breakwater is repeated to the utmost degree feasible. Often, however,

the base supporting a lighthouse is too small in area for such an

outline to be possible.

CHAPTER V

FORM--_Continued_. SHIPS

Ships have their resistances separately studied . . . This leads to

improvements of form either for speed or for carrying capacity . . .

Experiments with models in basins . . . The Viking ship, a thousand

years old, of admirable design . . . Clipper ships and modern

steamers. Judgment in design.

Forms of Ships Adapted to Special Resistances.

In giving form to a ship a designer has a three-fold aim,--strength,

carrying capacity and speed. Strength is a matter of interior build as

much as of external walls; it is conferred by girders, stays and

stiffeners which we have already considered, so that we may here pass to

the general form of the hull, which decides how much freight a ship may

carry, and, to a certain extent, how fast she may run. A ship is the

supreme example of form adapted to minimize resistance to motion; its

lesson in that regard will be the chief theme of this chapter. Until the

close of the eighteenth century the resistance to the progress of a ship

was regarded as a single, uncompounded element, plainly enough varying

with the vessel’s speed and size. It was Marc Beaufoy, who first in 1793

in London, pointed out that a ship’s resistance has two distinct

components; first, friction of the shell or skin with the water through

which the vessel moves, dependent upon the area of that skin; second,

resistance due to the formation of waves as the ship advances, dependent

upon the speed of the vessel and the shape of her hull. Other

resistances have since been detected, but these two are much the most

important of all; each varies independently of the other as one ship

differs from another in form, or as in the same ship one speed is

compared with another. To take a simple case: a ship’s model of a

certain form, of perfectly clean skin, is towed at various speeds and

the pull of the tow-line is noted; then the same model with its skin

roughened and covered with marine growths is towed at the same speeds,

and much greater pulls are observed in the tow-line. The wetted surface

is the same in the two series of experiments, the speeds correspond

throughout, and the increase of resistance due to a roughening of

surface can only mean that the friction between the water and the

submerged skin has increased. Next we take a model of certain form and

definite size, and a second model having the same area of wetted surface

but a different form; we tow both models at the same speed to find that

one requires a decidedly stronger pull than the other. This difference

cannot be due to frictional resistance of surface, for this is the same

in both models, therefore it must be due to the increased resistance

offered by the water as it is pushed aside, a resistance measurable in

the created waves. Mr. Edmund Froude, an eminent English authority,

says:

“For a ship A, of the ocean mail steamer type, 300 feet long and 31-1/2

feet beam and 2,634 tons displacement, going at 13 knots an hour, the

skin resistance is 5.8 tons, and the wave resistance 3.2 tons, making a

total of 9 tons. At 14 knots the skin resistance is but little

increased, namely 6.6 tons; while the wave resistance is nearly double,

namely, 6.15 tons. Mark how great, relatively to the skin resistance, is

the wave resistance at the moderate speed of 14 knots for a ship of this

size and of 2,634 tons weight or displacement. In the case of another

ship B, 300 feet long, 46.3 feet beam, and 3,626 tons displacement--a

broader and larger ship with no parallel middle body, but with fine

lines swelling out gradually--the wave resistance is much more

favorable.[4] At 13 knots the skin resistance is rather more than in the

case of the other ship, being 6.95 tons as against 5.8 tons; while the

wave resistance is only 2.45 tons as against 3.2 tons. At 14 knots there

is a very remarkable result in this broader ship with its fine lines,

all entrance and run and no parallel middle body:--at 14 knots the skin

resistance is 8 tons as against 6.6 tons in ship A, while the wave

resistance is only 3.15 tons as compared with 6.15 tons. The two

resistances added together are for B only 11.15 tons, while for A, a

smaller ship, they amount to 12.75 tons.”

[4] The entrance is that part of the ship forward where it enters

the water and swells out to the full breadth of the ship; the run is

the after part from where the ship begins to narrow and extending to

the stern. A ship may consist of only entrance and run; it may have

a middle body of parallel sides between the entrance and run. Such a

middle body is discussed by Lord Kelvin in “Popular Lectures and

Addresses,” Vol. III, Navigation, p. 492.

Experimental Basins.

These figures show that a designer must bear in mind the speed at which

this ship is to run; they prove that he may choose one form to minimize

friction, or another form if he particularly wishes to bring wave-making

resistance to the lowest possible point. Forms of these two kinds are

readily studied when represented in models 12 to 20 feet in length towed

through tanks built for the purpose. Experiments of this kind were

undertaken as long ago as 1770, in the Paris Military School; the

methods then inaugurated and copied in London at the Greenland Docks

were greatly improved by Mr. William Froude in a tank which he

constructed at Torquay in England, in 1870. His modes of investigation,

duly adopted by the British Admiralty, and after his death continued by

his son, Mr. Edmund Froude, have created a new era in ship design.

To-day in Europe and America there are eleven such tanks as Mr.

Froude’s, all larger than his and more elaborate in their appliances. In

addition to learning the behavior of models diverse in type, Mr. Froude

worked out the rules which subsist between the performance of a model

and that of a ship of like form; these he brought to proof in 1871 when

he towed Her Majesty’s Ship Greyhound, and verified his estimates in

towing its model. The rules concerned, known as those of mechanical

similitude, are given in detail by Professor Cecil H. Peabody in his

“Naval Architecture,” page 410. While experiments become more and more

valuable as one refinement succeeds another, there is always much well

worth knowing to be learned from the actual behavior of a vessel as she

takes her way through a canal, a shallow river, or the storm-beaten

stretches of the sea.

The experimental tank of the United States Navy at Washington, is 470

feet long, 44 broad, and 14-1/2 deep; it is arranged for models 20 feet

in length. See the page opposite. The towing carriage is a bridge

spanning the tank just above the water; it is a riveted steel girder.

The towing mechanism, of massive proportions, is driven by four electric

motors of abundant power. A double set of brakes brings the carriage

gradually and quietly to rest from a high speed. A self-acting recorder

measures both speed and resistance. Ship builders may have models built

by the Bureau in charge, that of Construction and Repair of the United

States Navy Department, and have these models towed at any desired

speeds, paying simple cost.

[Illustration: MODEL BASIN, U. S. NAVY YARD, WASHINGTON, D. C.]

It was in 1880 that the lessons of towing experiments with models began

to be adopted in practice. As a result the forms of steamers have been

greatly improved. Originally their lines were taken from those of

sailing vessels but, as dimensions grew bolder and speeds were

increased, it became clear that steamers demanded wholly different lines

of their own. These lines, fortunately, may be plainly disclosed in

experiments with a model, because a steamer usually runs on an even

keel, in which position a model is easily driven through a tank. A

sailing vessel, on the contrary, is nearly always heeled over by the

wind so that it seldom runs on an even keel; tank experiments,

therefore, avail but little for the improvement of its lines. Even were

the model inclined at various angles in one test after another, sails

must be omitted, with their influence on steering, their lifting and

burying effects, often extreme.

[Illustration: 1. Starboard Side. 2. Horizontal Sections. 3. Vertical

Sections. 4. Central Longitudinal Section. 5. Part of the Gunwhale

inside, with its Skirting in Front and in Section. 6. _Section through

AB._ 7. Bird’s Eye View.

THE VIKING SHIP.]

A Viking Ship a Thousand Years Old.

A thousand years ago the Vikings of Norway roved the seas in boats of a

form which is admired to-day. To those hardy adventurers swiftness and

seaworthiness meant nothing less than life and victory, their eyes

perforce were keen to note what craft sped fastest through the water,

what new curves kept waves from coming aboard. Perchance as they refined

upon keel and rib they took golden hints from the shapes of gulls and

fish. To be sure, long before science was dreamt of, they had to work by

rule-of-thumb, but the thumb was joined to brains that did honor to

human nature. On page 56 is illustrated the Viking Ship unearthed early

in 1880 at Godstad, near Sandefjord in Norway, in a mound where,

according to tradition, a king and his treasure had been buried. It is

the most complete and the best preserved vessel of ancient date in

existence. It is fully described and pictured in “The Viking Ship,” by

Mr. N. Nicolaysen, a work published in 1882 by Mr. Albert Cammermeyer,

Christiania. Mr. Nicolaysen regards the vessel as having been built

about A. D. 900, for use in war by the great chieftain whose tomb it

became. The ship was 65 feet, 10 inches long, on the keel; with an

extreme length over all of 78 feet, 1 inch; amidships it was 16 feet, 9

inches; its depth amidships from the top of the bulwarks to the keel was

3 feet, 11-1/4 inches. The material throughout was pine. The helm, a

plank shaped like a broad oar, was fastened to the side of the vessel.

In accordance with the number of its oars and shields this ship must

have had a crew of sixty-four, besides these came the steersman, the

chieftain and probably a few more of his companions, making a total, in

all likelihood, of seventy to be carried by her. Says Mr. Nicolaysen:

“In the opinion of experts this must be deemed a masterpiece of its

kind, not to be surpassed by aught which the shipbuilding craft of the

present age could produce. Doubtless, in the ratio of our present ideas,

this is rather a boat than a ship; nevertheless in its symmetrical

proportions, and the eminent beauty of its lines, is exhibited a

perfection never attained until after a long and dreary period of clumsy

unshapeliness, when it was once more revived in the clipper-built craft

of the nineteenth century.”[5]

[5] A detailed description of the Viking Ship is given in the

“Transactions of the Institute of Naval Architects”. (London), Vol.

XII, p. 298.

[Illustration: CLIPPER SHIP “YOUNG AMERICA.”

Length of deck, 235 feet. Beam molded, 40 feet, 2 inches. Depth of hold,

25 feet, 9 inches. Tonnage, 2900.]

Clipper Ships and Modern Steamers.

Thirty to sixty years ago much of the world’s commerce was borne by

clipper ships. In all likelihood as good lines as ever went into a

vessel of this kind were displayed in the Young America, outlined on

page 58, built in 1853 for California and East India trade. She once ran

from New York to San Francisco in 103 days, and from San Francisco to

New York in 63 days, records which have never been excelled. Her deck

length was 235 feet; her depth of hold 25 feet, 9 inches; her moulded

beam was 40 feet, 2 inches; her displacement was 2,713 tons. The lines

worthiest of remark in her design are the diagonals and buttocks,

together with her easy entrance and run. Most clipper ships were fuller

forward than aft; this had two advantages: first, when forward burdens,

anchors and the like, tended to an undue settling down at the head, it

was well to increase the buoyancy forward; second, towing experiments

prove that a form slightly fuller forward than aft offers less

resistance than the reverse. This shape was hit upon by the old-time

designers, doubtless as a result of many a shrewd experiment.

In the early days of steamships, hollow or somewhat concave water lines

forward were in favor. Experiments with models have demonstrated that

for boats so full in section as to be nearly square, it is best to have

forward lines which are straight or nearly so. Recently it has been

shown that at high speeds, with a midship section nearly semicircular,

resistance is a little lessened by very slightly hollowing the water

lines forward.

If a steamer is to have the utmost speed, as the Kaiser Wilhelm II,

outlined on page 60, her design will be very unlike that of a vessel

required to carry as much cargo as possible at a moderate or low speed,

as in the case of the steamship sketched on page 61. The dimensions of

the Kaiser Wilhelm II are:--length over all, 706-1/2 feet; beam, 72

feet; depth, 29 feet, 6-1/4 inches; displacement, 29,000 tons; speed,

23-1/2 knots; indicated horse power, 38,000. As we compare with her

details of form the general features of our cargo carrier, page 61, we

observe in this freighter the full form of its water lines, its almost

straight and blunt entrance forward; we also notice that the lower part

of the bow has been cut away to avoid a reversal of curves which would

create an eddy with its consequent increase of resistance. Further we

may remark the squareness of the midship section, which means carrying

capacity at its maximum, together with the long parallel middle body,

little resisted by the water, ending aft in buttocks and water-lines

quickly turned. This is a twin-screw ship: of length 358 feet, 2 inches;

beam, 46 feet; draft, 23 feet; depth from shelter deck, 34 feet, 8

inches; displacement, 8,270 tons; speed, 9 to 10 knots.

[Illustration: STEAMSHIP KAISER WILHELM II.

Length over all, 706 feet, 8 inches. Beam, 72 feet. Draft, 29 feet, 6.3

inches. Displacement, 29,000 tons. Indicated horse-power, 38,000. Speed,

23.5 knots.]

[Illustration: TWIN-SCREW CARGO STEAMER.

Length, 358 feet. Beam, 46 feet. Draft, 23 feet. Displacement, 8270

tons.]

[Illustration: U. S. TORPEDO-BOAT DESTROYER.

Length over all, 246 feet. Beam, 22 feet, 3 inches. Displacement, 489

tons. Speed, 30 knots.]

A good designer has an easy task in drawing lines for a freighter in

which the weight of hull, machinery and coals may be only 40 per cent.

of the displacement, leaving 60 per cent. for earning space. Contrast

this with an Atlantic flyer, where but 5 per cent. may remain for cargo.

Here the designer’s problems are difficult indeed, and the chief way out

of them is to enlarge his ship as much as he dares, for the bigger

his vessel, its form and speed unchanged, the less will be its

resistance as compared with displacement. But to an increase of size

there are hard and fast bounds; first, those imposed by the shallowness

of channels and harbors; while the depth of a ship is thus restricted,

its length may be somewhat extended with safety and gain; to increase of

beam there are distinct and moderate limits, to overpass them means that

the ship will follow the wave contour of a heavy sea so closely as to

have a quick, jerky and dangerous motion.

[Illustration: Cross-sections of ships]

Judgment in Ship Design.

To design a ship in this case and every other is plainly a matter of

compromise, a quest of the optimum by a balancing of demands for safety,

strength, speed, capacity, handiness, good behavior in a sea-way, so

that each invested dollar may in the long run earn the largest return

possible. Excellent examples of judicious design are the best passenger

steamers plying between Europe and New York. Usually their section

amidships is like that of a cargo vessel, but for a special reason.

Within the freighter’s walls the greatest feasible cross-section must be

created; so that the shape is box-like; in a high-speed passenger ship

the form is also square, because harbors are shallow; were they less

shallow the designer would choose a midship section somewhat

semicircular in contour. Were our harbors deepened, the easy sections of

the first transatlantic steamers could be repeated in their gigantic

successors of to-day, with increased speed for each horse power

employed.

What a designer can do when his aim is swiftness at the expense of all

other considerations, is shown in the lines of the torpedo-boat

destroyer, page 62. Its length over all is 246 feet; length at water

level, 240 feet, 10 inches; beam, 22 feet, 3 inches; mean draft, 6 feet,

1-1/2 inches; displacement, 489 tons; speed, 30 knots. It is interesting

to contrast, on page 63, the cross-section amidships of this vessel,

with similar lines of three other typical vessels described in this

chapter.[6]

[6] In writing these pages on the forms of ships I have been much

indebted to Mr. Harold A. Everett, Instructor in Naval Architecture,

Massachusetts Institute of Technology, Boston.

G. I.

CHAPTER VI

FORM--_Continued_. SHAPES TO LESSEN RESISTANCE TO MOTION

Shot formed to move swiftly through the air . . . Railroad trains

and automobiles of somewhat similar shape . . . Toothed wheels,

conveyors, propellers and turbines all so curved as to move with

utmost freedom.

Projectiles and Vehicles of Like Pattern.

While ships are much the largest structures built for motion, and

therefore meet resistances which the designer must lessen as best he

may, other moving bodies, small as compared with ships, encounter

resistances so extreme that their reduction enlists the utmost skill and

the most careful study. Speeds vastly higher than those of ships are

given to projectiles. A ball leaving a gun muzzle with a velocity of

3,410 feet a second, as at Sandy Hook in January, 1906, suffers great

atmospheric resistance, overcome in part by the shot having a tapering

or conoidal form. Indians long ago stuck feathers obliquely into arrows

so as to keep flight true to its aim by giving shafts a spiral motion;

an attendant advantage being to lengthen flight. The same principle

appears in rifling, that is, in cutting spiral grooves in the barrels of

firearms large and small, a missile receiving a spinning motion through

its base, a thin protruding disk of soft metal, forced into the grooves

by the explosive. At first the grooves in firearms were straight with

intent to preclude fouling; spiral grooves were introduced by Koster of

Birmingham about 1620. Delvigne, a Frenchman, devised a lengthened

bullet narrower than the bore so as to enter freely, under the pressure

of firing it completely filled the bore, rotating with great velocity as

it sped forth.

[Illustration: Racing automobile. Wedge front and spokeless wheels.]

Now that railroad speeds are approaching those of projectiles, the

outlines of trains are resembling those of shot and shell. In the

experiments with very fast trains at Zossen, in Germany, October, 1903,

each car had a paraboloidal front, much diminishing the resistance of

the air. Racing automobiles are usually encased in a pointed shell which

parts the air like a wedge; their wheels, too, are supported not by

spokes, but by disks having no projections. As electric traction becomes

more and more rapid in its interurban services, the cars will

undoubtedly be shaped to lessen atmospheric resistance. Especially is

this desirable in a tunnel service, such as that of the New York Subway,

where the resistances are extreme for the same reason that a boat in a

canal is harder to draw than if in water both broad and deep. Just as in

ship-design, it is in sharpening the front and rear of a car or a train

that most economy is feasible; the friction at the sides cannot be much

lessened except, in the case of a train, by joining each car to the next

by a vestibule such as that of the Pullman Company.

Electric traction finds gain in a track having in places a decided

inclination. In the monorail line between Liverpool and Manchester a

downward dip in the line at each terminal quickens departure, and in

arrival aids the brakes by checking speed on the up-grade. In the swift

motion of ordinary machinery the resistance of the air is a source of

considerable loss. By encasing a heavy flywheel in sheet iron so as to

present a smooth surface to the atmosphere, M. Ingliss has saved 4.8 per

cent. of the energy of a 630 horse power engine.

[Illustration: Bilgram skew gearing.]

Gearing: Conveyors.

In the simplest machines motion may be transmitted by wheels in contact,

faced with adhesive leather, rubber, or cloth. Teeth, however, are

usually employed; as wear takes place they permit a little play, a

slight looseness, which contact wheels altogether refuse. Toothed wheels

have the further advantage that they do not slip, their motion is

positive. How teeth may best be contoured involves nice questions in

geometry. They should always push and never grind each other, and should

move with the least possible friction. In some ingenious designs the

teeth of any one particular wheel of a series will enmesh with the teeth

of any other wheel, no matter how much larger or smaller. Bevel gears

cut by Mr. Hugo Bilgram, of Philadelphia, turn with hardly any friction

whatever, although in some wheels the teeth run askew, or are sections

of cones which do not meet at their apices. The Bilgram gear cutter, and

the Fellows’ gear shaper which turns out plain gear, exert a to and fro

planing action. Ordinary gears are cut on milling machines by rotary

cutters, or may be manufactured on a Bliss press without cutting the

original lines of fibre. The importance of accurate and easy-running

gears increases steadily; they are, for example, applied to steam

turbines whose velocity must be reduced in the actuation of ordinary

machines. Automobiles and bicycles also demand reducing gear running

with the utmost freedom.

[Illustration: Grain elevator.]

[Illustration: Robins conveying belt of rubber moved on rollers.]

The grain elevator, invented many years ago, is the parent of manifold

conveyors of coal, lime, ore or aught else. Their receivers have links

shaped so as to extend for hundreds of feet as continuous belts. Link

belting may be had in detachable sections, fitting each other at secure

hinges which allow free motion.

The _Augustin B. Wolvin_, a typical ore-carrier on the great lakes, is

56 feet in depth; its hold is curved to allow a clam-shaped bucket to

seize ten tons of ore at each dip. It is probable that at no distant day

rapid transit in cities will employ continuous moving platforms, just as

conveyors and telpherage systems are taking the place of the

discontinuous transport of grain, coal, cotton, ore, and heavy

merchandise.

[Illustration: Ewart detachable link belting.]

Propellers.

The screw, an inclined plane wound about an axis, forms the propeller

for steamships and many steamboats. There is a good deal of debate as to

the principles which should decide its best lines. Here evidently is a

field which will handsomely repay thorough investigation. The power

expended in steamships, whether fast or slow, is prodigious; any marked

improvement in the contour of screws will mean either a saving of fuel

or an increase of speed. Of equal importance with water-propulsion is

the setting in motion of air. In blast furnaces enormous volumes of air

are forced at high pressure into the fuel and ore: the fans are

carefully molded in screw form, any departure from the best curves

entailing serious loss. Fans for less important services are seldom

shaped with care and usually waste much energy.

Turbines.

Allied to screws are turbine wheels, much the most efficient of water

motors. The shaping of their vanes as volutes minimizes the loss of

energy in shock as the water comes in, and lessens to the utmost the

velocity of the stream as it leaves the wheel. Now that steam turbines

are scoring a success both on land and sea the contouring of their vanes

with extreme nicety is an important problem of the engineer. A perfected

form means the highest economy.

[Illustration: Curves of turbines.

Niagara Power Co.]

It is interesting to note how the screw propeller, the fan, and the

turbine wheel have each led to a converse invention. Mr. Edwin Reynolds,

of Milwaukee, has devised a pump in screw form of capital efficiency

under low heads. The fan has long had its converse in the windmill, now

more popular throughout America than ever before, mainly because shaped

with new excellence. In the best models, built of steel, the sails are

each a section of a volute carefully designed to discharge the wind

evenly, just as in the parallel case of emission from a water mover,

such as the Worthington pump. This capital pump is simply a turbine

wheel reversed. Its impeller and diffusion vanes take up water from

rest, lift it to a height which may be as much as 2,000 feet, and then

deliver it at rest, with little loss from internal eddies or slippage.

[Illustration: Steel vanes of wind-mill.

Fairbanks, Morse & Co., Chicago.]

The Pelton wheel, pre-eminent among water-motors of the impulse type,

owes its economy chiefly to each bucket being divided in halves and

curved with the utmost nicety.

