CHAPTER I. STATIC ELECTRICAL APPARATUS

Produced by James Simmons.

This file was produced from page images at the Internet Archive.

Transcriber’s Note

This book was transcribed from scans of the original found at the

Internet Archive. The page scans were done by Google. The original book

was done as three volumes, but the edition I have transcribed put all

three volumes together as a clothbound book. As a result it had three

identical prefaces and duplicated ads. I have included one preface, at

the beginning, and put the ads at the end of the book. I have rotated a

couple of illustrations.

Arts and Science Series No. 7

Home-made

Electrical Apparatus

A Practical Handbook for Amateur

Experimenters

In Three Parts

*Volume I*

_Second Edition_

*BY*

*A. M. Powell*

PUBLISHED BY

COLE & MORGAN, Inc.

Publishers of the Arts and Science Series

P.O. BOX 473 CITY HALL STATION

NEW YORK, N. Y.

Printed in U. S. A.

Copyright 1918

by

COLE & MORGAN, Inc.

PREFACE

The purpose of this book is to aid the young experimenter in building

and operating his own electrical apparatus and instruments. Every boy of

now-a-days experiments with electricity and the right sort of book which

furnishes him with ideas gets close to his heart. Of books upon

electricity there is no end. That is granted. But there are very few

_practical_ books for the young experimenter who wishes to construct

miscellaneous electrical apparatus for his own amusement and instruction

which really amounts to something and which is worth his pains when the

labor has been finished.

This book is therefore offered as a volume of instruction for making all

sorts of batteries, rectifiers, motors, etc., which are entirely out of

the toy class and yet are not so elaborate that they cannot be easily

constructed _at home_ by the average boy who is willing to put a little

care into his work. The materials required are such that they can he

procured without any great expense.

It has been planned to present the material in such a manner that it

will aid the judgment of the young experimenter and assist him in

developing his own ideas. Without exception, all of the apparatus

described in the following pages has been actually constructed by the

author, not only once but many times and put to a practical test before

being embodied into the book. You may therefore be sure that if you

follow the instructions carefully, that the result will in each case be

a substantial piece of apparatus which is capable of fulfilling all of

your expectations.

The drawings have all been reproduced on a large scale and in almost

every case the dimensions of even the smallest details have been given.

Some of the apparatus has been described in the pages of the "Boys’

Magazine" and since its publication the readers of that magazine have

written to the author asking questions about the apparatus which have

enabled him when rewriting the material for publication in book form to

clear up many questions and further explain in a little more detail many

of the problems which naturally occur to the boy who likes to build his

own electrical devices.

THE AUTHOR.

PREFACE ...........................................................

CHAPTER I. STATIC ELECTRICAL APPARATUS ............................

How to Build a Wimshurst Machine. ...............................

Experiments with Static Electrical Apparatus. ...................

CHAPTER II. CELLS AND BATTERIES. ..................................

The Voltaic Cell. ...............................................

Homemade Batteries. .............................................

Battery Solutions or Electrolytes. ..............................

Connecting Cells. ...............................................

Storage or Secondary Cells. .....................................

An Experimental Storage Cell. ...................................

A Homemade Storage Cell. ........................................

Recharging and Caring for Storage Cells. ........................

CHAPTER III. HOW TO REDUCE THE 110 V. D.C. OR A.C. TO A LOWER

VOLTAGE FOR EXPERIMENTAL PURPOSES. ................................

CHAPTER IV. HOW AN ALTERNATING CURRENT MAY BE CHANGED INTO DIRECT

CURRENT BY MEANS OF AN ELECTROLYTIC RECTIFIER. ....................

CHAPTER V. HOW TO BUILD A STEP-DOWN TRANSFORMER FOR REDUCING THE 110

VOLT A. C. FOR EXPERIMENTAL PURPOSES. .............................

CHAPTER VI. ELECTRIC MEASURING INSTRUMENTS ........................

Galvanometers, Ammeters, Voltmeters. How to Make a Galvanometer. .

The Construction of Ammeters and Voltmeters. ....................

CHAPTER VII. CURRENT CONTROL DEVICES. .............................

How to Make a Pole Changing Switch or Current Reverses How to

Reverse a Small Motor. ..........................................

How to Make a Small Battery Rheostat for Regulating the Speed of

Small Motors, Etc. ..............................................

CHAPTER VIII. HOW TO MAKE A TELEGRAPH KEY AND SOUNDER AND INSTALL A

TELEGRAPH LINE. ...................................................

CHAPTER IX. HOW TO MAKE AND INSTALL A TELEPHONE. ..................

CHAPTER X. MEDICAL COILS AND SHOCKING COILS. ......................

CHAPTER XI. THE CONSTRUCTION OF SPARK COILS. ......................

Experiment 1—An Imitation Gassiot’s Cascade. ....................

Experiment 2—A Ghostly Light ....................................

Experiment 3—Lighting Geissler Tubes. ...........................

Experiment 4—Flickering Light. ..................................

Experiment 5—Rotating a Geissler Tube. ..........................

Experiment 6—Fluorescent Writing. ...............................

Experiment 7—An Electric Bomb. ..................................

Experiment 8—Electrifying the Garbage Can. ......................

Experiment 9—How to Make an Electric Spark Photograph Itself. ...

CHAPTER XII. HOW TO MAKE A DYNAMO-MOTOR ...........................

CHAPTER XIII. AN ELECTRIC BATTERY MOTOR. ..........................

CHAPTER XIV. HOW TO BUILD AN ELECTRIC ENGINE. .....................

CHAPTER XV. MINIATURE BATTERY LIGHTING. ...........................

CHAPTER XVI. COHERER OUTFITS FOR WIRELESS TELEGRAPHY. .............

CHAPTER XVII. HOW TO BUILD A TESLA HIGH FREQUENCY COIL. ...........

CHAPTER XVIII. AN EXPERIMENTAL WIRELESS TELEPHONE. ................

CHAPTER XIX. MISCELLANEOUS EXPERIMENTS AND APPARATUS. .............

ELECTROLYSIS. ...................................................

ELECTROPLATING. .................................................

ELECTRIC CURRENT GENERATED BY HEAT. .............................

A HANDY LIGHT. ..................................................

AN EXPERIMENTAL ARC LAMP. .......................................