[Illustration: Pelton water wheel.]

[Illustration: Jet for Pelton wheel.]

CHAPTER VII

FORM--_Continued_. LIGHT ECONOMIZED BY RIGHTLY SHAPED GLASS. HEAT SAVED

BY WELL DESIGNED CONVEYORS AND RADIATORS

Why rough glass may be better than smooth . . . Light is directed in

useful paths by prisms . . . The magic of total reflection is turned

to account . . . Holophane globes . . . Prisms in binocular glasses

. . . Lens grinding . . . Radiation of heat promoted or prevented at

will.

A Shrewd Observer Improves Windows.

These are times when an inheritance, such as the window pane, venerable

though it be, is freely criticized and shown to be far from perfect. We

find, indeed, that surfaces and forms long given to the glass through

which light passes, or from which light is reflected, are faulty and

wasteful. This means that sunshine can be turned to better account than

ever before, that artificial light can be employed with an economy

wholly new. A few years ago when we provided a window with plate glass,

smooth enough for a mirror, nothing better seemed possible. Thanks to

the late Edward Atkinson, of Boston, we know to-day that in many cases

glass may be too smooth to give us the best service, that often we may

get much more light from panes of rough, cheap make than from costly

plate glass. He tells us: “In 1883, when I inspected a large number of

English cotton mills, I found them glazed with rough glass of rather

poor quality, the common glass of England being inferior to our own from

the general lack of good sand. On asking why rough glass was used

instead of smooth I was told that rough glass gave a uniform and better

light. To my astonishment I found this true. The interior of a mill so

lighted had the aspect of diffused illumination. This led me to reason

on the subject. I looked into the construction of the Fresnel lens, in

which a combination of lenses and curved surfaces concentrates rays of

light into a single far reaching beam. I reasoned that if one set of

angles or curves could thus concentrate light, then by reversal of such

angles or surfaces, light could be diffused.”

Mr. Atkinson proceeded to gather specimens of glass not only of common

rough surface, but also in ribbed and prismatic forms. These he handed

for examination and comparison to Professor Charles L. Norton of the

Massachusetts Institute of Technology, Boston. His report says: “The

hopelessness of trying to get something for nothing, that is, to get a

sheet of window glass to throw into a room more light than fell upon it,

appeared so plain to me that I made all my preparations to measure not a

gain but a loss of light in using Mr. Atkinson’s samples. The results of

the tests may be briefly stated: In a room thirty feet or more deep we

may increase the light to from three to fifteen times its present effect

by using ‘Factory Ribbed’ glass instead of plane glass in the upper

sash. By using prisms we may, under certain conditions, increase the

effective light to fifty times its present strength. The gain in

effective light on substituting ribbed glass or prisms for plane glass

is much greater when the sky-angle is small, as in the case of windows

opening upon light shafts or narrow alleys. With the use of prisms a

desk fifty feet from a window has been better lighted than when but

twenty feet from the same window fitted with plane glass. . . . ‘Ribbed’

and ‘Maze’ glass are of very great value in softening the light,

especially when windows are directly exposed to the sun, aside from

their effectiveness in strengthening the light at distant points. With

the ‘Maze’ glass the artist may have, in all weathers and in all

directions, what is in effect a much-desired north light. The same glass

provides the photographer with light as well diffused as when cloth

screens or shades are employed and of much greater intensity.”

Plate prism glass is now manufactured with its outer or street surface

ground and polished like plate glass, with its prisms accurate and

smooth. In dimensions which may reach fifty-four by sixty inches it

affords surfaces easily kept clean, and transmitting much more light

than glass held in frames of small divisions.

Whence the gain in thus exchanging plane glass for glass rough, ribbed,

or prismatic? Rays streaming through an ordinary window strike nearby

surfaces of wall, ceiling, and floor; from these they are reflected in

large measure and return through the glass to outer space. Rough,

ribbed, or prismatic glass throws the rays much further into the room,

hence they strike so much larger an area of wall, ceiling, and floor

that in being reflected again and again the light is well diffused, and

but little is sent forth again into outside space. The form of the glass

gives the entering light its most useful direction, so that the new

panes serve better than the old. This effect is most striking when

prisms are carefully adapted to a particular case in both their angles

and their placing. In traversing glass, light is absorbed and wasted, so

that the shorter its path the better. In the compound lens devised in

1822 for lighthouses by Augustin Jean Fresnel, light is as effectively

bent by the part of the glass shown in dark lines as if the whole lens

were employed.

[Illustration: Luxfer prism.]

[Illustration: Fresnel lens.]

This brings us to means for the best use of artificial light. Within the

past thirty years the standard of illumination, thanks to electricity,

has steadily risen. More important than ever, therefore, is it that

light should be employed pleasantly and effectively. This in the main is

a question of placing the sources of light judiciously, and of so

reflecting and refracting their rays that they will be of agreeable

quality, and arrive where they are wanted with the least possible loss.

Reflectors rightly shaped and kept clean economize much light. For lack

of them in streets and squares we may sometimes observe half the rays

from a lamp taking their way to the sky where they do no good. In shop

windows ribbed reflectors throw full illumination on the wares

displayed, while the sources of light are out of view. The same method

is employed in art galleries and in museums. A parabolic reflector sends

forth as parallel rays the powerful beam of a lighthouse, a locomotive,

or a searchlight. An incandescent lamp of ingenious design is silvered

on its upper half so that none of its light is wasted. Because the arc

lamp is the cheapest of all illuminants it is adopted for out-of-door

lighting where its unpleasant glare is tempered by distance. In factory

lighting its brightness is excessive and harmful unless moderated. A

capital plan is to employ an ordinary continuous current and place the

positive carbon, with its brilliant centre, below the negative carbon;

beneath these two carbons a good reflector throws the rays to the

ceiling, whence they descend with agreeable diffusion and much less loss

than when globes of ground glass surround the arc. A common white

ceiling when quite flat is an excellent reflector; indeed, a sheet of

white blotting paper returns light nearly as well as a polished mirror,

and for many purposes it serves better; the mirror sends back its beam

in a sharply defined area which may be dazzling, the paper scatters

light with thorough and agreeable effect.

[Illustration: Lamp and reflector a unit.]

[Illustration: Inverted arc-light.]

Usually a mirror is a sheet of highly polished metal, or a plate of

glass with a quicksilver backing; preferable to either is clear glass,

all by itself, so formed as totally to reflect an impinging beam of

light. To understand the principle involved in its use we will for a

little while bid good-by to lamps of all kinds.

Delight and Gain as We Watch a Fish in Water.

A hall of delights is the New York Aquarium, in the historic Castle

Garden at the Battery. Its tanks display a varied and superb collection

of fish, whose beauty of form and color heightened by swift and graceful

motion, fascinates the eye as no museum of dead things, however

splendid, ever does. When a tank is still, or nearly still, and a

gold-fish or a perch is quietly resting near the surface of the water,

one may see its form reflected from that surface as perfectly as if by a

mirror. The point of view must be close to the tank, with the eye

somewhat lower than the fish. So perfect, at times, is this mirroring

that young folks are apt to suppose the reflection to be a second fish,

and they are puzzled to remark how strangely it resembles its mate just

below. What explains this reflection? A ray of light can always pass

from a rare medium, such as air, into a dense medium, such as water,

because it is bent toward their common perpendicular. But a ray cannot

always pass from a dense into a rare medium, from, let us say, water

into air, for if the ray were to be bent away from the common

perpendicular more than 90° it would altogether fail to emerge from the

water. No luminous ray can pass from water into air if it makes a

greater angle with the perpendicular than 48° 35´. Suppose AB (page 78)

to be the water level of a tank. A ray leaving F will be bent so as to

reach C, a ray from G will reach D, a ray from H will reach E; but a ray

from L will be bent so much as to pass along the surface of the water as

OB, and a ray from I will be bent so as to return beneath the surface of

the water to I. Rays such as I, undergoing total reflection, afford us

our second image of a fish at rest near the surface of water: to observe

this kind of image we need not journey to the New York Aquarium; with

patience we may behold it in a small home aquarium with flat sides of

clear glass, waiting until the water is quiet and a fish comes close to

the surface.

[Illustration: Sacramento perch totally reflected in aquarium.

A, surface of water.]

Every dense transparent substance has this ability to yield images by

total reflection, each substance having a critical angle of its own; we

have just seen that for water this angle is 48° 35´. Glass is made in

many varieties, each with a special critical angle, never much different

from that of water. A right-angled prism of glass, which any optician

can supply, serves as a capital mirror for rays striking its surface at

ninety degrees. Such prisms are employed in opera glasses, in hand

telescopes, in reflectors for light-houses, and in the Holophane globes

we are about to examine. The efficiency of these prisms may be as much

as 92 per cent., whereas that of the best silvered mirrors never exceeds

90 per cent. The loss in a prism is due to a slight reflection by the

surface on which the rays first fall, and by the absorption of light in

the glass itself; this second loss, of course, increases with the

thickness of the prism.

[Illustration: AB water level. F, G, H, L are refracted to C, D, E, B. I

is totally reflected to I.]

[Illustration: Holophane globe, vertical section.]

[Illustration: Section of Holophane globe.

Ray A is refracted as A´, C as C´. B, totally reflected, then refracted,

emerges as B´. D takes a similar course, emerging as D´.]

Total Reflection in Artificial Lighting: Holophane Globes.

Now that we understand the principle of total reflection, let us see how

it is applied to increasing the effectiveness of a Welsbach mantle or an

electric lamp. And first let us say that we may wish light upon a small

area, mainly in a single direction, as downward upon a desk or

reading-chair. Or, in a quite different manner, if we are to illuminate

a wide space such as that of a large parlor. These requirements are

fulfilled by the Holophane globes, devised by M. Blondel and M.

Psaroudaki, which are made in many shapes, each adapted to a specific

duty. The upper half of each globe is formed into prisms of such angles

that, zone by zone, the glass totally reflects impinging rays in just

the directions desired. The contouring is accurate to the thousandth

part of an inch. With this thorough reflection is combined diffusion as

thorough, the interior of the globe being shaped as ribs. Thus, with the

least possible waste, the upper half of the source of light is utilized.

What of the lower half? Its rays pass through prisms formed so as to

refract impinging light into desired paths with but little loss. As a

whole, therefore, these globes furnish a beautiful means of illumination

with all but perfect economy, special forms of them sending light in any

direction desired.

[Illustration: Diffusing curves.

Holophane globe. Rays are split into b, e, reflected, then as e, f, g,

refracted; and into b, c, d, refracted.]

[Illustration: Class A, Holophane globe, throwing rays mainly downward.

Class B, rays mainly directed at an angle of 60°.

Class C, casting rays chiefly in a lateral direction.]

[Illustration: Section of Holophane globe and Welsbach mantle, showing

distribution of light.

Each typical ray as refracted is marked by a letter of its own.]

[Illustration: How a wire may be shortened while its original direction

is resumed.]

Total Reflection in Binocular Glasses.

In the Zeiss Works at Jena, in Germany, optical instruments of the

highest excellence are manufactured; many of these take advantage of the

principle of total reflection we have been considering. When the task

was assumed of producing a new and improved telescope, it was observed

that an ordinary telescope, built up of lenses, is inconveniently long

and heavy in comparison with its magnifying power. The question arose

whether it was possible to construct short instruments of a magnifying

power of four to twelve diameters. Porro, an Italian, about the middle

of the nineteenth century suggested totally reflecting prisms so placed

that while the total travel of a ray would be the same as in an ordinary

telescope, the two ends of the luminous path would be near together,

while the whole would be more effective than if four mirrors were

employed. His idea may be represented by a wire one meter long so bent

that its ends are much less than one meter apart. In an illustration of

a field-glass as manufactured at the Zeiss Works, on the Porro

principle, it will be remarked that the entering ray passes through

lenses which are farther apart than the lenses which form the

eye-pieces. Thus a much wider field is viewed than that of an ordinary

glass, while as the two images received from the two eye-pieces differ

more than those observed in direct vision, the perception of depth is

increased in a notable degree. This construction is adapted to sporting,

marine, and opera-glasses, as well as to field-glasses.

[Illustration: Four mirrors, 1, 2, 3, 4, reflect a ray in a line

parallel to its original path.]

[Illustration: Prisms for Zeiss binocular glasses.]

Lenses Still Much Used.

Lenses nevertheless continue to be much more important than prisms, and

the proper shaping of their surfaces involves high reaches of both

science and art. The properties of the glass, of course, count for most

in producing combinations free from color for telescopes, microscopes,

and cameras. Jena glass, described in another chapter of this book, with

its extraordinary range of refractive and dispersive qualities has

brought optical instruments to virtual perfection. Meanwhile the arts

of lens-grinding leave little to be expected in the way of future

improvement. It is astonishing that a lens forty-two inches wide can be

so truly curved as to focus the image of a star as an immeasurable dot.

[Illustration: Zeiss binocular glasses: longitudinal and

cross-sections.]

The Production of Optical Surfaces.

Let us look at some of the instruments designed by a master for shaping

glass discs into lenses. Some of the best telescopes in existence are

from the hands of Mr. John A. Brashear, of Allegheny, Pennsylvania. The

grinding tools he employs he has contoured in such wise as to produce

desired curves free from error. The first polishers are of the ordinary

form with square or circular facets equally distributed over the surface

of the tool, as in Figs. H and 8. When the polish is brought to its

best, the glass is allowed to cool slowly to a normal temperature, and

is then carefully studied as to its defects. These are removed and the

surfaces finished with iron tools, of the same diameter as the surface

to be worked, each tool being laid off into six sections, as in Figs.

3, 4, 5, 6, 7. The tool being warmed, pitch is spread over its leaf-like

spaces, which are given the proper curve by being pressed down on the

previously wetted concave surface; the pitch and tool are next quickly

cooled with water. In the shaping of these spaces rests success. The

zone, a, a, in the first figure, needing the greatest amount of

abrasion, meets the widest part of the leaflet, but in order that no

zonal error may be introduced, as in b, c, c, b, of the second figure,

it is gently tapered in each direction, the amount of taper being

governed by the lateral stroke given to the polisher, as well as by the

amount of departure of the zone from the normal curve.

[Illustration: Tools for producing optical surfaces.

John A. Brashear, Allegheny, Pa.]

But after all the astronomers aided by lenses thus carefully shaped are

few, while millions of people suffer from defects of sight which are

overcome by suitably formed spectacles.

Bi-focal Spectacles.

In this field a recent minor improvement is worthy of mention. Benjamin

Franklin many years ago made a pair of spectacles in which the upper

half of each glass was ground for far seeing, the lower half for near

seeing. To-day such bi-focal spectacles are not made in halves, with an

unpleasant broken line across them. In each of the new eyeglasses toward

the base a small lens of dense quality is enclosed; through this lens a

wearer looks at objects nearby; through the upper part of the eyeglass

he looks at distant objects. The joining of the three parts is effected

so skilfully as not to be discernible.

[Illustration: Bi-focal lens for spectacles.]

Economy of Heat.

From light we pass to its twin phase of energy, heat, for a glance at

the forms of devices which enable us to use heat with economy. When we

wish a furnace, crucible, or cooking vessel to maintain the highest

possible temperature, we give it as little surface as possible. On the

contrary when a warming apparatus is devised, its surface is freely

extended. The traditional fireplace, for all its cheerfulness, yields

but little heat. Benjamin Franklin copied its form in the stove which

bears his name; as it stands out from a wall it warms the air all around

itself, instead of on one side only. This model is familiar in gas

stoves, whose heat thoroughly radiated and convected far exceeds that

derived from fireplaces. In Canada forty years ago it was usual,

especially in the country, to set up gallows-pipes and dumb-stoves, or

drums, bulky, hollow structures of sheet iron, which obliged the heated

products of combustion to take a roundabout course as they passed to the

chimney. To be sure as thus cooled the gases were less effective as

draft makers, but we must remember that one of the most wasteful uses of

fire is in warming air or other gases for the sake of putting them in

motion. In modern factories, central lighting stations, and the like

huge installations, mechanical draft sends a quick current through a

short chimney, saving much fuel. Excellent in design are the tile stoves

of Germany and Holland. Their gentle heat does not parch the air; in

moderately cold weather they render it unnecessary to light furnaces

which develop, at such times, unduly high temperatures.

[Illustration: Canadian box stove with gallows-pipe.]

In factories the heating coils filled with steam or hot water were at

first fastened to the floor. Then came attaching them to the ceiling

whence their heat is gently radiated; on the floor the coils may gather

dust and dirt with risk of fire; with the other plan there is a saving

of floor space, and accidental leaks are at once in evidence.

[Illustration: Canadian dumb-stove.]

Tubes for warming are specially effective when dented or buckled in

directions at right angles to each other and to the axis of the tube.

This form gives the heating water or steam a swirling motion which

causes it to part more rapidly with its heat than does a cylindrical

tube of the same surface. Gold’s electric heater for street-cars,

bath-rooms, and the like, is a spiral of resistant alloy, hung in a

light metallic frame, the whole presenting a large surface to the air.

Automobiles driven by heat engines require coils of the utmost possible

surface whereat cooling can take place; in many cases this cooling is

furthered by the action of a quick fan. In like manner the condensers of

steam-engines, especially aboard ship, are made up of slender tubes

presenting to the steam a chilling area of vast extent.

[Illustration: Tubing for radiator.

Dalham Works, Manchester, England.]

[Illustration: Gold’s electric heater.]

[Illustration: Stolp wired tube for automobiles.]

Inventors have long addressed themselves to the difficulty caused by the

expansion and contraction of structures as temperatures change. For

years the cylindrical fire-boxes of marine boilers have been corrugated,

so as to allow them a certain play without breaking from their

fastenings, or tearing their seams, when heated or cooled. This form is

adopted with success for the Morison fire-boxes of the Vanderbilt

locomotives. In quite different situations metal piping, in a length of

let us say 100 feet, is provided against trouble from shrinkage or

expansion by a U bend. When the diameter of the pipe is twelve inches,

this bend is usually about ten feet in extent; for a six inch pipe, a

bend six feet long suffices. Another difficulty due to heat is the

limitation of speed imposed by the heat which friction creates. A new

type of circular saw has a hollow arbor through which flows cold water,

so that motion may be faster than ever before. The same arbor appears in

various other machines with like advantage.

[Illustration: Corrugated boiler.]

[Illustration: Pipe so bent as to permit contraction or expansion.]

CHAPTER VIII

FORM--_Continued_. TOOLS AND IMPLEMENTS SHAPED FOR EFFICIENCY

Edge tools old and new . . . Cutting a ring is easier than cutting

away a whole circle . . . Lathes, planers, shapers, and milling

machines far outspeed the hand . . . Abrasive wheels and presses

supersede old appliances . . . Use creates beauty . . . Convenience

in use . . . Ingenuity may be spurred by poverty in resources.

Tools and Implements.

We have just reviewed, all too briefly, how light and heat are

economized by structures of judicious form. At this point we will bestow

a rapid glance at the economy of work as promoted by sound design in

tools and implements, in the machines which embody these for tasks far

beyond the personal skill or power of the strongest and deftest

mechanic.

When of old a savage took up a stone to serve as a rude knife or chisel,

we may be sure that he chose the sharpest flint he could find. If he

could better its shape by knocking it into something like a wedge, what

task was easier? Our museums display an immense variety of stone

hammers, axes, knives, and arrowheads, showing how art long ago improved

the forms of simple tools and weapons offered by nature. Modern tools

and weapons, for all their immense diversity, were every one prefigured

in the rude armory of primitive man.

Descended from his flint knife is the abounding variety of steel cutting

tools all the way from the razor, concave on both sides, to the axe,

doubly convex. As the arts have become more specialized, as artificial

power has been introduced, the contrasts of the form of one tool with

another have grown more and more striking. The bar which slices metal is

stout of build, and rectangular in section, while a lancet is little

wider or thicker than a blade of grass. The knives which divide

leather, rubber, and rope, differ much from one another; the knife which

separates the leaves of a book serves best when dull. Gouges for carving

are nicely adapted to the profiles they are to cut; while the exigencies

of the power-lathe require its tools to be designed of particular

strength and rigidity. Among revolving hand-tools the brace is the most

important, enabling the workman to exert great leverage. A minor tool,

the gimlet, was formerly more in use than to-day. Now that screws are

made with gimlet points they break their own paths.

[Illustration: Carving chisels and gouges.]

[Illustration: Lathe cutters.]

[Illustration: Ratchet bit brace.]

From the beginning tool-makers have shown skill in fitting a tool to the

hand, as in the Eskimo skin-scraper; this simple adaptation may have

arrived in copying the effect of wear. Other good hints have come from

observing an implement after its work is done. At the places where mud

clung to a plowshare the plow-maker was long ago told at what points to

raise his metal; conversely, when a cutter of any kind is unduly worn at

any part of its side, there the metal asks to be somewhat narrowed down.

[Illustration: Eskimo skin scraper.]

[Illustration: Double tool drill cutting boiler plate.]

[Illustration: A common drill removes a whole circle of stone.]

[Illustration: A ring drill removes much less stone with the same

effect.]

Annular Drills.

A circle of say two feet in diameter, may be readily cut from a boiler

plate by two cutters, one at each end of a horizontal bar, the bar being

supported by a central upright axis receiving the motive power. Because

the cut is narrow, but little metal is wasted as chips. A cut of this

ring-shape effects a desirable saving even when the circle to be swept

is but an inch or so in width instead of several feet. When an auger

takes its way through a plank it removes as chips all the wood within

the circle of its range; a drill, of common form, as it pierces stone or

metal acts in a similar manner. Motive power is greatly economized when

a drill is tubular, with the further advantage that within the ring cut

a solid cylinder remains to be broken off at intervals and lifted out,

its core informing to the engineer in quest of bed-rock, to the

prospector of mines or oil-fields, or to the geologist who reads at a

glance the composition of a mineral, the forces which have impressed it

age after age. Such drills, set with bortz diamonds, have accomplished

remarkable feats. In boring out 260 columns surrounding the dome of the

capitol at Springfield, Illinois, cores 22-3/4 inches in diameter were

removed from holes 24 inches wide; without sacrifice of strength there

was a saving in weight of three-fifths. At the Ellenwood coal mine,

Kingston, Pennsylvania, a core 17 feet, 5 inches in breadth was taken

from a bore only five inches wider. When the engineers in 1896 were

planning the foundations for the Williamsburg Bridge, New York, the

deepest of their 22 borings was 112 feet below high water. Steel drills

had indicated bed-rock 12 to 20 feet higher than was the actual case;

the diamond drill showed the supposed bed-rock to be merely a deposit of

boulders. No other known means could have accomplished these results. In

the same way steel guns of large calibre have been drilled so as to

leave a core of much value, while in this as in all other such tasks,

the boring demanded less energy and proved less straining than if all

the metal within the sweep of the drill had been reduced to fragments.

All these tools were prefigured in a simple ring drill used two thousand

years ago on the banks of the Nile; hollow reeds were employed, with

sand as a cutter.

[Illustration: Twist drill.]

Twist Drills.

Twist drills are superseding flat drills as stronger and better in every

way. A twist drill is made with a slight taper toward the shank end. Its

cross-section is not quite round, the diameter being reduced from a

short distance behind the cutting edge, so as to diminish friction and

give the sides of the drill as much clearance as possible. The advanced

edges of the flutes are all full circle, so as to maintain the diameter

of the drill and keep the tool steady. The advantage of the twist drill

is that its cuttings find free egress, while it always runs true,

without reforging or retempering. The cutting edges are usually ground

to an angle of sixty degrees to the center line of the drill; for brass

work the angle should be fifty degrees.

Lathe and Planer Tools.

The manner in which a lathe tool cuts metal is shown in an outline which

represents a tool feeding a cut along a piece of wrought iron. The

removed metal, in its diameter and openness, tells the expert operator

both the quality of his cutter and how it is being affected by wear. The

principal consideration, says Mr. Joshua Rose, in determining the

proper shape of a cutting tool, for use in a lathe or a planer, is where

it shall have the rake, or inclination, to make it keen enough to cut

well, and yet be as strong as possible; this is governed, in a large

degree, by the nature of the work.

[Illustration: How a tool cuts metal.

Beginning a second cut.]

[Illustration: Dacotah fire-drill.]

Machine Tools: Lathes.

In giving form to wood and metal cheaply and rapidly, machine-tools have

within recent years risen to great importance. Of these the lathe is one

of the chief. It seems to be descended from the bow drill, the tool

which was whirled by a cord wrapped round it, or it may be, that under

another sky, the lathe was derived from the potter’s wheel whose axle

was changed from a vertical to a horizontal plane. For centuries all

lathes had their cutting tools simply laid on a bar, or rest, just as in

the hand cutting lathe of to-day. While this afforded opportunity to

skill it did not lend itself to large or uniform production. Henry

Maudslay, about a century ago, immensely broadened the machine in scope

by devising the slide rest which firmly grasps the cutting tool, and

automatically moves it toward or away from the axis of the work, as

well as along the work in any desired line. This device is equally

applicable whether in turning a pencil case, the granite columns for a

cathedral, or the propeller-shaft of an ocean steamer.

[Illustration: Lathe: a, work; b, tail-stock; c, hand-tool rest; d,

dead-centre; e, live-centre; f, face-plate; g, live-spindle; h,

dead-spindle; k, head-stock; m, cone-pulley; n, driving-pulley; o, belt;

p, treadle; r, treadle-hook; s, shears; t, treadle-crank.]

[Illustration: Compound slide rest.

C, shears; E, tool carriage; H, cross slide; K, cross slide handle; L,

cross feed handle; P, tool post; T, tool; D, driver; W, work.]

[Illustration: Blanchard Lathe.

A, frame; B, carriage; C, gun stock; D, former; E, cutter-head; F, guide

wheel; G, swinging frame; H, feed motion; K, shaft for revolving stock

and former.]

The lathe has been developed in many ways until it has become one of the

most complex of all machines, adapted to tasks which even twenty years

ago seemed impossible. Only two of its varieties can here be noticed,

the Blanchard lathe for cutting irregular forms, and the turret lathe.

An illustration, taken from an old engraving shows the Blanchard lathe

as originally built for shoe-lasts. A pattern-last and the block to be

carved are fixed on the same axis and are revolved by a pulley. On a

sliding carriage are fastened pivots from which are freely suspended the

axles of a cutting wheel, and a friction wheel, equal in diameter. The

cutting wheel turns on a horizontal axle, and bears on its periphery a

series of cutters. The friction wheel is in contact with the

pattern-last and presses against it while in motion. During revolution,

the pattern, irregular in its surface, causes the axis to approach or

recede from this friction wheel; the cutting wheel in its corresponding

motion removes wood from the block until a duplicate of the pattern

appears. This lathe much improved and modified now turns not only

gun-stocks, axe-handles and the like, but repeats elaborate carvings

with precision. Ornaments for Pullman cars are produced by this machine.

[Illustration: Turret lathe: an early Brown & Sharpe model.

C, carriage; T, turret; L, hand lever; F, face plate; D, jaw chuck; E,

tool.]

[Illustration: Turret of turret lathe. Side view. Top view.]

The turret lathe, equally ingenious, has a turret or capstan, which

carries let us say eight different tools, one on each of its eight

faces. In its turn each tool operates on the work in its forward

traverse; it then retires while the turret automatically moves through

one-eighth of a circle, when the next tool emerges for its task, and so

on.[7]

[7] The turret principle is embodied in drills and a variety of

other machines. It was adopted in remarkable fashion by John

Ericsson in his Monitor, launched in 1862 for service in the Civil

War. Because this vessel had to navigate shallow streams, its draft

was limited to eleven feet. As it was thus impossible to carry the

burden of armor necessary to protect a high-sided vessel, he was

obliged to design a sunken hull. Guns and gunner were protected

within a covered cylindrical turret which as it turned on its

vertical axis, delivered an all-round fire while the Monitor stood

still. Ericsson’s original turret, and its later modifications in

the leading navies of the world, are described in the Life of John

Ericsson, by William Conant Church, New York, Scribner, 1890.

[Illustration: Ericsson’s Monitor.]

Lathes have given rise to planers, now built of great strength and

in highly complicated designs. In a lathe the object turns upon

centers against a tool; a planer carries its tool in a revolving

cylinder, the work being fed in a straight line. A shaper, with much

the same essential construction, moves along its work, the wood or

metal operated on remaining stationary. With a planer or a shaper

the size and uniformity of the work depend upon the skill of the

operator. The planer has led to the invention of a machine which

dispenses with this skill. Bramah, in 1811, employed a revolving

cutter to plane iron, adapting to metal the familiar mechanism for

planing wood. This was the beginning of the milling machine, now so

remarkably developed and improved. A skilled mechanic sets the

machine and the chucks which hold the work; an unskilled hand can

continue the operations, his products being uniformly of the

dimensions and forms desired. Intricate shapes are easily executed,

quite impracticable on any other machine. At first the revolving

mechanism and its cutters were a single piece of metal; to-day

cutters of costly quality are inserted in cheap metal; these

inserted cutters when worn out are easily replaced.

[Illustration: Iron planer; a, b, c, d, fixed cutting tools; M, moving

bed.

Niles-Bement-Pond Co., New York.]

[Illustration: Iron shaper: a, b, fixed cutting tools. K, M, traveling

bars.

Niles-Bement-Pond Co., New York.]

[Illustration: Milling machine, R. K. Le Blond Machine Tool Co.,

Cincinnati.

A, table; B, overhanging arm; C, cutters; D, spindle; E, feed box.]

In many cases the milling machine ousts the planer as much more

economical. At the shops of the Taylor Signal Company, Buffalo, a miller

of the Cincinnati Milling Machine Company does nine-fold as much work as

a planer. It takes a first cut 1/8 inch deep across a full width of 12

inches, makes 60 revolutions per minute, feeds .075 inch per turn,

giving a table travel of 4-1/2 inches per minute, with an accuracy limit

of .001 inch.

[Illustration: Milling cutters with inserted teeth.

Cincinnati Milling Machine Co.]

Now for a glimpse of what a great inventor had to suffer because he

lived prior to the era of machine tools, before the days, indeed, of

that indispensable organ of the lathe, its slide rest. The first steam

engines of James Watt built at the Soho Works, near Birmingham, are thus

described:--“A cast iron cylinder, over 18 inches in diameter, an inch

thick and weighing half a ton, not perfect, but without any gross error

was procured, and the piston, to diminish friction and the consequent

wear of metal, was girt with a brass hoop two inches broad. When first

tried the engine goes marvelously bad; it made eight strokes per minute;

but upon Joseph’s endeavoring to mend it, it stood still; and that, too,

though the piston was helped with all the appliances of hat, papier

maché, grease, blacklead powder, a bottle of oil to drain through the

hat and lubricate the sides, and an iron weight above all to prevent the

piston leaving the paper behind in its stroke--after some imperfections

of the valves were remedied, the engine makes 500 strokes with about two

hundred weight of coals.” In another month or two, with better

condensation, it “makes 2,000 strokes with one hundred weight of coals.”

[Illustration: Milling cutters executing complex curves.

Brown & Sharpe, Providence, R. I.]

Emery and Carborundum Wheels.

Emery, carborundum and alundum wheels are developed from the grindstone

of the distant past. That stone gives a straight-line finish or edge to

the surfaces submitted to it; and as the work is shifted in front of the

stone these surfaces may take a curved or other contour. But a

grindstone, let it be as hard as can be found, is not hard enough to

take and keep any other than a cylindrical form. Its successors of

to-day, the carborundum wheel especially, can be of varied shapes, and

transfer these to metal with celerity and economy.

Carborundum, a compound of silicon and carbon, is produced at Niagara

Falls, New York, by a process devised by Mr. E. G. Acheson. In an

electrical furnace are placed granulated coke, sand, a little salt, and

some sawdust to keep the mixture porous and allow generated gases to

escape freely. The crystals of carborundum thus produced require seven

horse-power hours for each pound; in hardness they are excelled by the

diamond only. United under severe hydraulic pressure by a vitrified

bond they are eight times as efficient as emery in abrasion. Carborundum

wheels are replacing lathes as a means of finishing axles, piston-rods

and rolls; their accuracy is unsurpassed, while they demand but one

third the time needed by a steel tool.

[Illustration: Emery wheels.]

[Illustration: Carborundum Co., Niagara Falls, N. Y.

Carborundum wheel edges.]

Form in Plastic Arts.

At the very dawn of art moist clay was molded into useful plates and

bowls. This foreran not only all that the potter has since accomplished,

but all that has been achieved in the foundry and the mint. In making

bricks, tiles, and terra cotta, the first task is to make the clay

plastic, then advantage is taken of its plasticity. In like manner we

heat a metal to fluidity, and then pour it into a mold to make a fence

rail, a stove plate, or a car wheel. An electric bath refines upon this

process. Copper, let us say, dissolves in a tank, and concurrently its

particles are deposited on a mold from which the metal can be readily

stripped, avoiding the distortion inevitable when heat has come into

play.

Within the past ten years concrete has grown into much importance as a

building material, especially as reinforced with steel. It is a great

deal easier and cheaper to pour a wall into molds than to lay courses of

brick, or cut and dispose stone-work. Elsewhere in this book a few pages

are given to reinforced concrete, and its applications.

Pressing and Stamping.

Pressing, like molding, has of late years much extended its range of

forms. In germ it goes back to the distant day when seals were impressed

upon clay tablets, and coins or medals were struck from hard matrices.

In glass manufacture the press has been used for centuries. Cheap

pressed tumblers and bowls have long been accompanied by cheap metal

pots and pans, plates and basins, stamped by machinery. To-day much

enlarged and improved, such machinery, as a Bliss press, makes a kitchen

sink from a sheet of steel, forms gears and pinions from round bars of

metal, and executes the intricate curves of a mandolin in a plate of

aluminum. For a good while the spinning lathe gave us from thin metallic

sheets a variety of cups, saucers, dishes, parts of kettles, lamps, and

the like. To-day each of these articles is produced by a single blow of

a die, proving that metals are plastic in a degree unsuspected in former

days. Thus it comes about that the seams necessary to the tinman and the

coppersmith, with all their liability to leaks and uncleanliness, have

been largely dismissed and may soon be wholly banished. Pressing is

illustrated on pages 184 to 186 of this book.

Old and New Means of Conferring Form.

To-day we are rich in old and new facilities for the bestowal of form.

To confer shape by division we have an immense variety of knives,

scissors, saws, axes, hatchets and shears. These, together with hammers,

chisels and gouges enable us to disengage from a mass not merely a

simple rail, panel, or table-top, but a carving or a statue. Surfaces

are smoothed with a rasp, a file, a plane; sand is rubbed on abrasively,

or falls from a height, or is forcibly blown with a blast of steam or

air. Emery either spread on paper, or glued upon a wheel, grinds with an

accuracy and speed new to art; and all that emery can do is outdone by

carborundum and alundum, which slice away metal as if chalk, be its

hardness what it may. Perforation is accomplished with rotary drills, or

by a sandblast, or on occasion by corrosive acids--a final resource in

treating refractory stone. Rolls of tremendous power reduce iron and

steel in thickness, and, when suitably shaped, confer form on railroad

rails, girders and the like. Every tool and implement, old or new, is

now embodied in machines of gigantic force, or multiple effect, so that

the skill of an earlier generation is either not in demand at all or

passes to tasks of a delicacy never attempted before. It is by virtue of

presses, enormous in power, that to-day shapes are bestowed on metals in

successful rivalry with the ancient art of the founder himself. Indeed

the art of conferring form by pouring a liquid into molds is at this

hour largely exercised in work where heat plays no part whatever,--as in

the tasks of the builder in concrete, the labors of the electrician as

he employs a bath to separate a metal from its ore, or to plate a

surface with silver or gold.

[Illustration: Diagram of rolls to reduce steel in thickness.]

Use Creates Beauty.

In strong contrast with the varied resources of modern toil are the

simple tools and implements of prehistoric skill which, modified much or

little, are at this hour still indispensable to the mechanic, the

builder, the engineer. These simple aids early became admirable in form

so as to be all the more useful. Says Mr. George Bourne:--

“The beauty of tools is not accidental but inherent and essential. The

contours of a ship’s sail bellying in the wind are not more inevitable,

nor more graceful, than the curves of an adze-head or of a plowshare.

Cast in iron or steel, the gracefulness of a plowshare is less

destructible than the metal, yet pliant, within the limits of its type.

It changes for different soils; it is widened out or narrowed; it is

deep-grooved or shallow; not because of caprice at the foundry or to

satisfy an artistic fad, but to meet the technical demands of the expert

plowman. The most familiar example of beauty indicating subtle technique

is supplied by the admired shape of boats, which is so variable, says an

old coastguardsman, that the boat best adapted for one stretch of shore

may be dangerous if not entirely useless at another stretch ten miles

away. And as technique determines the design of a boat, or of a wagon,

or of a plowshare, so it controls absolutely the fashioning of tools,

and is responsible for any beauty or form they possess. Of all tools,

none, of course, is more exquisite than a fiddle-bow. But the fiddle-bow

never could have been perfected, because there would have been no call

for its tapering delicacy, its calculated balance of lightness and

strength, had not the violinist’s technique reached such marvelous

fineness of power. For it is the accomplished artist who is fastidious

as to his tools; the bungling beginner can bungle with anything. The

fiddle-bow, however, affords only one example of a rule which is equally

well exemplified by many humbler tools. Quarryman’s pick, coachman’s

whip, cricket-bat, fishing-rod, trowel, all have their intimate relation

to the skill of those who use them; and like animals and plants adapting

themselves each to its own place in the universal order, they attain to

beauty by force of being fit. That law of adaptation which shapes the

wings of a swallow and prescribes the poise and elegance of the branches

of trees, is the same that demands symmetry in the corn-rick and

convexity in the barrel; and that, exerting itself with matchless

precision through the trained senses of haymakers and woodmen, gives the

final curve to the handles of their scythes and the shafts of their

axes. Hence the beauty of a tool is an unfailing sign that in the

proper handling of it technique is present.”[8]

[8] Cornhill Magazine, London, September, 1903.

In the course of a judicious review of the mechanical engineering of

machine tools, Mr. Charles Griffin has this to say regarding

convenience:--[9]

[9] Engineering Magazine, New York, May, 1901.

Convenience in the Use of Machines.

“A tool is an investment, the interest which it earns depending on the

amount of work it turns out in a given time. This depends largely on its

convenience of manipulation, involving a study of levers, handles,

wheels, knobs and other auxiliary devices, their shape and place with

reference to the best adaptation to the average human frame, the ease

and extent of their motions, and the rapidity with which these motions

may be accomplished. The position of the operator, his natural

tendencies, the motions he will go through, all have to be imagined in

view of the attainment of his maximum convenience. This study, in the

absence of any counterpart of the proposed machine, often forces a

resort to rough models, or in lieu of this, a full-size blackboard

sketch, extending to the floor, upon which the location of parts may be

tried for convenience.”

Resources Rich or Meagre as Affecting Invention.

In the National Museum, at Washington, the visitor as he inspects

examples of American aboriginal art is astonished at its union of

utility and beauty. Boat and paddle, spear and hook, basket and vase,

are as admirable in form as useful in traveling, fishing, or carrying

corn or water. How far an aboriginal designer may go largely turns upon

what variety of resources Nature offers him. No few score families on a

lonely islet of the Pacific can possibly rival the cloths and carvings

displayed by tribes ranging a Pennsylvania, or a California, abounding

with diverse minerals, plants and animals. When skill and invention

occupy so rich a land they flower into the highest creations of

aboriginal art. And yet it may be that the very fewness of a designer’s

resources but spurs him to all the more ingenuity. It depends upon who

the man is. As we look upon a collection of Eskimo harpoons and knives,

coats and kayaks, we marvel that all these should be produced with so

much excellence and variety from a scanty store of bones and teeth,

sinews and hides, with but little iron or none at all.[10]

[10] Two unrivalled books on aboriginal invention have been written

by Mr. Otis T. Mason, Curator of the Department of Ethnology at the

National Museum, Washington:--“Woman’s Share in Primitive Culture,”

New York, D. Appleton & Co., 1894; and “The Origin of Inventions,”

London, Walter Scott Publishing Co., and New York, C. Scribner’s

Sons, 1905. Both volumes are fully illustrated.

The annual reports of the Bureau of Ethnology, Smithsonian

Institution, Washington, describe and illustrate American aboriginal

art so fully and admirably as to be indispensable to the student.

CHAPTER IX

FORM--_Continued_. FORM IN ABORIGINAL ART, AS AFFECTED BY MATERIALS. OLD

FORMS PERSIST IN NEW MATERIALS

Nature’s gifts first used as given, then modified and copied . . .

Rigid materials mean stiff patterns . . . New materials have not yet

had their full effect on modern design.

Aboriginal Art.

So multiplied are the resources of modern industry that desired forms

are created at will, almost without regard to the material employed. It

is not so in primitive art, to which for a brief space we will now turn

so that our survey of form, though all too cursory, may be refreshed by

a contrast of old with new. Let us begin with a glance at some of the

aids with which man first provided himself, taking the gifts of nature

just as they were offered. In large areas of the Southern States, and of

Central America, the gourd for ages has been a common plant, and has

long served many Indian tribes as a water pitcher. On sea-shores, where

the gourd did not grow, conch-shells were used instead, their users

breaking away the outer spines and the inner whorls, leaving within a

space clean and clear. Both gourds and shells gave their forms to the

clay vessels which succeeded them.

[Illustration: Gourd-shaped vessel from Arkansas.

“Pottery of the Ancient Pueblos.”

W. H. Holmes.]

[Illustration: Gourd and derived forms. “Pottery of the Ancient

Pueblos.”

W. H. Holmes.]

[Illustration: Pomo basket. National Museum, Washington.]

In Zuni land, says Mr. F. H. Cushing, the first vessels for water were

sections of cane or tubes of wood. We may infer that the wooden tubes

were copied from the cane stems. What at first was passively accepted as

nature gave it, was afterward changed a little, and then was step by

step changed much, so that at length there grew up processes of

manufacture. There was, for example, in California a wealth of osiers,

reeds, and roots well suited for making baskets; these at last were

perfected as water-tight receptacles neither brittle like a shell nor

liable to a gourd’s swift decay. Beginning probably in mere wattling, in

the rude plaiting of mats and roofs, the weaver came gradually upon

finer and stronger materials than at first, with equal pace rising to

new delicacy of finish and beauty of design. At the National Museum in

Washington, the Hudson collection of Indian baskets from California

includes the finest specimen in the world, a Pomo basket. Its sixty

stitches to the running inch were possible only through using the carex

root, easily divided into threads at once slender and strong.[11]

[11] Many of the handsomest baskets at the National Museum, as well

as baskets from other great collections, are illustrated, partly in

color, in “Indian Basketry,” by Otis T. Mason, curator of the

ethnological department of the National Museum. The publishers are

Doubleday, Page & Co., New York.

[Illustration: Bilhoola basket of woven cedar bast. “Basket work of

North American Aborigines.” Otis T. Mason.]

It is interesting to observe the limitation imposed upon a primitive

designer by the qualities of the leaf, shell, or cane in his hands, the

way in which these qualities point him to the forms in which he may

excel. Of this we have capital examples in the basket-work of the North

American aborigines as described by Mr. Otis T. Mason, in the report of

the Smithsonian Institution, 1883-84. He says: “Along the coast of

British Columbia the great cedar (_Thuja gigantea_) grows in the

greatest abundance, and its bast furnishes a textile material of the

greatest value. Here in the use of this pliable material the savages

seem for the first time to have thought of checker-weaving. Mats,

wallets, and rectangular baskets are produced by the plainest crossing

of alternate strands varying in width from a millimeter to an inch.