A MAGNETIC DIVER. ...............................................

THE MAGNETIC FISH. ..............................................

A MAGNETIC CLOWN. ...............................................

AN ELECTRIC BREEZE. .............................................

A STATIC MOTOR. .................................................

FIG. 1.—A simple Wimshurst Machine which any boy can easily make. P

P, Plates; BR, Neutralizes; C R, Collectors; DR, Discharge Rods; J

J, Leyden Jars; H H, Insulating Handles; C, Crank; U, Upright; B,

Belt. .............................................................

FIG. 2.—The plates for the Static Machine are made of hard rubber

and are 7 inches in diameter. Each plate carries sixteen tinfoil

sectors. ..........................................................

FIG. 3.—The details of the Tinfoil Sector. Sixteen are required for

each plate. They are stuck to the plates with shellac. ............

FIG. 4.—Details of the Grooved Pulley, attached to each plate. The

Pulleys are turned out of wood. ...................................

FIG. 5.—The base of the Wimshurst Machine. All woodwork about the

machine should be carefully dried and then shellaced so that it

cannot absorb any moisture. .......................................

FIG. 6.—Details of one of the Uprights which support the Plates,

Driving Pulleys, etc. These, being made of wood, should also be

dried and shellaced so that they cannot absorb moisture. ..........

FIG. 7.—Showing the Two Uprights in position on the Base. .........

FIG. 8.—The Driving Pulleys. These are turned out of wood and

mounted on a shaft having a Crank at one end. .....................

FIG. 9.—The Crank is bent out of a piece of 3/16 rod, 7 inches long,

into the shape shown. .............................................

FIG. 10.—The Collector with the Discharge Rods, etc, in position. A

is the Brass Ball forming one terminal of the gap across which the

sparks jump. B is another Brass Ball screwed onto the end of the

Collector Rod and having a hole in it, through which the Discharge

Rod slips. CC are two threaded Washers used to clamp the Discharge

Rod in place. .....................................................

FIG. 11.—Showing how Binding Posts may be substituted for Round

Balls on the Collector Rods. ......................................

FIG. 12.—Details of the Discharger Rods. ..........................

FIG. 13.—The Supporting Bar upon which the Collector Rods are

mounted. Made of hard rubber so as to be a perfect Insulator. .....

FIG. 14.—The Neutralizers. Two are required. They are bent out of

Brass Rod and fitted with a Tinsel Tuft at each end. The centre

piece upon which the Rod is mounted should be of Hard Rubber. ....

FIG. 15.—Details of the Leyden Jars. They are simply small Test

Tubes, coated inside and outside with tinfoil for about two-thirds

their height and fitted with a Brass Rod connected with the inside

coating. ..........................................................

FIG. 16.—A Large Leyden Jar for experimental purposes. ............

FIG. 17.—Showing how to Discharge a Leyden Jar with a curved piece

of stiff wire fitted to a Wooden Handle. ..........................

FIG. 18.—The "Lightning Board" is simply a Strip of Glass covered

with small Tinfoil Squares. It may be insulated by mounting on a

Bottle. The two Wires attached to the wide Tinfoil Strips at the

ends of the "Board" are for connection to the Static Machine or

Leyden Jar. .......................................................

FIG. 19.—A very pretty effect can be produced by arranging small

tinfoil strips on the Glass in a Pattern. Each strip should be

separated from the other just far enough for a Spark to pass. .....

FIG. 20.—A very pretty design made by arranging the Strips in the

form of a Seven-pointed Star. Flowers, initials or almost any

pattern may be made in the same way. ..............................

FIG. 21.—The Electric Parasol. The upper right-hand corner shows a

piece of Tissue Paper cut into Strips. (1) Is the apparatus before

the Tissue Paper is fastened to the Cork. (2) Shows the completed

"Parasol" and (3), the Parasol when connected to the machine and the

latter is set in operation. .......................................

FIG. 22.—Electric Birds. The Birds are made of Tissue Paper and

should be about the size and shape shown in the lower right-hand

corner of the illustration above. .................................

FIG. 23.—Electric Acrobats. The Acrobats are made of paper. The

little figure in the upper right-hand part of the illustration is

the proper size. ..................................................

FIG. 24.—The Electric Mortar. C is the Mortar, P the Powder, B a

Small Ball and W W the two Wires between which the Spark igniting

the powder takes place. ...........................................

FIG. 25.—An Electric Whirligig. ...................................

FIG. 26.—A Voltaic Cell. A Voltaic Cell consists of a Strip of

Copper and a Strip of Zinc immersed in a dilute solution of

Sulphuric Acid. ...................................................

FIG. 27.—Ordinary Jelly Glasses, Tumblers, Fruit Jars, etc, make

good Jars for small cells by cutting off the tops. ................

FIG. 28.—A Simple Home-made Cell. .................................

FIG. 29.—A Home-made Battery having two Carbon Plates with a Zinc

Rod between. ......................................................

FIG. 30.—The Elements for a Simple Home-made Cell composed of two

Carbon Rods and one Zinc Rod clamped between two Wooden Strips. ...

FIG. 31.—Four Carbon Rods and one Zinc Rod arranged to form the

Elements of a Cell. ...............................................

FIG. 32.—A Battery of Three Cells arranged so that they can all be

lifted out of the solution at once. ...............................

FIG. 33.—Showing how Cells are arranged when they are connected in

Series. The Voltage of Six Dry Cells connected in series as above

would be approximately 6 x 1.5 or 9 Volts. ........................

FIG. 34.—Showing Six Dry Cells connected in Multiple. The Voltage of

such an arrangement would only be 1.5, but the Amperage available

would be six times that possible from Cells connected as in Figure

33. ...............................................................

FIG. 35.—Showing how to connect a Battery of Cells in

Series-Multiple. ..................................................

FIG. 36.—Battery Connectors like that shown above can be obtained

for 1 1/2 cents each and will be found to be very handy. ..........

FIG. 37.—A Simple Experimental Storage Battery consisting of two

Lead Plates immersed in Dilute Sulphuric Acid. ....................

FIG. 38.—Showing how to charge a Simple Storage Cell composed of two

Lead Plates immersed in Sulphuric Acid by connecting it to two

Bichromate of Potash Cells. .......................................

FIG. 39.—Showing how the Plates for a Storage Cell may be made from

Sheet Lead by boring it full of holes and filling with paste. .....

FIG. 40.—A set of three Plates composed of One Positive and Three

Negatives assembled to form a Cell. ...............................

FIG. 41.—Glass and Rubber Storage Cell Jars which are on the market

for the Electrical Experimenter and may be purchased very

reasonably. .......................................................

FIG. 42.—An empty Storage Cell Grid and also a Pasted Plate both of

which are on the market for experimenters who wish to build their

own Cells. ........................................................

FIG. 43.—Two Negative Plates "burned" together and the Connecting

Lug used. .........................................................

FIG. 44.—The Elements of a Storage Cell composed of two Negative

Plates and one Positive Plate in their proper position. ...........

FIG. 45.—Three different sizes of Storage Cells which may be

purchased ready made or built by the experimenter out of prepared

materials as explained. ...........................................

FIG. 46.—A Hydrometer for preparing and testing the Acid Solution

for Storage Batteries. ............................................

FIG. 47.—The proper way of Recharging Storage Cells from the 110

Volts D. C. Supply in series with a set of Lamps. .................

FIG. 48.—A Lamp Bank consisting of a Set of 110-Volt Lamps connected

Multiple and arranged to be placed in series with any device it is

desired to use on the 110-Volt Current. ...........................

FIG. 49.—A Single Cell of Electrolytic Rectifier. .................

FIG. 50.—An Electrode cut out of Sheet Metal. The top is bent over

at right angles and drilled so that it can be mounted on the

underside of the cover. ...........................................

FIG 51.—A Cast Electrode will last much longer than one cut from

Sheet Metal. Cast Electrodes like that above are on the market and

can be purchased very reasonably. .................................

FIG. 52.—A completed single Cell Rectifier. The right hand sketch

shows how the Electrodes are mounted on the underside of the cover.

FIG. 53.—A Diagram showing how a Rectifier cuts off one-half of the

Alternating Current Wave and changes it into Pulsating Direct

Current. ..........................................................

FIG. 54.—Circuit showing how a Single Cell of Rectifier should be

connected in series with a Lamp Bank to Recharge a Storage Cell. A

is the Aluminum Plate and L the Lead or Iron Plate. ...............

FIG. 55.—Diagram showing the Difference in Current after it has been

passed through a Single Cell or Rectifier and after passing through

a Four-Cell Rectifier. ............................................

FIG. 56.—Diagram showing how a Four-Cell Rectifier is connected. The

Alternating Current Source is connected to C and D. The Direct

Current is taken off at A and B. The Electrodes marked A, A, A, A

are the Aluminum Electrodes. L, L, L, L may be Lead or Iron. ......

FIG. 57—A Complete Four-Cell Rectifier connected together and

Mounted in a Tray. ................................................

FIG. 58.—Details of the two different Pieces of Sheet Iron used in

building up the Core. Sufficient of each piece are required to form

a pile of each three-quarters of an inch thick. ...................

FIG. 59.—The Method used in piling up the Strips to Assemble the

Core. .............................................................

FIG. 60.—Assembly of the Core. ....................................

FIG. 61.—Details of the Primary and Secondary Windings. ...........

FIG. 62.—Showing the Core completely assembled with the Primary and

Secondary in position. P, P are the Primary Terminals. 1, 2 and 3

are the Secondary Terminals. ......................................

FIG. 63.—The Step-down Transformer mounted on a Wooden Base. ......

FIG. 64.—A detailed Drawing showing how the Sides of the Case are

formed by bending a long strip of Sheet Iron at four points. ......

FIG. 65.—Details of the Top and Bottom of the Case. ...............

FIG. 66.—The completed Transformer. ...............................

FIG. 67.—A Simple Galvanometer. ...................................

FIG. 68.—Details of the Bobbin. ...................................

FIG. 69.—Details of the Armature, Bearings and Pointer. ...........

FIG. 70.—A complete Voltmeter having the Scale at the top. ........

FIG. 71—An Ammeter so constructed that the Scale is at the bottom. .

FIG. 72.—Showing how the Armature, Shaft and Pointer are assembled

for a Meter having the Scale at the bottom. .......................

FIG. 73.—Details of the Wooden Parts which form the Case. .........

FIG. 74.—Showing how the Apparatus is arranged and connected for

calibrating the Ammeter. ..........................................

FIG. 75.—Showing how the Apparatus is arranged and connected for

calibrating the Voltmeter. ........................................

FIG. 76.—A Pole changing Switch for reversing Small Motors or the

direction of an Electric Current. .................................

FIG. 77.—Top view of a small Battery Rheostat .....................

FIG. 78.—Details of the Rheostat Base. The lower part of the

illustration is a cross section. ..................................

FIG. 79.—Looking at the Base from the bottom showing the grooves in

which the Wires are laid. .........................................

FIG. 80.—The German-silver Resistance Wire is wound around a Fibre

Strip. ............................................................

FIG. 81.—The Lever, Knob, Binding Posts, etc. .....................

FIG. 82.—The completed Rheostat. ..................................

FIG. 83.—Key Frame. ...............................................

FIG. 84.—Sounder Frame. ...........................................

FIG. 85.—The Electro Magnets. .....................................

FIG. 86—The Sounder Armature. .....................................

FIG. 87.—Sounder Frame with Lever in Position. ....................

FIG. 88.—Top View of Completed Instrument .........................

FIG. 89.—Side View of Key. ........................................

FIG. 90.—Key and Circuit Closing Levers. ..........................

FIG. 91.—American Morse Code. .....................................

FIG. 92.—Circuit for Two Instruments. .............................

FIG. 93.—The Wooden Back for the Telephone. .......................

FIG. 94.—The Complete Telephone. ..................................

FIG. 95.—Details of the Receiver Hook. ............................

FIG. 96.—Showing how the Push Button is arranged. .................

FIG. 97.—Circuit showing how to connect two Telephone Stations to

the Line. .........................................................

FIG. 98.—Bobbin for Medical Coil. .................................

FIG. 99.—Bobbin with Winding. .....................................

FIG. 100.—Construction of the Core. ...............................

FIG. 101.—Vibrator Parts and Core Cap. ............................

FIG. 102.—Regulator Tube. .........................................

FIG. 103.—The Base with Location of Holes. ........................