Ornamentation is effected both by introducing different-colored strands

and by varying the width of the warp or the woof threads. . . . It is

not astonishing that a material so easily worked should have found its

way so extensively in the industries of this stock of Indians. Neither

should we wonder that the checker pattern in weaving should first appear

on the west coast among the only peoples possessing a material adapted

to this form of ornamentation.”

[Illustration: A square inch of the Bilhoola basket.]

Referring to the water-bottles of the Pai Utes, Mr. Mason says: “This

style can be made coarse or fine, according to the material and size of

the coil and outer threads. If two twigs of uniform thickness are

carried around, the stitch will be hatchy and open; but if one of the

twigs is larger than the other, or if yucca or other fibre replace one

of them and narrower sewing material be used, the texture will be much

finer.” Baskets and rain-hats, as woven by Haidas and many other tribes,

are waterproof when wet, owing to the closeness of their texture.

[Illustration: A free-hand scroll.

The same developed in a woven fabric.

“Form and Ornament in Ceramic Art.” W. H. Holmes.]

Idiom of Material.

When reeds or somewhat rigid fibres are woven, they compel a

straightness of edge in patterns and designs. A wave has to be suggested

by stepped or broken lines, and so we have a rectilinear meander or

fret, in contrast with its free-hand form as developed in a woven

fabric. Under the constraint of her material a squaw as she weaves a

design into a basket, must give squareness to a contour which would be

somewhat rounded were it executed in delicate threads. This is clear in

the human figures of the Pomo basket shown on page 109; and in those of

a Yokut basket bowl, also in the National Museum in Washington,

illustrated on the next page.

[Illustration: Yokut basket bowl.

“Basket Work of North American Aborigines.” Otis T. Mason.]

Stone and brick-work, in their rectilinear shapes, impose a rigidity in

architectural design from which modern bricks, in their rich variety of

flat and curved surfaces, have wrought emancipation. In the new

residential streets of St. Louis, for example, the architecture owes

much of its freedom and beauty to the new shapes in which brick is now

manufactured. Even wider liberty than now falls to the lot of the

brick-maker has always been enjoyed by the potter. In his hands clay

lends itself to any desired imitation, to any fresh design however

fanciful; what is more it invites those modifications of old forms in

which art takes its chief forward strides. All but infinite are the

variations which Japanese potters have played on the shapes of vases,

jars, kettles, and basins, each clearly true to its type, while at the

same time original in a pleasing way. How the Japanese artist in clay

has rejoiced in his freedom is exemplified in the collection of Japanese

pottery at the Museum of Fine Arts, in Boston. Says Mr. Edward S. Morse,

who brought this collection together: “Utensils for every day life,

terra cotta funeral urns, large terra cotta bowls, weights for fishing

nets, brush handles, and even clothes-hooks are in Japan made of

pottery. Where we use silver and other metals, or glass, in making

articles for daily use, the Japanese use pottery.” He adds: “The

prehistoric pottery of Japan was modeled by hand, and to-day in various

parts of the empire, this ancient art is continued in its prehistoric

form. There are many potters in Japan who are still at work using only

the hand in making bowls, delicate tea-pots, and dishes of various

kinds. The pottery vessels offered at Shinto shrines are usually made

without the use of the wheel and are unglazed. The potter’s wheel was

brought to Japan from Korea. The first was probably the kick-wheel used

in Satsuma and other southern provinces.”

The Japanese employ not only clay but wood in methods that richly repay

study. Says Mr. Ralph Adams Cram:--“In one respect Japanese architecture

is unique: it is a style developed from the exigencies of wooden

construction, and here it stands alone as the most perfect mode in wood

the world has known. As such it must be judged, and not from the narrow

canons of the West that presuppose masonry as the only building

material. . . . Perhaps the greatest lesson one learns in Japan is that

of the beauty of natural wood, and the right method of treating it. The

universal custom of the West has been to look on wood as a convenient

medium for the obtaining of ornamental form through carving and joinery,

the quality of the material itself being seldom considered. In Japan the

reverse is the case. In domestic work a Japanese builder shrinks from

anything that would draw attention from the beauty of his varied woods.

He treats them as we do precious marbles, and one is forced to confess

that under his hand wood is found to be quite as wonderful a material as

our expensive and hardly worked marbles. In Japan one comes to the

final conclusion that stains, paints, and varnish, so far as interior

work is concerned, are nothing short of artistic crimes.”[12]

[12] “Impressions of Japanese Architecture and the Allied Arts,” by

Ralph Adams Cram. New York, Baker & Taylor Co., 1905.

In strong contrast with the art of Japan is that of Egypt; on the banks

of the Nile the first buildings were of limestone, succeeded by huge

structures reared from Syene granite, with no little loss in delicacy of

ornamentation. It was only when marble, all but plastic under the

chisel, was adopted by the Greek sculptor, that the frieze of the

Parthenon could spring into life.

Here William Morris should be heard. In “Hopes and Fears for Art,” he

says: “All material offers certain difficulties to be overcome and

certain facilities to be made the most of. Up to a certain point you

must be master of your material, but you must never be so much the

master as to turn it surly, so to say. You must not make it your slave,

or presently you will be its slave also. You must master it so far as to

make it express a meaning, and to serve your aim at beauty. You may go

beyond that necessary point for your own pleasure and amusement, and

still be in the right way; but if you go on after that merely to make

people stare at your dexterity in dealing with a difficult thing, you

have forgotten art along with the rights of your material, and you will

make not a work of art, but a mere toy; you are no longer an artist, but

a juggler. The history of art gives us abundant examples and warning in

this matter. First clear, steady principle, then playing with the

danger, and lastly falling into the snare, mark with the utmost

distinctness the times of the health, the decline, and the last sickness

of art.” He illustrates this in detail from the history of mosaic in

architecture.

While the modern artist duly respects the idiom of his new materials,

their diversity and refinement, in granting him the utmost freedom,

enable him to attain a truth of execution unknown before to-day. For

writing on papyrus a brush had to be used; on vellum or paper, a pen or

pencil may also be employed, tracing lines no wider than a hair. Our

grandmothers were fond of sewing on a perforated card a motto or a

flower in silk thread; such a sampler always had an unpleasant

straightness in its outlines. When in weaving silk or linen there may

be two hundred threads to the running inch instead of ten, the designer

can introduce curves almost as flowing as if he were a painter. So too

in architecture: the log hut was perforce straight in its every line;

stone and brick made possible the arch; iron and steel are bringing in a

free choice of the best lines, whether straight or curved, all with a

new sprightliness, as witness the best of our office-buildings in New

York, such as the Whitehall, Trinity, and Empire Buildings.

[Illustration: Sampler on cardboard, executed in silk thread.]

[Illustration: Bark vessel, and derived form in clay.

“Form and Ornament in Ceramic Art.” W. H. Holmes.]

Old Forms Repeated in New Materials.

Art in its early stages seldom displays any outright invention; with all

the force of habit the savage artist clings to old familiar shapes, and

it is interesting to remark how dealing with a new material may lead or

even oblige him to modify a traditional form. The Algonquins inhabit a

country in which the birch is common. They cut and fold its bark into

vessels which, when imitated in pottery, have an unusual rectangularity.

In many Indian tribes it was customary to use as a water-holder the

paunch of a deer or a buffalo; many ancient urns of Central America have

an aperture at an upper extremity, copied from the paunch, in every case

with a simplification of outline. Winged troughs of wood were

undoubtedly in the mind of the man who made the earthen vessel

illustrated on the next page, found in an ancient grave in Arkansas. As

usual the borrower put something of himself into his work, reminding us

that the law of evolution is descent with modification. An earthen

vessel, illustrated on the next page, was plainly copied from a shell

vessel such as the specimen found not far off, in Indiana. When the

Clallam Indians, of the State of Washington, began to weave baskets,

they imitated the forms of their rude wicker fish-traps. The like

persistence was shown by the Haida squaws when taught by the

missionaries to make mats from rags; they repeated their ancient twined

model, long employed for mats and hats of vegetable fibres. As in

America, so also in Europe; when the makers of celts passed from stone

to copper or bronze, they reproduced the old forms, and only gradually

learned to economize metal, so much stronger than stone, and so much

harder to get, by narrowing and flattening their new weapons and tools.

[Illustration: Vase from tumulus. St. George, Utah.

“Pottery of the Ancient Pueblos.” W. H. Holmes.]

[Illustration: Wooden tray.

Clay derivative.

“Form and Ornament in Ceramic Art.” W. H. Holmes.]

[Illustration: Shell vessel made from a _Busycon perversum_, found at

Ritchersville, Indiana.

Earthen vessel, imitation of shell, Missouri.

From W. H. Holmes’ “Art in Shell of the Ancient Americans.”]

[Illustration: Electric lamps in candle shapes.]

Modern manufacture in its designs gives us a kindred persistence of old

forms in new things. For electric illumination we have bulbs which

recall the shape of a candle-blaze, or surmount an old-fashioned

candlestick; a gas-burner, popular for fifty years, repeats in milky

porcelain the whole length of a candle. Gas-grates, in uncounted

thousands throughout our cities every winter, offer us flames which

flicker and leap over asbestos and clay molded into the semblance of

maple or charcoal. Nor is the engineer himself, for all his sternness of

discipline, quite free from prolonging the reign of the past, even at

unwarrantable cost. When steel was first used for steam boilers there

was a period of hesitation during which the metal was used unduly thick,

as if to maintain the long familiar massiveness of iron structures. When

automobiles were invented, they at first closely resembled common

carriages. To-day, designers have departed from tradition, and provide

us with horseless vehicles which respond to their new needs in ways

wholly untrammeled by inherited ideas. In an automobile, driven by steam

or gasoline, there must be due disposition of fuel, of machinery, of

cooling apparatus, all so combined as to bring the center of gravity as

low as may be best, affording ready access to any part needing

lubrication, repair, or renewal; throughout there must be the minimum of

dead weight, of friction, and of liability to derangement; all with

means of easy, quick, and certain control. Why should these

requirements be deferred to repeating the model of a carriage drawn by a

horse? In Europe, to this hour, the railroad carriages are an imitation

of the old road-coaches, horse carriages slightly modified. America,

fortunately, from the first has had cars directly adapted to railroad

exigencies, with a thoroughfare extending the whole length of a train,

avoiding the box-like compartments which may give the lunatic or the

murderer an opportunity to work his will.

[Illustration: Notre Dame de Bonsecours, Montreal. Before restoration.]

[Illustration: NEW AMSTERDAM THEATRE, NEW YORK.

No pillars obstruct a full view of the stage.]

Sometimes an inherited form taken to a new home proves to be faulty

there, and is discarded. When Normandy sent forth its children to

Canada, they built on the shores of the St. Lawrence just such

high-pitched roofs as had sheltered them in Caen and Rouen. An example

remains at Montreal in the roof of Notre Dame de Bonsecours. But in

Montreal and Quebec the snowfall is much heavier than in Northern

France, and the Norman roofs at intervals from December to March were

wont to let loose their avalanches with an effect at times deadly.

To-day, therefore, in French Canada many of the roofs, especially in

towns and cities, are flat or nearly flat, while the best models quite

reverse the old design. In breadths somewhat concave they catch the snow

as in a basin, and allow it to melt slowly so as to run down a pipe

through the center of the building.

Under our eyes, day by day, iron and steel are taking the place of stone

and wood in architecture and engineering; yet the force of habit leads

us to continue in metal many troublesome details which were imperative

in the weak building materials of generations past. It was as recently

as the autumn of 1903 that the first large American theater was opened

having no columns to obstruct views of its stage. The architects of the

New Amsterdam Theater, New York, simply by availing themselves of the

strength of steel cantilevers have shown that henceforth all large

auditoriums may be free from obstructions to a view of the stage, pulpit

or platform. See facing page 118.

Modern architecture, in the judgment of an eminent critic, has not yet

fully responded to its new materials and methods. Says Mr. Russell

Sturgis, of New York, in “How to Judge Architecture”:--“Every important

change in building, in the past, has been accomplished by a change in

the method of design, so that even in the times of avowed revival there

was seen no attempt to stick to the old way of designing while the new

method of construction was adopted; now in the nineteenth century, and

in what we have seen of the twentieth century, our great new systems of

building have flourished and developed themselves without effect as yet

upon our methods of design. We still put a simulacrum of a stone wall

with stone window casings and pediments and cornices and great springing

arches outside of thin, light, scientifically combined, carefully

calculated metal--the appearance of a solid tower supported by a reality

of slender props and bars.”

CHAPTER X

SIZE

Heavenly bodies large and small . . . The earth as sculptured a

little at a time . . . The farmer as a divider . . . Dust and its

dangers . . . Models may mislead . . . Big structures economical

. . . Smallness of atoms . . . Advantages thereof . . . A comet may

be more repelled by the sun’s light than attracted by his mass.

Buildings, carriages, structures of all kinds, whether reared by art or

nature, often resemble one another in form while varying much in size.

Differences of dimensions are of importance to the inventor and

discoverer, and will be here briefly considered, beginning with a few of

their obvious and elementary aspects.

[Illustration: Cinders large and small on hearth.]

[Illustration: A cube as subdivided into 8 cubes of 4 times more

surface.]

Cinders Big and Little.

One frosty evening I sat with three young pupils in a room warmed by a

grate-fire. Shaking out some small live coals, I bade the boys observe

which of them turned black soonest. They were quick to see that the

smallest did, but they were unable to tell why, until I broke a large

glowing coal into a score of fragments, which almost at once turned

black. Then one of them cried, “Why, smashing that coal gave it more

surface!” This young scholar was studying the elements of astronomy that

year, so I had him give us some account of how the planets differ from

one another in size, how the moon compares with the earth in volume, and

how vastly larger than any of its worlds is the sun. Explaining to him

the fiery origin of the solar system, I shall not soon forget his

delight--in which the others presently shared--when it burst upon him

that because the moon is much smaller than the earth it must be much

cooler; that indeed, it is like a small cinder compared with a large

one. It was easy to advance from this to understanding why Jupiter, with

eleven times the diameter of the earth, still glows faintly in the sky

by its own light, and then to comprehending that the sun pours out its

wealth of heat and light because the immensity of its bulk means a

comparatively small surface to radiate from.

[Illustration: Cube built of 27 cubes of 9 times more surface.]

To make the law concerned in these examples definite and clear, I took

eight blocks, each an inch cube, and had the boys tell me how much

surface each had--six square inches. Building the eight blocks into one

cube, they then counted the square inches of its surface--twenty-four:

four times as many as those of each separate cube. With twenty-seven

blocks built into a cube, that structure was found to have a surface of

fifty-four square inches--nine times that of each component block. As

the blocks underwent the building process, a portion of their surfaces

came into contact, and thus hidden could not count in the outer surfaces

of the large cubes. The outer surfaces of these large cubes I then

painted white; when each was separated into its eight or twenty-seven

blocks, we saw in unpainted wood how surfaces were increased by this

separation into the original small cubes. Observation and comparison

brought the boys to the rule involved in these simple experiments. They

wrote: Solids of the same form vary in surface as the _square_, and in

contents as the _cube_, of their like dimensions.

This elementary law I traced that year in a variety of illustrations

presented in “A Class in Geometry,” published by A. S. Barnes & Co., New

York. Our excursions, since extended, are here given as an example of

the knitting value of a pervasive rule kept constantly in mind.

Earth Sculpture.

Our planet in diverse ways illustrates the law, just stated, of surfaces

and volumes. Forces of unresting activity quietly transform the hills

and plains, the sea coasts and lake shores of the world, and so

gradually that in many cases detection proceeds only by noting the

changes wrought in a century. For the most part these forces break up

large masses into fragments, or slowly wear away the surfaces of rocks

into dust. A lichen takes root on a granite ledge, and in a few years

reduces the rock to powder. Rain always contains a little acid, so that

in time flint itself is consumed, for all its hardness. Water soaking

through soils to form underground streams has hollowed out vast caves,

as notably in Virginia and Kentucky. Limestones and sandstones are of

open texture, and take up much moisture into their pores; in cold

weather this freezes, and in expansion wedges off thin flakes of stone.

In the North one sees the ground strewn with such splinters when the

warm April sun has melted the snow from beside a limestone fence. Watch

the rills as they descend a hillside during a rainstorm and just

afterward. They are dark with mud, and on steep declivities they carry

down pebbles and bits of broken stone, building up valleys at the

expense of high ground. Fed on a huge scale by such mud, the Mississippi

River bears in suspension to the Gulf of Mexico a little more than a

pound of solid matter in every cubic yard, a prime example of how the

waters of the globe gain upon the land. The Falls of Niagara have

retreated several miles from their original plunge; the carving of their

channel has been wrought much less by the rushing waters than by their

burden of abrading earth and sand. The ceaseless churning of water at

the foot of the Falls cuts back into the rock, undermining its upper

layers, so that ever and anon they break off from the brink of the

cataract, with the effect that the stream steadily retires.

Throughout the ocean are strong currents to be constantly surveyed and

charted on the mariner’s behalf. These currents transport fine mud, and

organisms living and dead. Corals flourish best where such currents

fetch an abundant supply of food, just as plants thrive best in rich,

loose soil. Life in the sea just like life on land is thus dependent on

forces which divide large masses into small, and distribute these small

masses over wide areas, chiefly by water carriage.

Breaking Earth for Removal or Tilth.

Inventors have taken a hint from nature as she carries a burden of mud

and pebbles in a rapid stream of water. A modern method of deepening a

water course is to reduce to fine silt the surface of its bed, and then

remove this silt with a powerful stream. Water in swift eddies both

lifts and bears away not only clay, but stone and gravel when these are

small enough. In placer-mining streams of water much more powerful are

directed against hill-slopes of earth and stone, which disappear a great

deal faster than by means of spades and shovels. One of our Northwestern

railroads runs for some miles along the base of a steep ridge, from

which at times heavy rains wash down masses of earth, sand and gravel to

the track. A powerful steam pump forcing a stream through hose removes

the obstructions from the line with amazing rapidity. Work a good deal

commoner and vastly more important consists in taking a process begun by

nature and carrying it many steps further, so as to break up masses of

earth again and again. The plow, the harrow, the sharp-toothed

cultivator, divide and subdivide the soil of farm and garden so as to

offer rootlets new surfaces at which rain may be drunk in with its

nourishing food. When a garden patch is to be fertilized by bones, these

serve best when reduced to meal, so as to be quickly and widely

absorbed.

Work of the Winds.

In earth-sculpture one of the busiest agents is the wind, especially as

it seizes ocean waves and dashes them upon beach and cliff, grinding

large stones to pieces, and reducing these at last to mere pebbles and

sand. On land the gales take hold of sand and dust with effects even

more telling: sand flung against the hardest quartz or granite will

bring it to powder at last. Sand dunes, shifting under the stress of

high winds, have spread desolation around Provincetown, Massachusetts,

and in many another region once fertile enough. This process of nature

immemorially old has been copied in modern invention, by the sandblast

devised by the late General Tilghman of Philadelphia. In its simplest

form, sand from a hopper falls in a narrow stream upon window panes,

glassware and the like, to be roughened except where protected by a

paper pattern. Had sandstone in lumps, as large as playing marbles, been

dropped on the glass, there would have been harmful fracture; as each

particle of sand weighs too little in proportion to its striking

surface to do more than detach a tiny chip, we have a bombardment wholly

useful.

Dimensions in Ignition.

Primitive man achieved an incomparable triumph when first he kindled

fire by swiftly twirling one dry stick upon another, dropping the tiny

sparks on finely divided tinder, quick to catch fire because it

presented much surface to the air. Peat, a fuel common in many parts of

the world, easily dug from bogs and marshes, can be readily dried if

chopped into fragments and exposed to the wind in open sheds. Charcoal

easily produced from wood of any kind, is often used to absorb harmful

gases in boxes of preserved meats and in household refrigerators. Its

effectiveness is due to its minute pores, presenting as they do a vast

area of capillary attraction. Charcoal, of course, burns faster when

powdered than when unbroken; and gunpowder, into which charcoal largely

enters, is molded into cakes either big, if it is to burn somewhat

slowly, or is pressed into fine grains, when an explosion all but

instantaneous is desired.

Dust Common and Uncommon.

Common dust surrounds us always, entering the tiniest chink of wall and

ceiling to show its path by a defacing mark. In dry seasons it abounds

to a distressing degree, and accumulates rapidly at considerable heights

from the ground. Observe a roof of the kind that slopes gradually toward

the street, with a trough running along the cornice to carry off the

rain or melted snow. When such a gutter is undisturbed for a few months

it is clogged with mud due to the dust which has been lifted by winds to

the roof, and swept by successive showers into the gutter. Dust

particles, because they have so much surface for their mass, are readily

caught up and borne to heights far exceeding those of the highest roofs.

The terrific explosion of the volcano at Krakatoa, in the Sunda Strait

of Java in 1883, shot more than four cubic miles of dust into the upper

levels of the atmosphere, encircling the globe with particles which fell

so slowly as for months to color the sunsets of New York and Canada, ten

thousand miles away.

Inflammable Dust.

Wheat like other grain is combustible, hence as food it sustains bodily

warmth. Under stress of necessity wheat, corn, and barley have been

burned as fuel when coal and wood have been lacking. In the process of

flour-making wheat is ground to a powder so fine that when its particles

are diffused through the air of a mill, there is a liability to

explosion because the inflammable dust comes so near to contact with the

atmospheric oxygen that at any moment they may unite. At Minneapolis,

frightful disasters were brought about in this way until specially

devised machines removed the dust. In coal mines, too, coal may fill the

air with a dust so fine that explosions take place, with serious loss of

life. In Austria it has been found that the fineness of the dust has

more to do with the violence of such explosions than has the chemical

composition of the particles.