FIG. 104.—Top View of Finished Coil. ..............................

FIG. 105.—Side View of Completed Coil. ............................

FIG. 106.—Vibrator Parts. .........................................

FIGS. 107 and 108.—Two Types of Handles. ..........................

FIG. 109.—Induction or Spark Coil. ................................

FIG. 110.—The Primary and Core. ...................................

FIG. 111.—The Secondary Winding. ..................................

FIG. 112.—The Fixed Condenser. ....................................

FIG. 113.—Details of the Wooden Coil Heads. .......................

FIG. 114.—Details of the Wooden Base. .............................

FIG. 115.—Details of the Interrupter. The Spring and Standard for

the One inch coil should be made one-quarter of an inch longer. ...

FIG. 116.—The tube. ...............................................

FIG. 117.—The Bridge. .............................................

FIG. 118.—Section of the Spark Coil showing the arrangement of the

Parts. ............................................................

FIG. 119.—End View of the Complete Coil. ..........................

FIG. 120.—Side View of the Completed Coil. ........................

FIG. 121.—Diagram of Connections. .................................

FIG. 122.—Perspective view of Coil showing names of the various

parts. ............................................................

FIG. 123—Front view of the Field Casting. .........................

FIG. 124.—Side elevation of the Field Casting. ....................

FIG. 125.—Details of the Armature. ................................

FIG. 126.—The Commutator. .........................................

FIG. 127.—The Armature and Commutator Assembled on the Shaft ready

for winding. ......................................................

FIG. 128.—Details of the Wooden Base. .............................

FIG. 129.—Details of the Bearings. ................................

FIG. 130.—The Pulley. .............................................

FIG. 131.—The Brushes. ............................................

FIG. 132.—The Completed Dynamo. ...................................

FIG. 133.—The completed Electric Motor. ...........................

FIG. 134.—Details of the Field Frame. .............................

FIG. 135.—The Assembled Field ready for Winding. ..................

FIG. 136.—Details of the Armature Lamination. .....................

FIG. 137.—The Armature assembled on the Shaft ready to Wind. ......

FIG. 138.—The Commutator. .........................................

FIG. 139.—Diagram showing how the Armature Coils are connected to

the Commutator Sections. ..........................................

FIG. 140.—The Bearings. ...........................................

FIG. 141.—The Brushes. ............................................

FIG. 142.—The Fibre Block for supporting each Brush. ..............

FIG. 143.—Completed Electric Engine. ..............................

FIG. 144.—The Engine Base. ........................................

FIG. 145.—Details of the Electromagnet Bobbin. ....................

FIG. 146.—Details of the Engine Frame. ............................

FIG. 147—The Bearings. ............................................

FIG. 148.—Details of the Shaft. ...................................

FIG. 149.—The Armature, Armature Bearing and Connecting Rod. ......

FIG. 150.—The Brushes. ............................................

FIG. 151.—A Flywheel may be cut from sheet iron. ..................

FIG. 152.—Small Tungsten Battery Lamps. ...........................

FIG. 153.—A Simple Lighting Arrangement. ..........................

FIG. 154.—Showing the differences between the Candelabra, Single

Ediswan and Double Ediswan Types of Lamp Bases. ...................

FIG. 155.—Miniature Sockets of the types known as "Flat Base

Porcelain," "Pin" and "Weatherproof." .............................

FIG. 156.—Connections for a 2.8 Volt Lamp. ........................

FIG. 157.—A Miniature Base Tungsten Filament Battery Lamp for small

lighting. .........................................................

FIG. 158.—A Tungsten Automobile Lamp with Ediswan Base. ...........

FIG. 159.—Lamps Controlled by One Switch. .........................

FIG. 160.—Lamps Controlled by Separate switches. ..................

FIG. 161.—Double Control System. ..................................

FIG. 162.—The Coherer Details. ....................................

FIG. 163.—The Complete Coherer. ...................................

FIG. 164.—Pony Type Relay. ........................................

FIG. 165.—Connections for the Receiving Set. ......................

FIG. 166.—Coherer, Decoherer and Relay Connections. ...............

FIG. 167.—How the Transmitter is Connected. .......................

FIG. 168.—The Complete Spark Gap. .................................

FIG. 169.—Details of Spark Gap. ...................................

FIG. 170.—Tesla Coil Circuits. ....................................

FIG. 171.—Secondary Tube. .........................................

FIG. 172.—Details of the Secondary Heads. .........................

FIG. 173.—Details of the Primary Head. ............................

FIG. 174.—Primary Cross Bar. ......................................

FIG. 175.—Front View of the completed Tesla Coil. .................

FIG. 176—Side View of the completed Tesla Coil. ...................

FIG. 177.—Diagram of connections for operating the Coil. ..........

FIG. 178.—Plate Glass Condenser. ..................................

FIG. 179.—When a Bar Magnet is plunged into a Hollow Coil of Wire, a

Momentary Current of Electricity is Generated. ....................

FIG. 180.—Magnetic Phantom showing the Lines of Force about a Bar

Magnet. ...........................................................

FIG. 181.—Magnetic Phantom about a Coil of Wire carrying a current.

FIG. 182.—Illustrating the Principle of the Induction Wireless

Telephone. ........................................................

FIG. 183.—Showing how the Coils may be formed by winding around

nails set in a circle in the Floor. ...............................

FIG. 184.—Circuit Diagram showing how the Coil is connected so as to

serve for either transmitting or receiving. .......................

FIG. 185.—Apparatus for Electrolysis Experiment. ..................

FIG. 186.—Electroplating Tank. ....................................

FIG. 187.—Generating Electric Current by Heat. ....................

FIG. 188.—A Handy Light. ..........................................

FIG. 189.—Experimental Arc Lamp. ..................................

FIG. 190.—The Magnetic Diver. .....................................

FIG. 191.—The Magnetic Fish. ......................................

FIG. 192.—The Magnetic Clown. .....................................

FIG. 193.—An Electric Breeze. .....................................

FIG. 194.—The Static Motor. .......................................

CHAPTER I. STATIC ELECTRICAL APPARATUS

*Static Electricity. How to Build a Wimshurst Machine. Experiments with

Static Electrical Apparatus.*

*Static Electricity* is an extremely interesting subject for the amateur

experimenter, in view of the many spectacular experiments which may be

performed with it. The number of such experiments is almost unlimited.

Static electricity was the first evidence of the wonderful force which

in the present day moves trains, lights our homes, etc., to come to the

notice of man. Long before the days of batteries, dynamos, telegraphs,

electric lights and before, perhaps, such things were even dreamed of,

static electricity absorbed the attention of scientists, and the names

of some of the world’s greatest men such as for instance, Aristotle,

Roger Bacon, Gilbert, Boyle, Newton, Franklin, etc., are closely linked

with its history. It is probably safe to say that experiments with

static electricity led the famous Italian, Galvani, to the discovery of

the sort of electricity called *galvanic* currents, and to the battery.

Galvanic current is the sort of electricity produced by batteries and

has the same properties in many ways as that generated by huge dynamos

in the power houses of to-day.

The modern boy can duplicate these old experiments far more easily and

on a larger scale than any of the old scientists could, owing to the

fact that he is supplied with explicit directions and can easily obtain

the necessary materials at a neighboring hardware or electrical store,

whereas men like Newton and Franklin not only had to *devise* or

*invent* their own apparatus but make their materials as well.

How to Build a Wimshurst Machine.

Static electricity and lightning are the same thing.

A boy can produce static electricity in small quantities by rubbing a

glass rod with a piece of flannel or silk.

[Illustration: FIG. 1.—A simple Wimshurst Machine which any boy can

easily make. P P, Plates; BR, Neutralizes; C R, Collectors; DR,

Discharge Rods; J J, Leyden Jars; H H, Insulating Handles; C, Crank; U,

Upright; B, Belt.]

Rub the rod briskly and then hold it over some tiny bits of paper or

specks of dust and watch them jump up to meet the rod, just as if the

latter were a magnet attracting small tacks or nails. It is static

electricity which gives the rod this wonderful power. If you rub the rod

briskly and then hold it close to your cheek, you will feel a slight

tickling and hear a faint crackling sound. If this is done in the dark

you may be able to see a very faint phosphorescent light or even small

sparks.

The quantity of electricity produced in this manner by rubbing a glass

rod is extremely limited and while a number of very interesting and

instructive experiments may be performed in this manner, the most

spectacular ones are only possible with the aid of a "static-machine".

[Illustration: FIG. 2.—The plates for the Static Machine are made of

hard rubber and are 7 inches in diameter. Each plate carries sixteen

tinfoil sectors.]

The most practical form of static machine is that known as the

"Wimshurst". It consists of two circular plates made of glass or hard

rubber arranged so that by turning a crank, they may be revolved in

opposite directions. On these plates are a number of small strips of

tinfoil. The static electricity is generated on these tinfoil strips and

collected by two metal rods having small pins arranged along them in a

row.

A simple form of Wimshurst machine which any boy can easily make is

illustrated in Figure 1. It will generate considerable static

electricity and will make sparks two inches long.

*The Plates* on these machines are hard rubber. They are illustrated in

Figure 2. Glass is usually used for static machine plates, but has the

disadvantage of breaking easily. It is also hard for the young

experimenter to cut out circular glass plates and drill them. The author

has had very good success with hard rubber.

[Illustration: FIG. 3.—The details of the Tinfoil Sector. Sixteen are

required for each plate. They are stuck to the plates with shellac.]

Two plates are required for the machine. They should be in the form of

circles seven inches in diameter and be perfectly true. They need to be

only one-sixteenth of an inch thick. The rubber should be perfectly flat

and not warped at any point.

*The Sectors*, as the tinfoil strips are called, are wedge shaped pieces

having rounded ends as shown in Figure 3. They should be cut of heavy

tinfoil. Thirty-two sectors are required, sixteen for each plate. They

are seven-sixteenths of an inch wide at the top, one inch long and

five-sixteenth of an inch wide at the bottom.

The plates should be very carefully cleaned by rubbing with a dry cloth

and then laid on a flat surface all ready to receive the sectors.

The sectors should be stuck to the plates with thick shellac. They

should be arranged all on one face, symmetrically and at equal distances

apart, with the inner ends resting on a circle four and one-half inches

in diameter. Each sector should be carefully pressed down on the rubber

so that it sticks smoothly without any air bubbles or creases.

Both plates should be treated in the same manner.

[Illustration: FIG. 4.—Details of the Grooved Pulley, attached to each

plate. The Pulleys are turned out of wood.]

*The Pulley* illustrated in Figure 4 is one inch in diameter and

eleven-sixteenths of an inch thick. Two of these pulleys will be

required. The hole through the centre should be about three-sixteenths

of an inch in diameter. One pulley should be attached to each of the

rubber plates. The large face of the pulley should be against the face

of the plate upon which the tinfoil sectors are mounted. The hole in the

centre of the pulley should line up perfectly with a hole of the same

size in the centre of each one of the plates. The plates are fastened to

the pulleys by three small brass nails driven into the wood through

small holes in the rubber.

*The Base* of the machine is a rectangular shaped piece of wood six

inches long, four inches wide and three-quarters of an inch thick. A

notch, one inch wide and one-half an inch deep is cut in the centre of

the front and back as shown in Figure 5. The purpose of these notches is

to receive the uprights.

*The Uprights* are strips of wood, seven inches long, one inch wide and

one-half an inch thick. The tipper end of each of the uprights is

rounded as shown in Figure 6.

[Illustration: FIG. 5.—The base of the Wimshurst Machine. All woodwork

about the machine should be carefully dried and then shellaced so that

it cannot absorb any moisture.]

Two holes should be bored through each of the uprights from front to

back. The lower hole is three-sixteenths of an inch in diameter and two

and one-quarter inches from the bottom. The upper hole is six and

one-half inches from the bottom and is between one-eighth and

three-sixteenths of an inch in diameter so that a three-sixteenth rod

driven into it will fit tightly.

The uprights should be mounted in position in the base and fastened with

screws.

The plates are mounted between the upper ends of the uprights in the

position shown in Figure 1, by driving a short piece of 3/16 round brass

rod through the uprights into the holes in the centre of the pulleys.

The rod used to mount the back plate should be one and one-half inches

long and that used for the front plate one and five-eighths inches long.

The 3/16 hole in the pulleys should be large enough so that the latter

will revolve freely.