In mining, let us observe, the whole round of work consists in

separations which bring masses from bigness to smallness, again and

again. First of all the solid walls and floors are broken up by pick, or

drill, or powder, or all together. Iron ores as hoisted to the surface

of the earth are taken to breakers which crush them into pieces suitable

for the blast furnace. When the ores carry gold, copper, lead, or tin,

this crushing is followed by stamping to facilitate the final process by

which metal is separated from worthless rock.

Dimensions in Woven Fabrics.

Spinning and weaving, remote as they are from mining, are equally

subject to the law of surfaces and volumes. It is in furthering adhesion

by giving their thread a multiplied surface that the spinner and weaver

manufacture cloth at once strong and durable. The best linens and silks

are spun in exceedingly fine threads; canvases and tweeds have threads

comparatively coarse. From the cut edge of a piece of fine silk fabric

it is hard to pull out a lengthwise thread; the task is easy with

sailcloth.

The Dimensions of Models.

From observation let us turn to experiment as we further consider the

law of size. Inventors, especially young inventors, are apt to underrate

the difficulty of supplying an old want in a new and successful way. In

their enthusiasm they may lose sight of principles which oppose their

designs, as for instance, the rules which govern the plain facts of

dimensions. Mr. James B. Eads, in planning his great bridge at St.

Louis, chose three spans instead of one span. Why? For the simple reason

that if built in one span the weight of the bridge would have been

twenty-seven times that of a span one-third as long, while only nine

times as strong, assuming that both structures had the same form. Two

pieces of rubber will clearly exhibit the contrast in question. One

piece is three feet long, one inch wide, one inch thick; the other piece

is one foot long, and measures in width and thickness one-third of an

inch. Placing each on supports at its ends we see how much more the

longer strip sags than the shorter. The longer has twenty-seven times

the mass of the other, but only nine times its strength. Many an

inventor has ignored this elementary fact and built a model of a bridge,

or roof, which has seemed excellent in the dimensions of a model, only

to prove weak and worthless when executed in full working size.

[Illustration: The upper strip of rubber is thrice as long, wide and

deep as the lower, which sags less.]

Why Big Ships are Best.

We have glanced at a few cases of invention where it has been remembered

that the larger a mass of given shape the less its surface as compared

with its bulk. Let us note how this rule enters into the tasks of the

shipbuilder. We take a narrow vial of clear glass, nearly fill it with

white oil or glycerine, cork it, and shake it smartly. Holding the vial

upright we observe that the largest bubbles of imprisoned air come first

to the top of the liquid, because in comparison with bulk they have

least surface to be resisted as they rise. For a parallel case we visit

the docks of New York, and note a wide diversity of steamers. Here is

the “Baltic,” of the White Star Line, with a length of 726 feet, and a

displacement of 28,000 tons. Less than a mile away is a small steamer

trading to Nova Scotia, having a length of but 260 feet, and a

displacement of only 1,000 tons or so. We recognize at once why the

quickest ships are always among the biggest. It is simply the case of

bubbles small and great over again; the biggest vessels in proportion to

size have least surface whereat to resist air and sea, so that they can

run fastest between port and port. As with ships, so with their engines;

economy rests with bigness; the largest engines have proportionately

least surface at which to lose heat by radiation or by contact, or for

resistance by friction as they move. Indeed in designing ocean steamers

of the greyhound type it is imperative that the utmost possible

dimensions be adopted. The “Mauretania” and the “Lusitania” just built

for the Cunard Company, to be driven by steam turbines at 25 knots an

hour, will each demand 70,000 horse-power. They are 790 feet in length

over all, 88 feet in beam, 60-1/2 feet in depth, with a displacement of

45,000 tons. Mr. William F. Durand, in his work on the resistance and

propulsion of ships, considers three vessels less huge and swift than

these Cunarders and able to cross the Atlantic in say seven days. The

5,000-ton ship could barely make the trip with no cargo at all, a

16,000-ton ship would be able to carry 3,000 tons of freight, while a

20,000-ton ship could carry 4,200 tons of cargo. Burdens of hull,

machinery, and coal do not increase as rapidly as gross tonnage when the

dimensions of a ship are enlarged.

[Illustration: Air bubbles rising in oil.]

Bigness Needs Strong Materials.

Now we begin to realize how great is the boon of cheap steel, much

stronger than iron, of which ships and engines may be built bigger than

at any earlier period. Steel of great strength has made feasible, too,

the Eiffel Tower in Paris, nearly a thousand feet tall, the

office-buildings of New York thirty stories in height, and steel will

soon cross the St. Lawrence near Quebec with a single span of 1,800

feet. In 1904, at Schenectady, N. Y., the New York Central & Hudson

River Railroad Company began comparisons between an electric locomotive

of 201,000 pounds, shown opposite page 476, and a steam locomotive so

huge that with its tender it weighed no less than 342,000 pounds. Steel,

as the material of engines and tools of all sorts enables us to build in

dimensions bolder than ever before; or, if old dimensions are not

surpassed, we are free to employ velocities quite out of the question

with iron.

It is a long time since adventurers first entrusted themselves to

floating logs, afterward tied together as rafts, and slowly improved

until they became boats moved by paddles or oars. Thus far little else

than failure has attended the inventors who have sought to navigate the

air as easily as river, lake or sea. A stride toward success was however

distinctly taken when the strongest known alloys, those of steel and

nickel, gave the aeronaut a stronger boiler, pound for pound, than he

ever had before, with wings lighter in proportion to their power than

those of earlier experiments. Let the burden of his apparatus be further

reduced, and by one-half; then we may expect him to reign in the air as

securely as the sea-gull. The original resource of the aeronaut, his

balloon, suffers from a permanent disability. Air has but 1/770 the

specific gravity of water, so that a balloon must be enormous to have

any carrying capacity worth while. And what would become of a balloon,

its rudder and ropes, if caught in a hurricane of eighty miles an hour?

A Store Continues the Lesson.

Let the aeronaut continue his wistful and envious gaze at the birds in

the sky while we turn our attention to mother earth, there to note how

every day trade surrounds us with further illustrations of the law of

size, of the gains which may attend bigness. We enter a department

store, displaying a varied stock of foods, clothing, shoes, furniture,

and so on. As we cast our eyes about its counters, shelves, and floor we

see cans of vegetables, fruit, and fish; jars of olives and vinegar;

boxes of rice, soap and crackers; paper sacks of flour and meal. Outside

the door are piled kegs, barrels, and packing cases. Plainly the cost of

paper, glass, tin, and lumber for packages must levy a large tax on

retailing. Once more is recalled our old lesson with the inch-cubes;

the bigger a jar, box, or sack, the less material it needs in proportion

to its capacity. Wholesale packers of merchandise save money as they

form packages of the largest size. The contents of each box, crate, and

sack tell the familiar story once again. The coffee is ground from the

bean that it may be readily infused in the coffee-pot; wheat is reduced

to flour, oats to fine meal, that they may be quickly cooked; sugar is

crushed that it may rapidly dissolve in the tea cup. This very task

began long ago with the mastication of food by the teeth, diminishing

the size of morsels while moistening them for digestion before they

reached the stomach.

Summer Holiday Notes.

During a visit to the country one summer, we observed new examples of

our familiar rule. When we compared the dimensions of a small sectional

cabin with those of a large house, we saw the principal reason why the

cabin was hard to keep cool in July, and hard to keep warm in December.

We noticed tasks which depended upon giving wood, cloth or other

material as much surface as possible, whether new forms were like old

ones or not. A neighboring sawmill was busy cutting up logs into thin

boards; these were piled in open tiers, so that the drying winds might

speedily finish their work. In the same way we noted a laundress

spreading out by itself each table-cloth and apron fully to catch the

wind, instead of leaving the linen as a solid heap in her basket, where

only the edges would be dried. When the farm-hands went haymaking they

followed the same rule; they tedded out their gavels to give them the

utmost supply of sun and air; when all was as dry as a bone they reared

a haycock of compact form so as to expose the least possible surface to

rain and snow.

Dimensions Molecular.

So much for things to be observed in a country ramble, in a city store,

or at the docks of a busy port. Apart from all such things is a world

unseen, standing beneath the visible world, and equally worthy of study.

Here knowledge is based upon inferences, upon what lawyers call

circumstantial evidence. The chemist by means purely indirect studies

the molecule and the atom, objects that far elude his microscope. A

molecule is a part of a compound so small that it cannot be divided

without becoming something simpler. Thus a sugar molecule is made up of

carbon, hydrogen, and oxygen atoms; were these disjoined, the sugar, as

such, would cease to be, just as a brick wall no longer exists when its

bricks and their several slices of mortar are parted from one another as

separate units. Small as molecules are they have not escaped the

measuring rod of the physicist. Some years ago Lord Kelvin

experimentally arrived at the estimate that the average molecule has a

diameter of 1/760,000,000 inch. Such molecules when compared with masses

of like form, and of a diameter of one inch; have 760,000,000 times as

much surface. In the transmission of motion, with adhesion in play,

surfaces count for much, as when a wheel in motion is brought into

contact with a wheel at rest. Here may be an explanation of why

electricity is conducted through a wire with a velocity far exceeding

any speed we can mechanically impress upon the metal, because the

molecules concerned have incomparably more surface than the wire as a

mass.

Reservoirs of Energy.

By virtue, also, of its minuteness the molecule as a reservoir of energy

can far excel a mass of visible dimensions. Let us compare two rotating

spheres, one of them of seven times the radius of the other. We spin

both at the same peripheral rate, and gradually increase this speed:

which will be the first to break apart under centrifugal strain? The

larger, and why? Because the cohesion of a sphere is in proportion to

the area of its great circle, which varies as the square of its

diameter, while centrifugal strain under swift rotation varies as the

cube of that diameter, or as the volume of the sphere. From this it

follows that we may safely spin our small sphere with a circumferential

velocity seven times that given the large sphere; therefore as

containers of energy small spheres are more effective than large, and

this inversely as their diameters. Spheres, or bodies of any other form,

if reduced in dimensions to 1/760,000,000th, would as reservoirs of

energy gain 760,000,000-fold. Thus we open a door of explanation

regarding the stupendous contrast between chemical energy and mechanical

work. Chemical processes are exerted by molecules and atoms, mechanical

work takes place among masses comparatively enormous in bulk. It may

require a hundred blows from a ponderous steam hammer to raise the

temperature of an iron bar ten degrees; that bar melts in ten seconds

when plunged into a flame produced by a few ounces of hydrogen and

oxygen gases.

Recent experiments by Professor Joseph J. Thomson point to the

probability that the atom of the chemist while a unit, is in part built

of electrons each but one-thousandth part the size of a hydrogen atom.

An electron, by virtue of its infinitesimal minuteness, becomes able to

hold proportionately much more energy than is possible to an atom moving

as a whole. This brings us to some comprehension of the astonishing

powers of radium, an element which maintains itself at a temperature 3°

to 5° Centigrade higher than that of its surroundings, probably through

the collision within each atom of its component parts.

[Illustration: Dvorak Sound-mill.]

Repulsion by Sound and Light.

Water-waves as they strike a shore or the sides of a basin exert a

thrust, or a repelling action, which may easily be observed. That

sound-waves act in similar fashion is proved by a little sound-mill

devised in 1883 by Professor V. Dvorak, of the University of Agram in

Austria. It consists of four vanes, each a small card slightly curved,

mounted on a spindle. In a sounding-box nearby is a tuning-fork which

may be struck through its stem F. A Helmholtz resonator has its wide

opening turned toward this box, its narrow opening toward the mill. A

stroke on the tuning-fork emits vibrations which send tiny jets of air

against the sails of the mill, which accordingly rotate at a pace

proportionate to the loudness of the sound.

[Illustration: A beam of light deflects dust.]

Professor Ernest F. Nichols of Columbia University, New York, and

Professor Gordon F. Hull of Dartmouth College, in the Journal of

Astrophysics, Chicago, June, 1903, describe their apparatus for

measuring the radiation pressure of light, a phenomenon analogous to

that studied by Professor Dvorak in the field of sound. In the same

number of that Journal they detail an experiment to show light exerting

a driving action on very tenuous particles. They burned a puff ball of

lycoperdon to charcoal spherules of about one-sixth the specific gravity

of water. These spherules, with some fine emery sand, they placed in a

glass tube shaped like an hour-glass; this tube was then exhausted of

its gases until a mere fraction remained which could not be removed.

With the sand and charcoal in its upper half the tube was held upright,

while a beam of light twenty to forty times as strong as sunshine was

thrown on the tube just below its neck. By tapping the glass a stream of

sand and charcoal descended; the sand fell through the beam without

deflection; the charcoal particles were driven away from the stream as

they fell through the light. Part of this effect was due to the slight

remnant of gas left in the tube which, warmed by the light, produced a

motion resembling that of a Crookes’ radiometer; the remainder of the

effect was caused by the drive or repulsion of the luminous beam. It is

argued that this repulsion by light is probably one of the causes why

the sun seems to drive away the tail of a comet, whose particles being

extremely minute have much surface and little bulk, so that they are

more repelled by the light of the sun than they are attracted by his

mass. To approach cometary conditions in an experiment it would be

necessary to intensify sunlight no less than 1,600-fold, because on the

surface of the earth its own gravitation is 1,600 times greater than

that which is there exerted by the sun.

A Law as a Binding Thread.

The law that a given shape when enlarged increases much more rapidly in

volume than in surface has, in our brief survey, bound together a wide

diversity of facts in astronomy, geology, geography, navigation,

engineering, mechanics, physics, and chemistry. A good many times I have

brought it before young folks as a means of linking together everyday

observations and principles of sweeping comprehensiveness. Boys and

girls are apt to think that there is a formidable barrier between

science and common knowledge. No such barrier exists. The sun, his

planets and their moons; the forces which carve mountains and valleys;

the arts of shipbuilders, of designers of bridges, office-buildings, and

lighthouses; the plans of the inventors of machinery; the rules

discovered by investigators who pass from appearances to the underlying

reality of molecule and atom, are all within the sway of the elementary

law we have been studying. There is a gain in thus pursuing a connecting

thread of classification, conferring order as it does on what might else

be an assemblage of things collected at random. A law such as that of

size links into unity, and fastens in the memory a vast array of

observations and experiments which otherwise would have no associating

tie, no common illumination.

CHAPTER XI

PROPERTIES

Food nourishes . . . Weapons and tools are strong and lasting . . .

Clothing adorns and protects . . . Shelter must be durable . . .

Properties modified by art . . . High utility of the bamboo . . .

Basketry finds much to use . . . Aluminium, how produced and

utilized . . . Unwelcome qualities turned to profit . . . Properties

long worthless are now gainful . . . Properties may be created at

need.

Materials are valued for their properties as well as their forms. We now

pass to a rapid survey of properties as observed in gifts of nature, as

modified by art, as turned to account in many ingenious ways, as studied

by the investigators who would fain know in what particulars of ultimate

form, size and motion, properties may really consist.

We go to market with a few different coins: one of them is worth a

hundred times as much as another of about the same size, because gold is

more beautiful than nickel, does not tarnish, may be hammered into

leaves of extreme thinness, or unites with copper as an alloy which

withstands abrasion for years after it leaves the mint. When we build a

house we wish strength in its foundation and walls, so we pay a higher

price for granite than for limestone; and choose for joists, floors and

rafters well seasoned wood in preference to newly sawn lumber liable to

warp and crack with heat in summer, with cold in winter. So with

raiment: silk is preferred to cotton or wool because handsomer,

stronger, more lasting. But food comes before shelter, raiment or any

other need of mankind, and qualities of nourishment and palatability

mark off nuts, fruits, grain and roots as suitable for food. In this

regard all living creatures exercise discrimination under penalty of

death.

Food.

A score of sparrows are flitting about a door-yard; strew a handful of

crumbs on the gravel before them; at once the birds begin picking up the

bread, leaving the gravel alone. They know crumbs, good to eat, from

stone, not good to eat. The earliest races of men, immeasurably higher

than birds in the scale of life, have eaten every herb, root, grass, and

fruit they could find. Experiment here was as wide as the world, and

bold enough in all conscience. In many cases new and delicious foods,

thoroughly wholesome, were discovered. At other times, as when the juice

of the poppy was swallowed, sleep was induced, with a hint for the

escape from pain in artificial slumber. In less happy cases the new food

was poisonous; yet even this quality was pressed into service. In

Mendocino County, California, to this day, the Indians throw soap root

and turkey mullein, both deadly, into the streams; the fish thus killed

are eaten without harm. These same Indians make acorns and buckeye horse

chestnuts into porridge and bread, pounding the seeds into a fine flour

and washing out its astringent part with water. These and other

aborigines use for food and industry many plants neglected by the white

man, taking at times guidance from the lower animals. One of the early

explorers of South Africa, Le Vaillant, says that the Hottentots and

Bushmen would eat nothing that the baboons had left alone. Following

their example he would submit to a tame baboon new plants for acceptance

or rejection as food.

Weapons and Tools.

As with food so with other resources almost as vital. Long ago the

savage learned that hickory makes good bows and arrows, that as a club

it forms a stout and lasting weapon. He discovered, too, that in these

qualities soft woods are inferior and the sumach altogether wanting.

Thus, too, with the whole round of stones from which as a warrior or a

craftsman he fashioned knives, chisels, arrowheads, axes; it was

important that only tough and durable kinds should be employed. No lump

of dry clay ever yet served as a hammer or an adze; happy were the

tribes, such as those of ancient Britain, who had at hand goodly beds

of flint from which a few well directed blows could furnish forth a

whole armory of tools and weapons.

Properties Modified.

In the eating of foods simply as found, in the use of materials for

clothing or building just as proffered by the hand of nature, much was

learned as to their qualities; some were found good, others indifferent,

still others bad. Then followed the art of modifying these qualities, so

as to bring, let us say, a fibre or a thong from stiffness to pliability

and so make it useful instead of almost worthless. The progress of man

from downright savagery may be fairly reckoned by his advances in the

power to change the qualities of foods, raiment, materials for shelter,

tools, and weapons. These arts of modification go back very far. At

first they may have consisted simply in taking advantage of the effects

of time. In the very childhood of mankind it must have been noticed that

fruit harsh and sour became mellow with keeping, just as now we know

that a Baldwin apple harvested in October will be all the better for

cellarage until Christmas, the ripening process continuing long after

the apple has left its bough. Grains and seeds when newly gathered are

usually soft and, at times, somewhat damp; exposed to the sun and dry

air for a few days they become hard and remain sound for months or even

years of careful storage. In warm weather among many Indian tribes such

food was almost the only kind that remained eatable; all else went to

swift decay, except in parched districts such as those of Arizona, so

that roots, fruits, the flesh of birds, beasts, and fish had to be

consumed speedily, a fact that goes far to account for the gluttony of

the red man. His stomach was at first his sole warehouse; that filled,

any surplus viands went to waste. In frosty weather this havoc ceased;

as long as cold lasted there was no loss in his larder. A few

communities, as at Luray, Virginia, or at Mammoth Cave, Kentucky, in

their huge caverns had storehouses which would preserve food all the

months of the twelve. In New Mexico and other arid regions the air is so

dry that meat does not fall into decay. How it was discovered that smoke

had equal virtue we know not. Probably the fact came out in observing

the accidental exposure of a haunch of venison as the reek from a

camp-fire sank into its fibres. Salt, too, was early ascertained to have

great value in preserving food. Suppose a side of buffalo, or horse, to

have fallen accidentally into brine in a pool or kettle, and stayed

there long enough for saturation, its keeping sweet afterward would give

a hint seizable by an intelligent housewife. Preservation by burial in

silos began in times far remote, and was fully described by Pliny in the

first century of the Christian era.

Properties in Clothing.

The skin just taken from a sheep, the hide when removed from an ox, are

both as flexible as in life. But they soon stiffen so as to be

uncomfortable when worn as garments. Wetting the pelt is but a transient

resource; satisfactory, because lasting, is the effect of rubbing

grease, fat, or oil into the texture of the hide. Peary in Greenland

found that pelts in small pieces, and bird-skins, were softened by the

Eskimo women chewing them for hours together.

Wetting was as notable an aid to handicraft of old as today. Boughs,

roots, withes, osiers, or the stems of fibrous plants, when thoroughly

saturated with water became so soft as to be easily worked, yielding

strands, as in the case of hemp, separated from worthless pulp. Hence

the basketmaker, the wattler, the builder, the potter, the weaver of

rude nets and traps, long ago learned to wet their materials to make

them plastic. Take now the reverse process of drying, which toughens

wood, and the sinews used as primitive thread. Leaves when dried become

hard and brittle of texture, hence the necessity that when woven and

interlaced as roofs the work shall promptly follow upon gathering the

material. In plaiting coarse mats and sails may have begun the textile

art which to-day gives us the linens of Belfast, the silks of Lyons and

Milan.

Cotton Strengthened and Beautified.

A good and serviceable imitation of silk is due to a simple and

ingenious treatment of cotton. In 1845 John Mercer, a Lancashire calico

printer, one day filtered a solution of caustic soda through a piece of

cotton cloth. He noticed that the cloth, as it dried, was strangely

altered; it had shrunk considerably both in length and breadth, had

become stronger, with an increased attraction for dyes. This was the

beginning of the mercerization which to-day produces cotton fabrics

almost as strong and handsome as if silk. The cloth, preferably woven of

long Sea Island staple, is immersed in a solution of caustic soda, and

afterward washed in dilute sulphuric acid and in pure water. As it

enters the caustic bath the cotton is pure cellulose, as it leaves the

bath the fabric is hydrated cellulose, with new and valuable properties.