The plates are revolved by two driving pulleys provided with a crank for

turning.

*The Driving Pulleys* are shown in Figure 8. They are not so easy to

make as the small pulleys attached to the plates. They are turned out of

wood and should be both alike. The exact shape and dimensions are shown

in the illustration. The hole through the centre should be a scant

three-sixteenths of an inch so that the pulleys will force onto a 3/16

rod very tightly.

*The Crank* is bent out of a piece of brass or steel rod about seven

inches long. The straight portion, forming the shaft upon which the

pulleys are mounted, is three and seven-eighths inches long. The portion

at right angles to this, forming what is known as the "throw" of the

crank, is one inch and seven-eighths. The part forming the crank handle

is one inch and one-quarter long.

[Illustration: FIG. 6.—Details of one of the Uprights which support the

Plates, Driving Pulleys, etc. These, being made of wood, should also be

dried and shellaced so that they cannot absorb moisture.]

The driving pulleys are placed between the two standards with the small

projecting portions or "bosses" nearest the uprights. The straight

portion of the crank should then be slipped through the hole in the

front upright and driven tightly into the driving pulleys. The driving

pulleys should fit so tightly onto the shaft that they will not slip.

The end of the shaft should project through the pulleys far enough so

that is rests in the hole in the rear standard.

The holes in the uprights or standards should be just large enough so

that the shaft will turn freely. The driving pulleys should be lined up

so that the groove in each comes directly under the groove in the

corresponding pulley attached to the plate above.

*The Belts* consist simply of heavy cotton cord. The rear belt should be

crossed so that the rear plate runs in the opposite direction from the

front plate when the crank is turned.

The electricity is collected from the sectors on the plates by two

*Collectors.* These are illustrated in Figure 10 and consists of a piece

of 5/32 brass rod, about six inches long, bent into the shape shown. Two

small tufts of "tinsel" are soldered to the U-shaped portion of the

collector so that when the latter is placed in its proper position on

the machine, they will brush against the tinfoil-sectors as they pass

when the plates revolve.

[Illustration: FIG. 7.—Showing the Two Uprights in position on the

Base.]

The other end of the rod is threaded to fit into a hole in a small brass

ball about three-eighths or one-half inch in diameter. Many

experimenters may have difficulty in securing a suitable brass ball for

this purpose. An ordinary binding post may be used instead. The hole in

the bottom of a binding post is usually threaded to fit an 8-32 screw.

The end of the rod is just the right size to receive an 8-32 thread and

so there should be no trouble in getting the parts to fit. The brass

ball is marked "A" in the illustration. The ball is preferable to the

binding because it has no sharp corners from which the electricity might

leak. Static electricity leaks from sharp edges or corners and they must

always be avoided as far as possible in the construction of static

apparatus.

The end of the rod where it screws into the ball or binding post should

be threaded back for a distance of about three-quarters of an inch and

two brass nuts screwed onto the rod. These nuts are marked "C" in the

illustration.

[Illustration: FIG. 8.—The Driving Pulleys. These are turned out of wood

and mounted on a shaft having a Crank at one end.]

The collectors are held in position by the supporting bar illustrated in

Figure 13. This bar is made of a strip of hard rubber, five and one

quarter inches long, five-eighths of an inch wide and three-sixteenths

of an inch thick.

Three holes, each five-thirty-seconds of an inch in diameter, should be

bored in the bar. One hole should be exactly in the centre and the other

holes seven-sixteenths of an inch back from the end.

The centre hole is slipped over the end of the shaft which projects

through the front standard supporting the plate and the bar fastened

across the support at right angles like a cross by driving in two small

brass nails or screws through holes made in the rubber for that purpose.

The threaded portion of the collector rods should be slipped through the

holes near the ends of the hard rubber bar and clamped firmly in

position by placing one of the nuts "C" on the back and the other on the

front and tightening them up.

The exact position of the collectors is best understood from Figure 1.

They are lettered C R in the illustration. The brass balls B are screwed

onto the ends of the rods after the nuts have been tightened. Each of

these balls should have a hole, one-eighth of an inch in diameter

drilled through it at right angles to the collector rod. The hole

provided in the binding post for the accommodation of the wire may be

used in case binding posts are employed instead of the rods.

These holes are to accommodate the Discharge Rods, which are two round

brass rods, one-eighth of an inch in diameter and three and one-half

inches long. One end of each of the rods is fitted with a small brass

ball.

[Illustration: FIG. 9.—The Crank is bent out of a piece of 3/16 rod, 7

inches long, into the shape shown.]

The other end of each is provided with a small insulating handle. A No.

8003 Electrose Knob is just the thing. These knobs are provided with a

threaded bushing so that they may be screwed onto the rod.

The proper position for the discharge rods is shown in Figure 1. By

sliding the rods back and forth in the balls on the ends of the

collectors, the distance between the balls on the ends of the rods may

be varied.

The spark discharge from the machine, when the latter is completed,

takes place between these balls.

The machine still remains to be fitted with the "neutralizers" and a set

of Leyden jars.

*The Neutralizers* are illustrated in Figure 14. Two are required. They

consist of a piece of one-eighth inch brass rod, six inches long, having

the ends bent over at right angles so as to form a shallow U. The

distance between the ends when bent should be about three and

five-eights inches. A tuft of tinsel should be soldered to the ends of

each of the neutralizers.

[Illustration: FIG. 10.—The Collector with the Discharge Rods, etc, in

position. A is the Brass Ball forming one terminal of the gap across

which the sparks jump. B is another Brass Ball screwed onto the end of

the Collector Rod and having a hole in it, through which the Discharge

Rod slips. CC are two threaded Washers used to clamp the Discharge Rod

in place.]

Each neutralizer rod is supported by a hard rubber washer three-quarters

of an inch in diameter and five-sixteenths of an inch thick. In the

centre of the washer a hole should be drilled, which will fit snugly

onto the rods upon which the plates are mounted and revolve. The

neutralizer rod passes through a hole in the upper part of the washer as

shown in the illustration.

Before the neutralizers can be put into position it will be necessary to

pull out the rods which support the plates so that the plates can be

removed. The hard rubber washers supporting the neutralizers are then

slipped over the rods so that one will come between each support and

plate when the latter is put back into position. The rods should be

turned so that the tinsel tufts touch the sectors. The rubber washers

should fit snugly on the rods so that the neutralizer will stay in any

position in which it is placed. The proper position for the front

neutralizer is a little less than half way between vertical and

horizontal as shown in Figure 1. The neutralizer behind the rear plate

should be at right angles to that in front.