The structural change in the fibre is decided. The original filament of

cotton is a flattened tube, the sides of which are close together,

leaving a central cavity which is enlarged at each edge of the

surrounding tube. It is opaque and the surface is not smooth. The fibre

has also a slight twist. The tube after treatment becomes rounded into

cylindrical form; its cavity is lessened and the walls of its tube

thicken; the surface becomes smooth and each fibre assumes a spiral

form. Effects like these of mercerization are produced in paper as well

as in cotton cloth, yielding vegetable parchment, a familiar covering

for preserve jars and the like.

Properties in Building Materials.

Some sandstones, such as are common in Ohio and Indiana, soft when hewn

in the quarry, soon harden on exposure to wind and weather; materials of

this kind in early times afforded shelter more lasting than tents of

boughs or hides. But the building art was to know a gift vastly more

important when an artificial mud was blended of clay and water, with a

steady improvement both in the strength and durability of the product.

It was a golden day in the history of man when first a clayey paste was

patted into a pot, a bowl, a kettle: then was laid the foundation of all

that the potter, the brick maker, the tile molder have since

accomplished. Another remarkable discovery, needing prolonged and

faithful experiment, was reached when pottery was found to keep its form

better when broken potsherds and bits of flint were mingled with its

clay. A discovery of equal moment was that of mortar, probably

approached in the daubing of mud or clay into chinks of stones, with the

admixture first of one substance and then another until the right one

was found, and the binder and the bound became of one and the same

hardness. The Romans, a deliberate race, took two years in making a

batch of mortar; that bond to-day protrudes from their walls as more

resistant to the tooth of time than stone itself.

Flame and Electricity as Modifiers.

But if water did much to modify properties, flame did infinitely more. A

block of blue limestone thrust into a fire was burned to whiteness, and

became lime, which, mixed with water, proved a biting compound of

slippery feel,--an alkali indeed. This same wonderful flame caused water

wholly to disappear from a heated kettle; or could dissipate almost the

whole of an ignited brand or lump of fat. By cooking a food, it gave a

new relish to the poorest dish, banished from such a root as tapioca its

poison, and when a yam was baked it remained eatable for a twelvemonth.

Fire enabled man to melt metals as if they were wax, to soften iron or

copper which a deftly swung hammer shaped as he willed. Here, too,

opened the whole world of chemistry, one of its first gifts the power to

take an ore worthless when unchanged, and gain from it a battle-axe, a

knife, an arrowhead. Even in this day of electricity it is fire which

the engineer must evoke to create acids, alkalis, sugars, alcohols, from

substances as different from these as iron is from iron ore.

Electricity as a modifier of properties in turn throws flame into

eclipse. Take an example: a strip of ferro-nickel is fast dissolving in

an alkaline bath; attach one end of the metal to the negative pole of a

battery or a dynamo, the other end to the positive pole; at once

solution ceases and the metal begins to pick out kindred particles from

the bath, adding them to itself. Electricity has completely reversed the

wasting process; what was eaten away is now growing, what was a compound

is now shaken into its elements, one of which rapidly increases in mass.

Nothing in the empire of heat is as striking as this process--familiar

in renewing the energy of a storage battery. Many a union or a parting

impossible to fire is wrought instantly by the electric wave.

The Bamboo Rich in Utilities.

When Mr. Edison devised his electric lamp, his first successful

filaments were fibres of bamboo; they glowed more brilliantly than

anything else he could find, they were tenacious enough to withstand

intense heat for weeks together. A single gift of nature, such as the

bamboo, may be so many-sided that its applications greatly enrich human

life. A task of interest would be to trace the vast indebtedness of

modern science and art to carbon, iron, or silver, in their various

forms. But the bamboo is cheaper and more abundant than any of these, so

that it will be worth while to glance at the many wants it has

satisfied, at the creations it has suggested to ingenuity. In Ceylon,

India, China, Japan, the Malay archipelago, it is the chief item of

natural wealth, the main resource for the principal arts of life. First

of all it provides food. More than one case is recorded where its

abundant seeds have staved off the horrors of famine; these seeds, too,

are commonly fermented to produce a drink resembling beer. Many species

of bamboo have shoots which when young and tender are a palatable and

nourishing food. As a building material it is strong, durable and easily

divided. Its sizes are various enough to provide a fishing-rod for a

boy, or a column for a palace.

“To the Chinaman, as to the Japanese,” says Mr. Freeman-Mitford, in “The

Bamboo Garden,” “the bamboo is of supreme value; indeed it may be said

that there is not a necessity, a luxury, or a pleasure of his daily life

to which it does not minister. It furnishes the framework of his house

and thatches the roof over his head, while it supplies paper for his

windows, awnings for his sheds, and blinds for his verandah. His beds,

tables, chairs, cupboards, his thousand and one small articles of

furniture are made of it. Shavings and shreds of bamboo stuff his

pillows and mattresses. The retail dealer’s measure, the carpenter’s

rule, the farmer’s waterwheel and irrigating pipes, cages for birds,

crickets, and other pets, vessels of all kinds, from the richly

lacquered flower-stands of the well-to-do gentleman down to the humblest

utensils of the very poor, all come from the same source. The boatman’s

raft, and the pole with which he punts it along; his ropes, his mat

sails, and the ribs to which they are fastened; the palanquin in which

the stately mandarin is borne to his office, the bride to her wedding,

the coffin to the grave; the cruel instruments of the executioner, the

beauty’s fan and parasol, the soldier’s spear, quiver, and arrows, the

scribe’s pen, the student’s book, the artist’s brush and the favorite

study for his sketch; the musician’s flute, the mouth-organ, plectrum,

and a dozen various instruments of strange shapes and still stranger

sounds--in the making of all these the bamboo is a first necessity.

Plaiting and wickerwork of all kinds, from the coarsest baskets and

matting down to the delicate filigree which encases porcelain, are all

of bamboo fibre. The same material made into great hats like inverted

baskets protects the coolie from the sun, while the laborers in the rice

fields go about looking like animated haycocks in waterproof coats made

of the dried leaves of the bamboo sewn together.”

Materials for Basketry.

In North America the Indians have had no such resource as the bamboo,

but with tireless sagacity they have laid under contribution either for

food or for the arts every gift of the soil. In seeking materials for

basketry, for example, they have surveyed the length and breadth of the

continent, testing in every plant the qualities of root, stem, bark,

leaf, fruit, seed and gum, so far as these promised the fibres or the

dyes for a basket, a wallet, a carrier. With all the instinct of

scientific research they have sought materials strong, pliant, lasting

and easily divided lengthwise for refined fabrics. In his work on

“Indian Basketry” Mr. Otis T. Mason has a picture of a bam-shi-bu coiled

basket, having a foundation of three shoots of Hind’s willow, sewn in

the lighter portions with carefully prepared roots of kahum, a sedge;

while its ornamental designs are executed in roots of a bulrush, the

tsuwish. Often a basket, as in this case, is built of materials found

miles apart, each requiring patient and skilful treatment at the

artist’s hands.

A few trees, the cedar in particular, lend themselves to the needs of

the basketmaker with a generous array of resources. Mats of large size

made from its inner bark are common among the Indians of the Northern

Pacific Coast. From the roots of the same tree hats are woven as well as

vessels so close in texture as to be watertight. When the roots are

boiled so as to be readily torn into fibres, these are formed into

thread, either woven with whale-sinews or with kelp-thread as warp.

Among the handsomest of all Indian baskets are those of the Pomo tribe,

one of which is shown on page 109. The splints for their creamy

groundwork are made from the rootstock of the _Carex barbarae_, which

are dug from the earth with clam shells and sticks, a woman securing

fifteen to twenty strands in a day. These she places in water over night

to keep them flexible, and to soften the scaly bark which is afterward

removed. To make a basket watertight the Indians of Oregon weave the

inner bark of their maple with the utmost closeness. In other regions a

simpler method is to apply as water-proofing the gum of the piñon, the

resins of pines, or mineral asphalt. Equal diligence and sagacity mark

the Indians as users of stone. The Shastas heat a stone of such quality

that in cooling it splits into flakes for weapons and tools. They place

an obsidian pebble on an anvil, and with an agate chisel divide it as

they wish; all three being chosen from a vast diversity of stones which

must have been tried and found, inferior.

Aluminium and Its Uses.

From Indian handicrafts, developed by aboriginal skill, patience and

good taste to remarkable triumphs, let us turn to an achievement of a

modern chemist who, calling electricity to his aid, bestowed a new metal

upon industry, making possible new economies in a wide sisterhood of

arts. Aluminium was discovered in 1828 by Wohler, a German chemist, who

noted its lightness, toughness, and ductility. At the Centennial

Exhibition at Philadelphia, in 1876, a surveyor’s transit built of

aluminium was shown, but the metal at that time was six-fold the price

of silver, so that the instrument for some years remained uncopied. Of

course, engineers and mechanics were much interested in a metal only

about one-third as heavy as brass or copper, of white lustre, and with

as much as five-eighths the electrical conductivity of copper. All that

hindered the extensive use of the metal was its high cost. If that cost

could be lowered, at once copper, and even silver, would face a rival.

After many unsuccessful because expensive processes for obtaining the

metal had been devised, a method was found at once simple and

inexpensive.

This method of separating aluminium from its compounds was devised by

Charles M. Hall, while an undergraduate student at Oberlin College,

Ohio. His success turned on his knowledge of the properties of related

metallic compounds. He recognized the probable value of aluminium in

the arts, could it be produced in large quantity at low cost. He

believed that electrolysis would prove the most convenient, thorough and

inexpensive method; but there was at that time no process known by which

it could be applied to this element. His problem was to find a form of

electrolyte rich in aluminium which should be comparatively easy to

separate into its elements, and to discover a substance for the solvent

which should prove a satisfactory bath. This latter substance must,

furthermore, be a good conductor of electricity, must readily dissolve

the proposed electrolyte, and must have a higher resistance to

electrolytic disruption than the electrolyte. To discover the needed

substances for electrolyte and solvent involved the examination of all

available compounds of aluminium, the study of the various possible

solvents for the compound selected, and the determination of electric

conductivities. By virtue of rare familiarity with the chemistry and

physics of the subject, with the properties of every substance

concerned, the search was, after a time, rewarded with complete success.

It was found that bauxite--the oxide of aluminium, alumina, in fact--is

dissolved by molten cryolite, the double silicate of aluminium and

sodium, and that the latter, while dissolving the bauxite freely and

serving as an ideal solvent, also itself breaks up under the action of

the electric current at a much higher voltage than alumina. So far as

known, these are the only substances in nature which stand to each other

in such relation as to permit the commercial production of the metal.

Aluminium as constructive material has disappointed some of its earlier

advocates. It is difficult to work, gumming the teeth of files and

resisting cutting and drilling tools by virtue of the very toughness

which makes it desirable for tubes, columns, and the like. Its

excellences, however, are manifold: the German army on investigation

found that helmets of aluminium, as light as felt, turned the glancing

impact of a bullet. For soldiers’ use it now forms not only helmets, but

cooking vessels, cartridge cases, buttons, sword and bayonet scabbards.

It gives the photographer as well as the surveyor instruments which

unite strength with lightness. It has furthermore the quality which has

long given value to the lithographic stone of Hohenlofen in Bavaria.

Aluminium takes a sketch as perfectly as does the stone, with the

inestimable advantages that the metal may be readily curved for a

cylinder press, that it is compact and light in storage, while without

the brittleness which has made stone so costly a servant to both artists

and printers. To produce a deep color from stone it may be necessary to

print one impression over another again and again; from aluminium a

single impression is enough, as severe pressure may be safely applied.

Aluminium has so great an affinity for oxygen as to play a conspicuous

part in the metallurgy of other metals. In the casting of iron, steel or

brass, the addition to each ton of two to five pounds of aluminium

greatly improves the product; the aluminium by combining with the

occluded gases reduces the blowholes and renders the molten metal more

fluid and therefore more homogeneous. A second use for aluminium turns

on the same quality; it was devised by Dr. Goldschmidt for producing

high temperatures, and is especially useful in welding steel rails and

pipes. A mixture of iron oxide and aluminium finely divided is ignited

by a magnesium ribbon; a very high temperature results as the aluminium

combines with the oxygen derived from the iron oxide.

Aluminium by reason of its lightness occupies a large field in naval and

military equipments, in motor-car construction, and the like, where the

reduction of weight is of paramount importance. For cooking utensils the

use of aluminium is constantly extending; the metal is a capital

conductor of heat, is not liable to deteriorate in use, and gives rise,

if dissolved, to harmless compounds. The chief objection to aluminium is

its low tensile strength, which, for the cast metal is only 10,000 to

16,000 pounds per square inch. An improvement is effected by adding as

an alloy a small quantity of some other metal, such as nickel or copper.

When one part of aluminium is joined with nine parts of copper we have

aluminium bronze, the strongest and handsomest of copper alloys, much

resembling gold in its lustre.

Aluminium is finding acceptance as an electrical conductor. An

installation of this kind in Canada unites Shawinigan Falls with

Montreal, 84.3 miles distant. Three cables are employed, each composed

of seven No. 7 wires. The total loss in the transmission of 8,000-horse

power, at 50,000 volts at the generating station, is about eighteen per

cent. Comparing equal conductors, in round numbers the cross-section of

an aluminium cable is one-and-a-half times that of a copper cable, the

weight being one-half and the tensile strength three-quarters.

Everything considered when aluminium is 2-1/10 the price of copper, the

investor is equally served by both metals as conductors. This is true

only where the conductors are bare. Where insulated cables are needed,

the increased diameter of an aluminium conductor entails extra cost for

insulating material.

Properties at First Unwelcome are Turned to Account.

At first the lightness and weakness of aluminium were much against it;

these, as we have seen, were soon overcome by alloying the metal with

copper or nickel. But by giving aluminium forms of utmost stiffness, by

reinforcing these forms with steel wires, the metal is quite strong and

rigid enough for cups, plates, cameras and other instruments for which

lightness is most desirable. In many another case a material or a

characteristic at first unwelcome has been turned to excellent account.

Smokiness in a fuel is not a quality mentioned in its advertisements,

and yet smokiness is just what is sought in the twigs, stubble, or coals

set on fire to give plants a cloud protecting them from unseasonable

frosts. It is astonishing how little fuel will serve in such cases,

especially if the atmosphere is calm, so as not to carry the smoke where

it is not needed. Many another instance might be given of a quality

objectionable for one service and then turned to satisfying a new want.

Sometimes, too, offensive qualities are most useful. Illuminating gas,

as at first manufactured, had a distressing odor, which gave prompt and

unmistakable notice of a leak. When water gas came into use, most

harmful when inhaled, the chemists were puzzled to know how to give it

an offensive smell; they found that a quality long complained of was

really an advantage in disguise.

So in the electrical field, when an unsought quality has intruded

itself, and proved unwelcome, the question has arisen, what service can

we enlist it for? Not seldom the answer has been gainful in the extreme.

Dr. Oliver J. Lodge tells us that a bad electrical contact was at one

time regarded simply as a nuisance, because of the singularly uncertain

and capricious character of the current transmitted by it. Professor

Hughes observed its sensitiveness to sound-waves, and it became the

microphone, which, duly modified, brought the telephone from the whisper

of a curious toy to the full tones which ensured commercial success the

world over. This same “bad” contact turns out to be sensitive to

electric waves also, forming indeed nothing else than the coherer of the

wireless telegraph.

Many an electrician has been perplexed and thwarted by the small bubbles

of air which place themselves on a metallic surface immersed in an

electric bath, interrupting the attack sought to be carried to a finish.

Happily there is a task which these very bubbles perform as if they had

been created for no other purpose, namely, the re-sharpening of files.

First the dull and dirty files are placed for twelve hours in a fifteen

to twenty per cent. solution of caustic soda; they are then cleaned with

a scratch-brush and a five per cent. soda solution. Next they are placed

in a bath of six parts of forty per cent. nitric acid, three parts

sulphuric acid, and 100 parts water, each file being connected to a

plate of carbon immersed close to it, by means of a copper plate

connecting at the top all the carbons and the files. This produces a

short-circuited battery generating gas at the surface of the files; the

bubbles which adhere to the points of the files protect them from being

eaten away, while the rest of the metal is being etched. Every five

minutes the files are taken out and washed in water to remove the oxide

which collects on their surfaces. When sufficiently etched they are

placed in lime-water to remove any adherent acid, dried in sawdust to

prevent rusting, and rubbed with a mixture of oil and turpentine.

Indispensable in the whole process is the protection afforded by the

bubbles of air.

Evil, Be Thou My Good.

For a long time its creation of sparks kept electrical machinery out of

mines liable to fire-damp, which might be exploded by these sparks. In

many other places they worked evils quite as serious, setting fire to

shavings, cotton and such like. To-day these very sparks are applied to

touching off the charges of gas and air in gas-engines of all types,

whether stationary, or for automobiles and motor-boats. In another

respect the automobile should be provided with a means of creating what

is usually considered a nuisance, namely, a noise. Moving rapidly as it

does on thick rubber tires, it gives no warning to hapless wayfarers. In

Canadian cities, where in winter deep snow may muffle the tread of

horses, every sleigh, under severe penalty, must be furnished with

efficient bells.

Compensating Devices.

Sometimes an important property has unwelcome effects which, in

particular cases, cannot be applied to advantage, and must be

counterbalanced with as much care as possible. Many pieces of mechanism

from the qualities of their materials are subject to deviations which

must be compensated by introducing equal and opposite action. Tasks of

this kind proceed upon an intimate acquaintance with the properties of

substances common and uncommon. From the first making of clocks there

was much trouble due to changes of temperature which affected the

dimensions of pendulums, and consequently their rate of going. This

difficulty is overcome by taking advantage of the fact that heat expands

zinc about two-and-a-half times as much as it expands steel. Accordingly

the two-second pendulum of the great clock at Westminster is built of a

steel rod 179 inches in length, and a zinc tube, less massive, 126

inches long; they are joined at their lower ends only and are parallel.

As temperatures vary, the fluctuations in length of the steel compensate

those which occur in the zinc. Another mode of effecting the same

purpose is to employ a cylinder partly filled with mercury; as this

rises when warmed it exactly compensates for the lengthening by

expansion of its supporting rod of steel.

Gravity, that universal force at which we have just glanced as it swings

a pendulum, cannot be banished, but its downward push may be balanced by

an equal upward thrust. In a remarkable feat Plateau poured oil into a

blend of water and alcohol, adding alcohol until he produced a mixture

having the same specific gravity as the oil--which now became a sphere,

taking its place in the middle of the diluted spirits. He then

introduced into the oil a vertical disc which he rotated; very soon

spherules of oil separated themselves from the parent mass, and as

satellites moved in the same direction as the primary sphere, because

immersed as they were in the diluted alcohol, they shared the direction

of its motion: the whole afforded a remarkable illustration of how

nebulae may become planets, moons, and suns.

On somewhat the same principle as Plateau’s model are the liquid

compasses for ships. Their needles are disposed within hollow metallic

holders of the same specific gravity as the immersing liquid, in which

therefore they move with perfect freedom on their sapphire bearings.

Sometimes it is desired to use compass needles so poised that they will

respond to the slightest magnetic influence. To this end one needle is

placed above another, the north pole of the first over the south pole of

the second; the astatic needle formed by this union is much more

sensitive than a simple needle. The astatic needle, for all its

ingenuity, is little used; of incomparably more importance is that other

magnetic device, the telephone. No sooner had it entered into business

than a serious fault was found with its messages; they arrived blurred

and mingled with many sounds and noises, as if the conveying wire had

caught every audibility of a neighborhood. The difficulty is remedied by

using two conductors instead of one, and so arranging them that the

currents induced on one conductor are exactly equal and opposite to

those induced in the other.

Properties Long Deemed Useless are Now Gainful.

If properties at first unwelcome have at last been turned to account, so

also have properties which were long deemed utterly useless. A big and

interesting book might be filled with the story of how by-products, long

thrown away as worthless, have rewarded careful study with great profit.

Thus for ages was bran discarded in flour-mills: to-day it may afford

all the miller’s profit, or even more than that profit. In the Southern

States until a generation ago cotton seed was regarded as valueless. At

present that product, so long wasted, is the basis of a great industry,

a ton of seed yielding about 1089 lbs. of meat to 20 lbs. of lint; out

of this meat 800 lbs. are cake and meal; the remainder, 289 lbs., forms

an oil which furnishes a substitute for olive oil and lard. Until a few

years ago glycerine was thrown away as produced in candle-works and

soap factories. It is now so valuable that manufacturers adopt just that

method of preparing fatty acids which yields most glycerine from neutral

fats. So in paper-making, the soda which formerly was sent into creeks

and rivers to the pollution of sources of water-supply, is now used over

and over again, largely increasing the net results of manufacture. No

industry has shown of late years so large utilization of products

formerly wasted as the iron and steel manufacture. Its slags are made

into bricks, cement, and glassy non-conductors of heat and electricity.

Its gases are used for engines developing immense motive powers, or they

are in part condensed for valuable acids or other compounds. In these

cases and thousands more the question has been, What are the properties

of these by-products? How can they be made useful?

Separation Turns on Diversity of Properties.

Let us note how diverse substances are separated from one another by

taking hold of differences in their properties. When a handful of grain

which has just passed under a flail is thrown upward in a breeze, its

chaff is blown much farther than the grain; the difference in breadth of

surface, joined to a difference in density, enables the wind to effect a

thorough separation. A common fanning mill, with its quick air current,

works much better than the fitful wind, because continuously. That

simple machine, like every other which takes a mixture and separates its

ingredients, seizes upon a difference in properties. In Edison’s

apparatus for removing iron from sand or dust, a series of powerful

magnets overhang a stream of sand or powdered material, deflecting the

iron particles so that they fall into a bin by themselves, while the

trash goes into an adjoining larger bin. The Hungarian process of

flour-milling first crushes wheat through rollers; the various products

are then separated by processes which lay hold of differences in

specific gravity--often but slight.

A feat more difficult than that of the Hungarian mill would seem to be

the division of diamonds from other stones. It has been accomplished by

Mr. Frederick Kersten of Kimberley, South Africa. He noticed one day at

his elbow a rough diamond and a garnet on a board. He raised one end of

this board, and while the garnet slipped off, the diamond remained

undisturbed. What was the reason? He observed that the wood bore a

coating of grease, which possibly had held the diamond while the garnet

had slipped away. He took a wider board, greased it, and dropped upon it

a handful of small stones, some of which were rough diamonds. He found

that by inclining the board a little, and vibrating it carefully, all

the stones but the diamonds fell off, while the diamonds stuck to the

grease. He forthwith built a machine with a greasy board as its

separator, and scored a success.

On quite a different plan is built the coal washer which separates coal

from slate. Pulses of water are sent upward through a sieve so as to

strike a broken mixture of coal and slate, making a quicksand of the

mass. Because the slate is heavier than the coal it is not carried so

far, and is therefore caught in a separate stream and thrown away.

Properties Newly Discovered and Produced.

Separations, such as we just considered, turn upon obvious differences

in density. Properties not obvious, yet highly useful, come into view

year by year as observers grow more alert and keen, as new instruments

are devised for their aid, as measurements become more refined, so that

matter is constantly found to be vastly richer in properties than was

formerly supposed. We have long known that carbon has forms which vary

as widely as coal, graphite and the diamond. Many other elements are

detected in a similar masquerade. Iron, for instance, takes three forms,

_alpha_, _beta_, and _gamma_. _Alpha_ iron is soft, weak, ductile and

strongly magnetic; _beta_ iron is hard, brittle and feebly magnetic;

_gamma_ iron is also hard and feebly magnetic, yet ductile. Joule, the

famous English experimenter, prepared an amalgam of iron with mercury;

when he distilled away the mercury, the remaining iron took fire on

exposure to the air, proving itself to be different from ordinary iron.

Moissan has shown that similar effects follow when chromium, manganese,

cobalt and nickel are released from amalgamation with mercury.

At first steel was valued for its strength and elasticity; to-day we

also inquire as to its conductivity for heat or electricity, its

behavior in powerful magnetic fields, its capacity to absorb or reflect

rays luminous or other. As art moves onward we enter upon new powers to

change the properties of matter, compassing new intensities of heat and

cold, each with new effects upon tenacity, elasticity, conductivity. So

also with the extreme pressures, possible only with modern hydraulic

apparatus, which prove marble to be plastic, and reduce wood to a

density comparable with that of coal, explaining how anthracite has been

consolidated from the vegetation of long ago.

And one discovery but breaks the path for another, and so on

indefinitely. Coming upon a new property, the sensitiveness of silver

compounds to light, meant a new means of further discovery, the

photographic plate. That plate, responsive to rays which fall without

response upon the retina, reveals much to us otherwise unknown and

unsuspected. Of old when an observer saw nothing, he thought there was

nothing to see. We know better now. Thanks to the sensitive plate we

have reason to believe that properties, once deemed exceptional, are

really universal. Phosphorescence, for ages familiar in the firefly, in

decaying logs and fish, now declares itself excitable in all substances

whatever, although usually in but slight measure. The case is typical:

the polariscope, the spectroscope, the fluoroscope, the magnetometer,

the electroscope, each employing as its core a substance of

extraordinary susceptibility, detects that quality in everything brought

within its play. Thus from day to day matter is disclosed in new wealths

of properties, and therefore in new and corresponding complexities of

structure. In ages past mankind was on nodding terms with many things,

and had no intimate knowledge of anything.

With materials before him richer in array than ever before, and better

understood than of old, the inventor asks, What properties do I wish in

a particular substance? Then, he proceeds to make, if he can, a dye of

unfading permanence, an insulator resistant to high temperatures, an

alloy which when subjected to heat or cold remains unaltered in

dimensions. He finds materials much more under command than a century

ago could have been imagined, as the glass manufacture, the alloying

industry, the making of artificial dyes, abundantly prove.

Edison’s Warehouse as an Aid.

Mr. Edison, for aid in finding just the substance he needs for a new

purpose, has at his laboratory in Orange, New Jersey, a large store-room

filled with materials of all kinds. He may wish a particularly high

degree of elasticity, hardness, abrasive power, or what not; to provide

these he has gathered a wide diversity of woods, ivories, fibres, horn,

glass, porcelain, metals pure and alloyed, alkalis, acids, oils,

varnishes and so on. Take one example from among many which might be

given from his shelves; he finds that a sapphire furnishes the best

stylus wherewith to cut a channel on a phonographic cylinder. Hard,

flinty particles from the air are apt to enter the wax, so as to blunt a

cutting edge. Diamonds would be best as channelers, but their cost

obliges him to choose sapphires as next best; they are purchasable at

reasonable prices and last ten years under ordinary conditions of wear.

CHAPTER XII

PROPERTIES--_Continued_

Producing more and better light from both gas and electricity . . .

The Drummond light . . . The Welsbach mantle . . . Many rivals of

carbon filaments and pencils . . . Flaming arcs and tubes of mercury

vapor.

Light Giving Properties.

Mr. Edison has achieved triumphs not only in giving sound its lasting

registration, but in producing an electric light of new economy. Both

exploits proceeded upon a masterly knowledge of properties. A century

ago candles provided illumination both to rich and poor, the sole

difference being that wax shone in the palace and tallow in the hut. The

oil lamps which gleamed in the lighthouses of England and America, for

all their bigness, were plainly of kin to the Eskimo saucer filled with

blubber, edged with moss as wick. Yet for ages, from every hearth in

Christendom, there had been the promise of better things as bituminous

coals, or sticks of wood, had cheered as much by their light as by their

warmth. We owe much to James Watt, who improved the steam-engine and

gave it essentially the form it retains to the present hour. We owe also

a weighty debt to an assistant of his, William Murdock, who, thanks to a

suggestion from Lord Dundonald, attentively observed the process by

which coals produce light. He saw that under stress of intense heat the

solid fuel emitted streams of gas which burned with great brilliancy.

Here gas-making and gas-burning went on at the same moment in the same

place; might the process be separated, so that gas might be made here,

and burned elsewhere at any convenient time? An experiment proved the

project to be feasible, and forthwith the Soho Works, near Birmingham,

in which Watt’s engines were built, were lighted by gas. Such was the

beginning of an industry now important in many ways. To-day gas not only

yields light, but heat and power, while, especially in metallurgy,

fuels are more and more used after reduction to the gaseous form.

How the Gas Mantle was Invented.

Early in the day of gas-making it was noticed that gases of various

kinds differed much in light-giving quality. It was presently shown that

their light depended on the carbon brought to incandescence in a flame;

in the absence of that carbon, as when a jet of pure hydrogen was

consumed, extreme heat was accompanied by no light whatever. Then came a

capital discovery, namely, that lime introduced within a burning jet of

hydrogen became intensely luminous while itself but slowly consumed.

Adopting lime for the core of his apparatus, Captain Thomas Drummond, of

the Royal Engineers, in 1835 devised the lime light. Upon a block of

pure, compressed quick lime, he directed a jet of burning gas, obtaining

a beam of great vividness still employed in stereopticons and in

theatres. For modern types of the Drummond lamp a twin jet of hydrogen

and oxygen is used. Lime has many sister substances having light-giving

quality when highly heated, and among them are many rare earths, oxides

of uncommon elements. These strange substances were destined to play a

prominent part in the battle between gas and electricity as illuminants.

When Edison in 1878 perfected his incandescent bulb, it seemed as if

electricity were soon to be the sole illuminator of houses. But the gas

engineers were to be rejoiced by the invention of a mantle which

quadrupled the brillancy of a gas flame, withstanding the rivalry of

electricity in a notable degree. This mantle was invented by Dr. Auer

von Welsbach, a chemist of Vienna, who virtually adopted the principle

of the Drummond light. His efforts give us an admirable example of an

inventor passing from a hint to a test, day after day meeting new

difficulties with unfailing courage and resourcefulness.

In 1880 Dr. von Welsbach took up the study of rare earths, mainly with a

view to ascertaining their value as illuminants. As he brought one

specimen after another to melting heat on bits of platinum wire, he

found that the little beads formed were unfavorable in shape to the

production of light. Then came into his mind an idea of that golden

quality which occurs only to the man who earns it: Why not soak cotton

with solutions of salts of rare earths, burn the cotton and leave behind

an earthy skeleton of slight thickness and much surface? Experiment

proved that the idea had promise, but the skeletons crumbled to dust

with the least tremor. For success a fair degree of cohesion was

imperative, but to secure that cohesion demanded skill, resource, and

patience. After a long series of trials a mantle was made with lanthanum

oxide; immersed in flame its beam was particularly bright, now for the

first time suggesting that the rare earths might yield light on a large

scale. But trouble was at hand, to be overcome only at the end of much

toil.

During an absence of several days, the inventor left a mantle of

lanthanum oxide locked up in his laboratory. When he returned it had

fallen to powder, having attracted from the atmosphere both moisture and

carbon dioxide. Evidently this harmful attraction must be avoided by

adding an ingredient to keep the mantle dry and preserve it from union

with carbon dioxide. For this purpose magnesia was chosen; the resulting

compound proved to be durable, and gave an agreeable light of moderate

intensity. But, alas, after glowing about seventy hours, the mantle

failed in its radiance, becoming of glassy and translucent texture. Thus

impeded, the untiring inventor turned to mixtures having zirconium as a

basis; these not only gave a steady beam, but extended to hundreds of

hours the life of a mantle. Still bent on getting more light if he

could, Dr. von Welsbach tested thorium oxide with gratifying results;

yet, strange to say, when he had purified this material to the utmost,

his light fell off in an unaccountable fashion. What could be the

matter? Surely in the purifying process some invaluable element had been

cast aside. This element, in the researches of an associate, Mr. Ludwig

Haitinger, proved to be cerium in minute quantity. Here was a discovery

of the highest moment; at the end of many experiments it was determined

that one per cent. of cerium and ninety-nine per cent. of thorium oxide

are the best proportions for a mantle such as we use to-day. Why these

proportions are best nobody knows, any more than why one per cent. of

carbon added to iron gives us a steel incomparably better than iron for

many uses. A Welsbach mantle has good points apart from its economy of

gas. Its combustion is thorough, so that it throws into the air a

much lower percentage of injurious products than does an ordinary gas

flame. It never smokes, and its light is so steady as to be available

for work with the microscope and other exacting demands. It has one

defect which may yet be removed: its light has a somewhat unpleasant

tinge of green. In another chapter of this book, producer gas, much

cheaper than common illuminating gas, is described. Dowson producer gas,

with a Welsbach mantle, yields a light of 8 to 10 candle-power with a

consumption of 4.5 to 4.8 cubic feet per hour.

[Illustration: DR. CARL FREIHERR AUER VON WELSBACH OF VIENNA.]

[Illustration: Boivin burner for alcohol, attachable to any lamp.]

Thus far no successful mantle for a petroleum lamp has been devised.

With alcohol a mantle yields a brilliant flame. A lamp with a Boivin

burner and a Welsbach mantle has given a light of 30.35 candle-power for

57 hours and 5 minutes in consuming one gallon of alcohol, almost twice

as much light as given by a Miller lamp with a round wick and a central

draft, burning a gallon of kerosene. In the United States on January 1,

1907, there will cease to be an excise tax on alcohol used in the arts,

a denaturalizing process rendering the liquid unfit to drink. As this

alcohol may be easily produced from grain or potatoes at 20 to 25 cents

a gallon, a capital illuminant will be available for the public, as well

as an excellent fuel and a substitute for gas or gasoline in motors.

As first manufactured, gas-mantles were woven, they are now knitted,--a

change for the better in closeness and firmness of texture. Nearly all

the thorium used for mantles is found in the monazite sands of the

provinces of Bahia and Espirito Santo, along the coast of Brazil. These

sands were for a long time valuable only for the zinc they contained.

To-day the thorium they carry is of vastly more account; for chemical

treatment this is sent to Germany whence the manufactured product is

borne to every quarter of the globe.

Improvements in Electric Lighting: Incandescent Lamps.

While the Welsbach mantles have been constantly improved in quality, and

given new and inverted forms of special value, the inventors in the

field of electric lighting have not stood still. For interior

illumination the Edison incandescent bulb still holds its own despite

many a threat of dispossession. Since 1881 its details of manufacture

have been steadily bettered and its price much reduced, while its

consumption of current has fallen from 5.8 watts per candle to 3.1. This

advance, marked as it is, leaves a long path ahead of the inventor whose

estimate is that were the whole of an electric current transformed into

light, a candle would cost us but .11 of a watt, that is, but one

twenty-eighth part as much as when we set a carbon filament aglow. In

electrical terms a horse-power yields 748 watts, representing, were

there no waste in conversion, no less than 425 lamps each of 16

candle-power.

[Illustration: Alcohol lamp with ventilating hood.]

It is this immense margin for improvement that has spurred ingenuity to

attack the problem of electric lighting from many new sides. The General

Electric Company produces a carbon filament of one fifth greater

efficiency than an ordinary untreated filament. Fibers of the usual

cellulose kind are enclosed in a carbon box, placed in a carbon-tube

resistance furnace heated to between 3,000° and 3,700° C. This converts

the filament into a graphite of increased luminosity which, furthermore,

blackens its enclosing glass much less than a common filament does.

[Illustration: Welsbach mantle.]

In the early days of electric lighting a good many experiments were

tried with threads of platinum, but without success. That metal remains

unmelted at a very high temperature, but as a light-giver its quality is

poor. Of late years investigators have turned to other metals, of high

melting points, and with results so remarkable that we may expect some

of them to be in general use in the near future. Tantalum, a rare and

costly metal, has been found to give a candle-power with as little as

two watts and, in specially favorable circumstances, with only 1.85

watts. Osmium, in the hands of Dr. Auer von Welsbach, reduces this

figure to 1.5 watts. Dr. Hans Kuzel, of Baden, Austria, has employed

filaments of tungsten in lamps which he claims demanded only one watt

per candle. From among these new lamps it seems highly probable that as

soon as methods of manufacture are settled and standardized the world

will be given an electric light, in small units, much cheaper than ever

before.

[Illustration: Tantalum lamp.]

[Illustration: Tungsten lamp of Dr. Hans Kuzel.]

New Arc Lamps.

For large spaces indoors and for out of doors the arc-lamp maintains its

popularity in much the form originally devised by Mr. Charles F. Brush

of Cleveland. But, as in the case of the incandescent bulb, many a rival

is now disputing the field, so that supersedure may be close at hand. In

what are known as flaming or luminous arcs the carbon pencils are

impregnated with salts of the calcium group of elements, of extreme

luminosity. In these lamps the electric arc itself is the chief source

of light, instead of the glowing end of the positive carbon as in a

common arc lamp. As the calcium salts volatilize into gases they provide

a path of less resistance than air for the passage of the current, so

that the electrodes may be drawn apart to a distance which may be as

much as 2-1/2 inches. These lamps require free ventilation, so that they

must be open. Their economy is extraordinary, a candle-power being

afforded for .353 watt, as against 1.78 watts for an enclosed arc lamp,

a five-fold gain in effectiveness. To renew the carbons, which waste

rapidly, a new device provides fresh pencils, cartridge fashion, as

required. Without this aid, trimming is often necessary, and this fact

joined to the high cost of the carbons lessens the net gain in their

use. On another line of experiment noteworthy results have been reached

with metallic oxides. Magnetite, an oxide of iron, has developed a

candle-power with but one half of one watt. Ferro-titanium, a compound

of iron and titanium, has given a candle-power with only one third of a

watt, and it is expected that still higher efficiencies will soon be

attained with this wonderful compound.

[Illustration: Hewitt mercury-vapor lamp.]

Hewitt Mercury-Vapor Lamp.

From quite another side Mr. Peter Cooper Hewitt enters the field of

light production, utilizing the glow of a vapor instead of a solid

stick. His lamp is a long, slender tube of glass; within each end is

sealed a metallic wire; at one end is a little mercury. When a powerful

pump has exhausted the tube to a high degree it is sealed, and its wire

terminals are placed in an electric circuit. On tilting the tube the

mercury flows from end to end, an arc is formed, and the mercury vapor

becomes luminous. This vapor remains unconsumed, and the lamp asks no

attention whatever. Its rays are greenish, so that where normal colors

are desired, it is well to use supplementary lamps of carbon filaments

to furnish red rays. For streets, squares, freight-sheds and the like,

the Hewitt light is capital just as produced, its rays being widely

diffused and casting no heavy shadows. Its high actinic power makes it

specially useful to photographers, while in factories, drafting rooms,

composing rooms and so on, its color is unobjectionable. Its cost is

small, as a candle-power is produced in large tubes with but 0.55 of a

watt. A Hewitt lamp of automatic type, recently devised, has a small

solenoid or magnet on the suspension bar just above the holder. On

closing the circuit the current flows through this solenoid which

instantly tilts the tube and starts the light. This lamp is particularly

suited to places, such as the lofty ceilings of foundries, where it

would be difficult to tilt the tube by hand. Hewitt lamps use either a

direct or an alternating current.

In an earlier chapter we glanced at reflectors and refractors, newly

invented, which give light its most useful paths with as little

avoidable loss as possible. These devices, applied to Welsbach burners

and the new electric lamps, greatly economize modern illumination in

comparison with that of former times.[13]

[13] In February, 1906, the Illuminating Engineering Society was

established in New York. Its secretary is A. H. Elliott, 4 Irving

Place, New York. The Society publishes its proceedings and

discussions.

CHAPTER XIII

PROPERTIES--_Continued_. STEEL

Its new varieties are virtually new metals, strong, tough, and heat

resisting in degrees priceless to the arts . . . Minute admixtures

in other alloys are most potent.

From a brief consideration of illuminants let us pass to a rapid survey

of a most important group of structural materials, the steels. Here, as

always, we shall find how abundant are the harvests reaped in a

searching study of properties. Within the past fifty years new steels

have been produced in so ample and rich a variety that we have gained

what are virtually many new metals of inestimable qualities.

Steels for Strength.

In 1781 Professor Torbern Bergman, of the University of Upsala, in

Sweden, showed that steel mainly differs from iron in containing about

one fifth of one per cent. of plumbago, or carbon, as we would say now.

Steels may contain all the way from one tenth to one and a half per

cent. of carbon; the lower this percentage, the more nearly does the

steel approach wrought iron in softness; as the proportion of carbon

increases up to one per cent. the steel increases in tenacity, beyond

one per cent. tenacity diminishes and brittleness is augmented. Hardness

depends upon the percentage of carbon a steel contains. Physical

conditions are almost as important as chemical composition; a mass of

red-hot steel, carefully hammered or pressed is thereby strengthened, an

effect due either to minimizing the process of crystallization, or to

breaking up crystals as fast as they form. The microscope reveals many

details of structure in steel, and has enabled the analysts greatly to

economize the manufacture of desired varieties. Under the microscope

steels much resemble crystalline rocks in structure, with constituents

differing widely. Of these the most important is ferrite, a pure or

nearly pure metallic iron, soft, weak, ductile, of high electric

conductivity. Next in importance is cementite, an iron carbide (Fe₃C),

harder than glass and nearly as brittle, but probably very strong under

gradually and axially applied stress. A third constituent, austenite, is

a solid solution of carbon, or perhaps of an iron carbide, in _gamma_

allotropic iron (there being also _alpha_ and _beta_ irons). Austenite

is hard and brittle when cold, is stable at high temperatures, and is

slowly transformed by reaction into compounds of ferrite or cementite.

Several other ingredients of importance, as pearlite, illustrated on the

opposite page, have also been studied.[14]

[14] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second

edition. Published by Albert Sauveur, Cambridge, Mass., 1906.

While carbon is the most decisive element in admixture, other

ingredients have marked influence, silicon and manganese especially. The

process invented by Bessemer, described by himself in another chapter of

this book, as introduced in 1855, revolutionized the steel manufacture

by its directness, cheapness and speed. It consists in burning out from

pig-iron, by a hot air blast, all or nearly all its carbon. Then

spiegeleisen, or other mixture, containing a definite quantity of carbon

and manganese, is added to the molten mass, yielding steel of the

quality desired. This method produces more rails for railroads than any

competing method; in other fields it is being rivalled more and more

severely by the open hearth process.

[Illustration: Pearlite, magnified about 750 diameters.]

[Illustration: Steel containing more than nine-tenths of one per cent of

crystals of pearlite, surrounded by envelopes of cementite (Fe₃C).

Magnified 200 diameters.]

[Illustration: CLEANING CARS BY THE “VACUUM” METHOD.]

The Open Hearth Process.

Steel making by the open hearth process is chiefly due to the late Sir

William Siemens. In a gas producer he gave his fuel the gaseous form, in

which it is more easily controlled and more efficient than when solid.

Of more importance were his regenerators, chambers of brickwork, heated

by the products of combustion, and then employed to warm incoming

currents of air and gas on their way to the furnace. The Siemens furnace

has been modified in many ways and much improved in its details. A good

example of an open hearth furnace, as planned by the late Mr. Bernard

Dawson, is shown on page 165. It centers in a large hearth built of

refractory materials, upon which the metal is melted as flames play over

it. At each end are two regenerators filled with checker firebricks

through which air or gas passes on its way to the furnace, and through

which, at due intervals, the products of combustion emerge as they pass

to the stack. On each side, one of the regenerators is for air, the

other for gas; between them is a substantial wall to prevent any mixing

before their currents reach the hearth. It is in the regenerator, which

utilizes heat which otherwise would be wasted, that the open hearth

displays its best feature. Its products vary in composition as its raw

materials vary, whether pig-iron of a specific kind, a particular ore,

or scrap; and just as in the Bessemer process, a harmful element, as

phosphorus, is removed almost wholly by the addition of a suitable

ingredient, such as lime. In excellence and uniformity of quality open

hearth steels are preferred to those of the Bessemer converter, even for

railroad rails which for years were made solely by the Bessemer process.