[Illustration: FIG. 11.—Showing how Binding Posts may be substituted for

Round Balls on the Collector Rods.]

The machine is now all ready for operation. In order for it to operate

satisfactorily it is necessary for it to be warm and dry. It is,

therefore, a very good idea to thoroughly dry the woodwork and give it a

coat of varnish or shellac so that it cannot absorb any moisture. It may

be necessary to start the machine by rubbing a glass rod with a piece of

flannel or silk and then touching the rod to some of the sectors. The

handle of the machine should be turned from left to right, that is, in

such a direction that the front plate revolves in the same direction as

the hands of a clock.

If the machine is in proper working order a stream of small sparks

should flow between the spark balls on the ends of the discharger rods,

provided they are not over a half inch apart, when the crank is turned.

The spark can be intensified and lengthened by fitting the machine with

two small Leyden jars.

*The Leyden Jars* are made from small test tubes three inches long. The

inside of the tube should be coated with tinfoil to within about one

inch from the top. The outside of the tube should be coated in the same

manner for the same distance. The tinfoil can be secured to the glass

with shellac.

The top of the Leyden jars is closed with an ordinary cork. A piece of

heavy brass wire bent into the form of a hook should pass through the

cork and make connection with the tinfoil on the inside of the tube. One

Leyden Jar should be hung over each of the collector rods by means of

the hook. The tinfoil coatings on the outside of the jars should be

connected together by a piece of wire running across from one tube to

the other.

[Illustration: FIG. 12.—Details of the Discharger Rods.]

The machine is now complete and ready for performing a number of very

interesting experiments.

Experiments with Static Electrical Apparatus.

*A Leyden Jar* is a very simple device for accumulating and storing

static electricity. It consists simply of a wide mouthed jar or bottle

coated with tinfoil part way up on both the outside and the inside in

exactly the same manner as the small test tubes used on the static

machine.

Not all glass jars are suitable for making Leyden Jars. The quality of

the glass varies considerably and some will be found far superior to the

rest.

The glass vessels used by chemists and called "beaker glasses" usually

make excellent Leyden Jars.

It is not very difficult to make a good Leyden Jar. After you have

selected the jar or bottle you wish to use, clean and dry it very

thoroughly. Then give the inside a thorough brushing over with shellac.

Cut a strip of tinfoil which is long enough to go all the way around the

inside of the jar and about two-thirds its height. Before the shellac is

thoroughly dry but is still sticky, insert the tinfoil strip carefully

into the jar and press it smoothly against the glass.

[Illustration: FIG. 13.—The Supporting Bar upon which the Collector Rods

are mounted. Made of hard rubber so as to be a perfect Insulator.]

The outside of the jar should also be given a coat of shellac and

covered with tinfoil in exactly the same manner. The tinfoil on the

outside of the jar should be the same height as that on the inside. The

bottom of the jar should be coated, both inside and out by cutting two

circular pieces out of the tinfoil and sticking them on with shellac.

The jar should be provided with a wooden cover which will fit snugly

into the top. The wood should be dried and then given a coat of shellac

so that it cannot absorb any moisture.

[Illustration: FIG. 14.—The Neutralizers. Two are required. They are

bent out of Brass Rod and fitted with a Tinsel Tuft at each end. The

centre piece upon which the Rod is mounted should be of Hard Rubber.]

It may perhaps be well at this point to emphasize how highly important

it is to always keep all static electrical apparatus thoroughly dry and

to construct it so that it will not collect or absorb any moisture.

A small hole should be bored through the centre of the cover so as to

permit a brass rod to pass through. A piece of spring wire bent into a

spiral should be attached to the lower end of the rod. When the cover is

in position, the spring wire should make contact with the tinfoil on the

inside of the jar.

It is a very good idea to fit the top of the rod with a small brass

ball. This will prevent the electricity from "leaking" from the sharp

corners on the end of the rod. Static electricity leaks very easily from

sharp corners or points, but does not escape so readily from round

corners or balls.

[Illustration: FIG. 15.—Details of the Leyden Jars. They are simply

small Test Tubes, coated inside and outside with tinfoil for about

two-thirds their height and fitted with a Brass Rod connected with the

inside coating.]

The Leyden jar may be "charged" with electricity from the static machine

by connecting a wire from one of the discharge rods to the outside

tinfoil coating on the jar. Another wire should be connected from the

other discharge rod to the rod on the jar which connects with the inside

tinfoil coating.

Turning the handle of the machine rapidly for ten or fifteen seconds

will charge the jar. Disconnect the wires as promptly as possible so

that the electricity in the jar will not have a chance to leak back into

the machine. Be very careful while doing this, however, because if you

should happen to touch the tinfoil on the outside of the jar and the rod

which connects with the inside coating at the same time you will get one

of the surprises of your life.

[Illustration: FIG. 16.—A Large Leyden Jar for experimental purposes.]

The shock won’t really hurt you any but it will be very uncomfortable

and somewhat surprising.

You can discharge a Leyden jar by bringing a piece of wire which is

connected to the outside coating, near to the knob on the rod. When the

wire is close to the ball the electricity will jump across the space in

the shape of a snapping white spark.

The Leyden jar can be used in connection with a number of experiments

described later on.

[Illustration: FIG. 17.—Showing how to Discharge a Leyden Jar with a

curved piece of stiff wire fitted to a Wooden Handle.]

*Bottled Lightning.* A very pretty effect can be obtained by passing the

spark from a Leyden jar or a static machine over a "lightning board." A

"lightning board" consists of a pane of glass having a number of small

squares of tinfoil stuck on it so that when the electrical discharge is

passed over it, sparks take place between the little tinfoil squares and

produce an effect something like miniature lightning.

A lightning board suitable for the static machine just described may be

made from a strip of ordinary window glass about nine inches long and

two inches wide.