[Illustration: Open hearth furnace.]

The Gayley Dry-Blast Process.

A remarkable improvement in blast-furnace practice, cheapening cast or

pig-iron, and therefore lowering the cost of derived steels, is the

dry-blast process due to Mr. James Gayley, of Pittsburg. It has long

been known that blast-furnaces ask more fuel in warm and damp weather

than in cold and dry weather; beginning with this familiar fact Mr.

Gayley proceeded to dry the air blown into his furnaces, by passing it

around large coils of iron pipes through which a freezing mixture

circulated, melting the snow as formed by passing hot brine through the

pipes, a few of them at a time. The air thus dried was then heated by

being sent through hot blast stoves in the usual mode. This simple

drying of the blast saves about 19 per cent. of the fuel, and makes the

action of the furnace much more regular than when ordinary air is used.

It lowers the temperature of the gases which escape from the top of the

furnace, and raises their percentage of carbon dioxide, symptoms of the

great increase in fuel efficiency. Atmospheric moisture has a cooling

effect on the lower part of a furnace, just where the highest

temperature is needed to melt the iron and slag, remove the sulphur and

deoxidize the silica. A comparatively small increase of temperature by

broadening the margin of effective heat, which margin at best is narrow,

has the astonishing effect of economizing fuel to the extent stated, 19

per cent.[15]

[15] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second

edition. Cambridge, Mass., Albert Sauveur, 1906.

Steels to Order.

What is chiefly sought in steel is tensile strength, next in value is

elasticity; in some cases hardness is indispensable. By varying the

proportions of the carbon, silicon and manganese added to his iron, the

steel-maker produces an alloy with the tenacity, elasticity or hardness

he wishes. Nickel, as a further ingredient, in certain proportions

yields an astonishing gain. A steel containing fifteen per cent. of

nickel has shown a tensile strength of 244,000 pounds to the square

inch, four times as much as before admixture; the elastic limit also was

much increased. Hardness and strength tend to exclude ductility, but

nickel steel is at once strong, hard and extremely ductile; hence its

use for armor plate, great guns, and the barrels of small arms. Nothing

but the high price of nickel prevents these alloys from having wide

utilization, for they mean lighter and therefore more economical

machines and engines than those of ordinary steel. Many turbines

actuated by water, steam or gas, are best operated at speeds forbidden

to common steel, which would fly to pieces under the centrifugal stress

exerted, yet these speeds are quite feasible and safe when nickel steel

is employed. This alloy brings nearer the day of mechanical flight,

first promising to transportation on land and sea engines increased in

power while much diminished in weight. In exceptional cases, where the

expense may be borne, we may expect soon to see nickel steel used for

higher towers, longer bridge-spans, thinner boilers, than those of

to-day. Part of the bridge crossing Blackwell’s Island, New York, is

built of nickel steel. Even with costs at their present plane, it is

worth while for the designer of machinery to remember that friction is

reduced when masses become smaller, power for power. It is found

profitable, for instance, to use nickel steel for the cylinders of

automobiles of high power.

In many tools and implements two different kinds of steel are united

with decided gain. Thus the cutting edge of a cold chisel is hard and

brittle, while its shank, much less hard, is tough and able to resist

the shocks it receives. So also a projectile is hardened at its point

and nowhere else. Plowshares are often made very hard on their surfaces,

with a backing which is comparatively soft but elastic enough to suffer

no harm in the blows dealt by rough ground and stones. One of the

drawbacks in the use of steel is its liability to corrosion. An alloy of

30 per cent. nickel and 70 per cent. steel has proved to be corrodible

in but slight measure, affording a material of great value to the arts.

Heat Treatment.

While the chemical composition of a steel is of prime importance, the

quality of the steel will next depend upon its heat treatment in

manufacture. The temperature to which heating is carried, the period

during which it is maintained, the rate at which cooling takes place,

and the circumstances of cooling, each has its effect on the character

of the product. It is chiefly in this field that the steel-maker within

wide limits is able to turn out an alloy either hard or soft, brittle or

ductile, tenacious or weak, at pleasure. While much has been learned

within the past few years as to the proper treatment of steel by heat,

much still remains to be discovered.

To quote typical instances from Professor Henry Marion Howe, of Columbia

University, New York:--“In the case of steel with less than 0.33 per

cent. of carbon the temperature from which slow cooling occurs appears

to have little influence on the tensile strength; but it is the general

belief that if that temperature approaches the melting-point, the

tensile strength decreases. In the case of higher-carbon steel, the

tensile strength at first increases as the temperature from which slow

cooling occurs rises to 800°, or even to 900° or 1000° C. Then, after

varying somewhat, it falls off very abruptly in the case of steel of

0.50 per cent. of carbon, when that temperature approaches 1400°.”[16]

[16] In his “Iron, Steel and Other Alloys.” Second edition.

Published by Albert Sauveur, Cambridge, Mass., 1906.

Tempering and Annealing.

For rock drills, cold chisels, milling and other tools it is necessary

to use steel carefully tempered, so that brittleness is greatly reduced

while considerable hardness and cutting power remain. Other changes of

properties, as remarkable, follow upon subjecting steel to greater heat

than that used for tempering. Says Professor Roberts-Austen:--“Three

strips of steel identical in quality are taken. By bending one it is

shown to be soft; if it is heated to redness and plunged in cold water

it will become hard and will break on any attempt to bend it. The second

strip, after heating and rapid cooling, if again heated to about the

melting point of lead, will at once bend readily, but will spring back

to a straight line when the bending force is removed. The third piece

may be softened by being cooled slowly from a bright red heat, and this

will bend easily and remain distorted. The metal has been singularly

altered in its properties by comparatively simple treatment, and all

these changes, it must be remembered, have been produced in a solid

metal to which nothing has been added, and from which nothing has been

taken away.”

It is the comparative slowness of cooling in oil, the greater slowness

of cooling in air, that make these by far the best tempering processes,

because the molecular re-arrangement, in which tempering consists,

requires time. Often the critical temperature, at which a desired

re-arrangement takes place, is declared by the metal losing all power of

response to a magnet: this fact affords the steel-maker welcome aid; he

has only to shut off heat as soon as his steel ceases to attract a

magnet and plunge the steel into water in order to obtain the hardness

he wishes.

The complex phenomena of heat treatment in steel manufacture are fully

discussed by Professor H. M. Howe, in his “Iron, Steel and Other

Alloys,” second edition, 1906.

Steel for Railroad Rails.

In another chapter of this book a word is said as to the form of rails

at which Mr. P. H. Dudley has arrived as the outcome of years of

experiment. He thus describes the properties which the steel should

possess by virtue of due chemical composition and proper heat

treatment:--

“Ductility to ensure power to resist the shock of the driving wheels, so

that the steel may not break; resistance to abrasion, that it may not

wear out; and high limit of elasticity, that it may not take a permanent

set and be bent into a series of waves between its supporting ties, by

the enormous pressures which the wheels of to-day throw upon it. The

best composition is carbon 0.55 to 0.60 per cent., silicon 0.10 to 0.15,

manganese 1.20, sulphur under 0.06, phosphorus under 0.06; with 50,000

to 60,000 granulations to the square inch. More granulations, or fewer,

mean an increase of brittleness in the steel.”[17]

[17] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second

edition. Published by Albert Sauveur, Cambridge, Mass., 1906. And a

note from Mr. P. H. Dudley to the author, May 2, 1906.

Invar: A Steel Invariable in Dimensions Whether Warmed or Cooled.

While the great strength of steel makes it of pre-eminent value in the

arts, steel in the huge dimensions of modern roofs and bridges has the

demerit of expanding with heat and contracting with cold in a

troublesome degree. A notable case is that of the steel rails on the

elevated railroad of New York. If this fault, common to all metals, can

be materially reduced or abolished, then steel enters upon a new field

of golden harvests. Here, by dint of acumen and skill the goal has been

reached by M. Charles Edouard Guillaume, of the International Bureau of

Weights and Measures in Paris. A few years ago he began investigating

the singular magnetic qualities of nickel-steels. Then in studying

expansibility by heat he discovered that when the nickel was increased

to 36.2 per cent. the alloy was almost indifferent to changes of

temperature, expanding but one part in one million when warmed from zero

to 1° Centigrade. Because of this insensibility, the alloy at the

suggestion of Professor Thury is named _invar_. In observations of invar

which extended through six years, an elongation of one part in 100,000

was detected; subsequently its changes of length each year seemed less

than one-millionth. This slight inconstancy may be overcome by further

experiment; in the meantime while invar is not available for standards

of length of the first order, such as those of the Bureau of Standards

at Washington, there is a vast and useful field for the alloy. It offers

itself for secondary standards, to be compared at intervals with primary

standards at Washington or other capitals of the world.

A leading application will be in surveying. Already wires of invar have

been employed by the Survey of France with the utmost success,

dispensing with the burdensome apparatus formerly needed in compensating

variations due to temperature. With invar wires ten men have advanced at

the rate of five kilometers a day; ten years before, with ordinary steel

measures, fifty men advanced one half a kilometer, that is, with but one

fiftieth as much efficiency.

In time-keeping invar is likely to be as valuable as in surveying. At

the Bureau of Standards and the Naval Observatory at Washington,

pendulums of invar have been adopted with gratifying results. In

ordinary watches and clocks the alloy will banish the compensating

devices now requisite, of brass and steel which expand with heat and

shrink with cold. For chronometers of the highest grade it is desirable

that invar be improved with respect to its stability, an improvement

which appears to be highly probable.

One other discovery by M. Guillaume deserves a word. He has found a

nickel-steel which when warmed has the same expansibility as glass, so

that it may displace platinum wire in leading an electric current into

an incandescent lamp, a Crookes’ tube or similar illuminator. More

singular still is another of his nickel-steels which shrinks slightly

when warmed, holding out the hope of finding an alloy which will neither

shrink nor expand as its temperature rises. With such a substance, of

trustworthy stability, the arts would have a working material of

inestimable value for theodolites, frames for microscopes and

telescopes, and cameras for exact picturing.

Manganese Steel.

The magnetic properties of steel, to-day of supreme importance, have for

ages excited curiosity. As long ago as 1774, Rinman observed that steel

alloyed with manganese is non-magnetic. Here was a material for

time-pieces which would free them from magnetic derangement. In the

hands of Mr. R. A. Hadfield, of the Hecla Works, Sheffield, England,

manganese steel has been produced in remarkable varieties. As the

proportion of manganese is increased, the alloys manifest singular

changes in their properties. When the manganese is four to six per

cent., and the carbon less than one-half per cent., the alloy is brittle

enough to be readily powdered by a hand hammer. When the proportion of

manganese is doubled, the alloy displays great strength, which reaches

its maximum when the manganese is fourteen per cent. No other material

approaches manganese steel in its ability to resist abrasion; it

outwears ordinary steel four times, much reducing the need for repairs,

renewals, or pauses in work while worn-out parts are being replaced. It

gives equally good service as the pins and bushings of dredges of the

bucket-ladder type, lifting gold-bearing gravels and sands. It is used

for centrifugal pumps in dredging sandy harbors, slips, or ponds, where

the grit borne in the water plays havoc with ordinary steel surfaces. In

ore-crushing manganese steel is particularly effective; a pair of jaws

built of it have crushed 21,000 tons of flinty ore and were still good

for 4,000 to 6,000 tons more, while the best chilled iron plates failed

to crush as little as 4,000 tons.

This alloy is so hard that it cannot be machined or drilled by ordinary

means; it must be treated by emery or carborundum wheels. Yet it is so

malleable that it can be used for rivets when headed cold. It is so

tough that it may be bent and twisted at will without rupture, so that

it forms railroad switches, frogs, and crossings of great durability.

High-Speed Tool Steels.

Until 1868, the steel tools used in lathes and drills, planers and so

on, were limited to the moderate pace at which they remained cool enough

to keep their temper. Beyond that quiet gait they became worthless,

snapped apart, or melted as if wax. In 1868 Robert Forester Mushet, of

the Titanic Steel and Iron Company, Coleford, England, discovered an

alloy of steel, tungsten and manganese which took rough cuts at a depth

and with a speed unknown before. This alloy, because hardened simply in

air, was called “air-hardening” or “self-hardening.” Thirty years

afterward at the Bethlehem Steel Works, Pennsylvania, a tool of this

steel was heated to what was feared to be a ruinously high temperature;

experiment proved that the tool could be used at a heat, and therefore

at a speed, never attained before in the workshop. From that hour

hundreds of investigators have proceeded to combine steel with tungsten

in various percentages, adding manganese, molybdenum, chromium, silicon,

and vanadium. Of these ingredients much the most important are tungsten

and molybdenum. Particular pains must be taken thoroughly to anneal the

alloy when worked into bars.

As to the gain introduced by high-speed tool steels let Mr. J. M.

Gledhill testify from the experience of the Sir W. G. Armstrong,

Whitworth & Company’s works at Manchester:--

“Formerly where forgings were first made and then machined with ordinary

self-hardening steel, a production, from bars eighteen and one half by

six and five eighth inches, of eight bolts in ten hours was usual. With

the new steel forty similar bolts from the rolled bar are now turned out

in the same time, further abolishing the cost of first rough forging the

bolt to form. The speed is 160 feet a minute, the depth of cut

three-quarter inch, of feed 1/32 inch, the weight removed from each bolt

sixty-two pounds, or 2,480 pounds per day, the tool being ground only

once in that time. This is a fairly typical case. Just as striking is

the behavior of this steel in twist drills, which supersede the punching

process by passing through stacks of thin steel plates quite as swiftly

and economically as a punch, while avoiding the liability to distress

which accompanies the action of a punch.”

With the quickening of pace due to these steels, the designer is asked

to remodel machine tools so that they may stand up against new pressures

and speeds. A lathe thus re-patterned is mentioned by Mr. Gledhill: it

absorbs sixty-five horse power as against twelve formerly, and has a

belt trebled in width so as to measure twelve inches. Mr. Oberlin Smith

expects high-speed steel to have other effects on machine design than

the conferring of new strength: he looks for a rivalry keener than ever

between rotary and reciprocating tools. In his judgment the milling

tool, which can be speeded indefinitely, will encroach more and more on

the planer, limited as the planer is by its movement being to and fro.

When work on cast iron must proceed at the utmost pace, a jet of air,

delivered to the chips with force enough to clear them off as fast as

they are formed, enables the speed to be quickened, while, at the same

time, the life of the cutter is lengthened.[18]

[18] The foregoing pages on steel have been revised by Professor

Bradley Stoughton, of the School of Mines, Columbia University, New

York. He contributes at the end of this chapter a brief list of

books for the reader who may wish to know something of the

literature of iron and steel.

Alloys for Electro-Magnets.

In electrical art the alloy employed for electro-magnets should be

permeable by magnetism fully and easily, otherwise dynamos and motors

will waste energy as their magnetism is constantly gained, lost, or

reversed. Once more the experimenter is Mr. Robert A. Hadfield of

Sheffield, who produces an excellent alloy by uniting iron with 2.75 per

cent. silicon, .08 per cent. manganese, .03 per cent. sulphur, .03 per

cent. phosphorus. This alloy is improved by being heated to between 900°

and 1100° C., followed by quick cooling; then being reheated to between

700° to 800° C., and cooled very slowly.

Iron is largely used as an electrical conductor, so that it is well to

know how its conductivity is affected by ordinary admixtures. In

experiments with sixty-eight specimens, Professor W. F. Barrett alloyed

iron separately with carbon, aluminium, silicon, chromium, manganese,

nickel, cobalt, and tungsten. In every case there was a loss of

conductivity, and usually in a degree proportioned to the atomic weight

of the added ingredient. Between one element and another there was often

a wide disparity of effect. For example, in admixtures, each of one per

cent., tungsten increased the resistance of a conductor by two per

cent., while aluminium did seven-fold as much harm.

Magnetic Alloys of Non-Magnetic Ingredients.

We have so long been accustomed to thinking that there must be iron in

everything magnetic that we hear with astonishment that metals each

insusceptible of magnetism, when united strongly display this property.

Such is the discovery of Mr. Fr. Heusler, of Dillenburg, near

Wiesbaden. He noticed one day that an alloy of manganese, tin, and

copper adhered to a tool which he had accidentally magnetized. In the

course of experiments Mr. Heusler found that carbon, silicon, and

phosphorus did not confer magnetism; while arsenic, antimony, and

bismuth did so, all three metals being diamagnetic, that is, placing

themselves at right angles to a common steel magnet above which they are

freely suspended. An alloy of remarkable magnetic strength was composed

of copper 61.5 per cent., manganese 23.5 per cent., and aluminium 15 per

cent. This alloy is brittle and considerable changes of temperature but

slightly affect its magnetism. When a little lead is added magnetism

disappears between 60° and 70° C. This alloy therefore is magnetic when

placed in cold water; when the water is heated the magnetism disappears

before the water boils, only to reappear when the water cools. The main

interest of these discoveries is that the new alloys bridge the gap

betwixt magnetic and diamagnetic bodies, that is, they join the iron,

nickel, and cobalt group, which place themselves along the line of a

magnetic field, with the diamagnetic elements, bismuth, antimony, zinc,

tin, lead, silver, and arsenic, which place themselves at right angles

to the lines of a magnetic field. We have been accustomed to suppose

that magnetism is a property possessed by only a few elements; these

alloys show us that magnetism may arise as a result of grouping atoms,

none of which by itself has any magnetism whatever. Indeed it may be

possible to make an alloy more magnetic than iron, furnishing the

electrician with electro-magnets of new power.

Anti-Friction Alloys.

We have briefly glanced at recent progress in the art of alloying in so

far as it has produced steels of new strength, elasticity, or hardness;

new ability to resist abrasion or high temperatures, new capacity for

magnetism, new indifference to changes of temperature as affecting

dimensions. Alloying has of late years conferred other gifts upon

industry, of which one example may be cited from among many of equal

importance. Friction levies so grievous a tax upon the mechanic and the

engineer that they are quick to seize upon any material for bearings

which reduces friction. As the result of extensive experiments Dr. C. B.

Dudley recommends an alloy of tin, copper, a little phosphorus, with ten

to fifteen per cent. of lead. He finds the loss of metal by wear under

uniform conditions diminishes as the lead is increased and the tin

diminished.

Influence of Minute Admixtures.

We have seen how remarkably the properties of iron are affected by

minute additions of carbon which may be assumed to enter into chemical

union with the metal. The properties of other metals may be influenced

by minute quantities of added elements, although in quantities so small

as to preclude the possibility of their forming ordinary chemical

compounds. It by no means follows, however, that the atom of an added

element does not exert a direct influence. In Professor Roberts-Austen’s

laboratory, in London, two ladles were filled with exceptionally pure

bismuth; into one ladle a tiny fragment of tellurium was placed. The

ladles were poured each into a separate mold, and when the metal became

cold it was fractured by a hammer. The bismuth to which the tellurium

was added had become minutely crystalline; while that which remained

pure had crystallized in broad mirror-like planes. One reflected light

as a mirror; the other, containing the tellurium, scattered the light it

received. With no guidance but that of mere inspection, one would have

said that the two substances were distinct elements, and yet the only

difference was that one contained 1/2000 part of tellurium and the other

no tellurium at all.

Submarine telegraphy presents us with a case as striking: were its

copper wire to contain but one-thousandth part of bismuth, the line

would be so much reduced in conductivity as to be commercially

worthless: quite as harmful are mixtures of antimony. In coining, the

addition to gold of one five-hundredth part by weight of bismuth

produces an alloy which crumbles under the die and refuses to take an

impression. In the manufacture of such dies it is necessary to employ a

steel containing 0.8 to 1 per cent. of carbon and no manganese. It is

usual, says Professor Roberts-Austen, to water-harden and temper it to a

straw color, and a really good die will strike 40,000 coins without

being fractured or deformed, but if the steel contains 0.1 per cent.

too much carbon, it would not strike 100 pieces without cracking, and if

it contained 0.2 per cent. too little carbon, it would probably be

hopelessly distorted and its engraved surface destroyed in the attempt

to strike a single coin. As in coining so in steam-engineering. A little

arsenic added to copper improves it for the fire-boxes of locomotives.

Boilers of old, formed of copper slightly admixed with sulphur, lasted

longer than modern boilers built of copper free from sulphur. Antimony

behaves like arsenic, and in due proportion strengthens copper; bismuth,

on the contrary, weakens copper, and a perceptible effect is wrought by

a mere trace. Nickel is made malleable by adding extremely small

quantities of phosphorus, magnesium, or zinc.

BOOKS ON IRON AND STEEL

Chosen and annotated by Professor Bradley Stoughton, School of Mines,

Columbia University, New York.

(Graduated Yale University, 1893, as Ph.B. In 1896 Assistant in

Mining and Metallurgy at Massachusetts Institute of Technology,

Boston, where he received the degree of B.S. In 1898-99,

metallurgist of South Works. Illinois Steel Co., South Chicago.

Superintendent in 1900 of steel foundry, Briggs-Seabury Gun and

Ammunition Co., Derby, Conn. Manager of Bessemer plant, Benjamin

Atha & Co., Newark, N. J., in 1901. Instructor in metallurgy,

Columbia University, 1902-03. Next year became Adjunct Professor of

Metallurgy, Columbia University and, as consulting metallurgist,

entered the firm of Howe & Stoughton, New York.)

BALE, GEORGE R. Modern Foundry Practice. Part I, 1902. Part II,

1906. London, Technical Publishing Co. 3_s._ 6_d._ each.

An admirable work, the only one covering the whole field. The author

thoroughly understands his subject, and writes most intelligibly. The

principles underlying every detail of practice are clearly explained.

Part I deals with foundry equipment, materials used, furnaces and

processes, describes blowers, ladles, cranes, hoists, cupola, air

furnaces, drying ovens, dry and green sand, the manufacture of chilled

castings and malleable iron castings.