Clean the glass thoroughly and then give it a coat of shellac on one

side. As soon as the shellac becomes sticky, lay on a strip of tinfoil

the same size as the glass and rub it down smoothly. When the shellac

has thoroughly dried so that the tinfoil is stuck tightly to the glass,

the board is ready to be cut up into squares. This can be best

accomplished by means of a sharp knife and a ruler. Use care in doing

the work so as not to tear the tinfoil and be sure that the knife cuts

all the way through to the glass. Leave two solid strips of tinfoil at

each end to which to make connections.

[Illustration: FIG. 18.—The "Lightning Board" is simply a Strip of Glass

covered with small Tinfoil Squares. It may be insulated by mounting on a

Bottle. The two Wires attached to the wide Tinfoil Strips at the ends of

the "Board" are for connection to the Static Machine or Leyden Jar.]

The lightning board should be mounted by cementing it in a slot in a

cork in a bottle so that the glass bottle serves as an insulated

support.

If one of the tinfoil strips left solid at the end of the board is

connected to one of the discharge rods on the static machine and the

other end is connected likewise to the other discharge rod innumerable

little sparks will zig-zag between the tinfoil squares when the machine

is set in operation. The effect is quite pretty if the experiment is

performed in a dark room.

The Leyden jar can be charged by the static machine and discharged

through the lightning board. The sparks produced by the Leyden jar will

be much more brilliant than those of the static machine above.

A very pretty effect can be produced by arranging the tinfoil in the

form of a pattern or design as for example that illustrated in Figure

19. A strip of glass about the same size as that used for the lightning

board may be employed. The glass is coated with shellac and as soon as

it becomes sticky, small rectangular pieces of tinfoil arranged in a

zig-zag pattern and having small spaces between them, are stuck in

position. The end pieces are made larger than the other strips so as to

afford means for connecting the wires. The strip should then be

insulated and mounted by cementing it in a slot in the cork of a glass

bottle.

[Illustration: FIG. 19.—A very pretty effect can be produced by

arranging small tinfoil strips on the Glass in a Pattern. Each strip

should be separated from the other just far enough for a Spark to pass.]

The apparatus shown in Figure 20 is made according to the same plan but

the glass in this case is in the form of a square instead of a strip.

The tinfoil strips are arranged in the form of a seven pointed star or

any other pattern which may be desirable. The two large strips A and B

are the ones to which the wires should be connected.

*The Electric Parasol* is illustrated in Figure 21. It is made by

pasting some narrow strips of tissue paper, about three-sixteenths of an

inch wide and three or four inches long, to a small cork which has

previously been covered with tinfoil. The strips can be made most easily

by cutting a small sheet of tissue paper into strips like the teeth of a

comb as shown in the upper right hand corner of Figure 21. The tinfoil

covered cork should be mounted on the upper end of a stiff copper or

brass wire supported in a bottle.

If this wire is then connected to one of the discharge rods on the

static machine and the hand held to the other, the paper strips will

spread out like a parasol or umbrella, as soon as the machine is set in

operation.

[Illustration: FIG. 20.—A very pretty design made by arranging the

Strips in the form of a Seven-pointed Star. Flowers, initials or almost

any pattern may be made in the same way.]

A novel experiment somewhat similar in principle to the "electric

parasol" is that shown in Figure 22.

Three small paper birds about the size of that shown at the right hand

side of the illustration should be cut out of tissue paper and each one

attached to a piece of cotton thread about six inches long. The threads

are then tied to one end of a T-shaped frame bent out of copper wire and

supported on a bottle.

If the wire frame is then connected to one of the discharge rods and the

hand held to the other while the machine is set in operation, the birds

will rise in the air and fly around as far as the threads will let them.

[Illustration: FIG. 21.—The Electric Parasol. The upper right-hand

corner shows a piece of Tissue Paper cut into Strips. (1) Is the

apparatus before the Tissue Paper is fastened to the Cork. (2) Shows the

completed "Parasol" and (3), the Parasol when connected to the machine

and the latter is set in operation.]

*Electric Acrobats.* The apparatus shown in Figure 23 consists of a

circular metal plate about four inches in diameter suspended by a wire

from a wire "T" stuck in a cork in a bottle. Another circular metal

plate of the same size is laid on the table below the other. The

distance between the two plates should be about one inch or an inch and

one-half.

Cut three or four little figures, the same size as that shown in the

upper right hand part of the illustration, out of tissue paper and lay

them on the bottom plate.

[Illustration: FIG. 22.—Electric Birds. The Birds are made of Tissue

Paper and should be about the size and shape shown in the lower

right-hand corner of the illustration above.]

The circular metal plates may be made of sheet tin, copper, brass or

galvanized iron. Even cardboard, provided that it is covered with

tinfoil, will serve.

The upper plate should be connected to one discharge rod on the static

machine and the lower plate to the other. Then as soon as the machine is

set in operation the little paper figures will begin to dance up and

down, stand on their heads, hang by one foot or hand, turn somersaults

and perform all sorts of stunts.

*Gunpowder* may be ignited by the spark from a Leyden jar. A miniature

mortar may be made from a piece of broom handle about an inch and

one-half in diameter with a hole one inch deep in one end as shown by C

Figure 24. The mortar should be fastened to a small wooden base which

will support it in an inclined position as in the illustration.

[Illustration: FIG. 23.—Electric Acrobats. The Acrobats are made of

paper. The little figure in the upper right-hand part of the

illustration is the proper size.]

Bore two small holes through the wall of the mortar, near the bottom and

exactly opposite to each other Insert two short pieces of coper wire, W,

W, in the holes and fasten them tightly in position. The ends of the

wires should be about one-eighth of an inch apart.

A small pinch of gunpowder is then placed in the bottom of the mortar.

Charge the Leyden jar and then discharge it through the mortar by

connecting it to the two wires W, W. As soon as the spark passes, the

powder will explode. An experiment such as this should be performed

cautiously and the face and hands should be kept away from the powder.

Do not put more than a pinch of powder in the mortar at a time and by

all means keep the reserve supply out of the way so that there will be

no danger of exploding it by accident.

*An Electric Whirligig* is an interesting piece of apparatus which may

be built by following the suggestions contained in Figure 25.

[Illustration: FIG. 24.—The Electric Mortar. C is the Mortar, P the

Powder, B a Small Ball and W W the two Wires between which the Spark

igniting the powder takes place.]

Mount four pieces of dowel about three inches long at the corners of a

wooden base about eight inches long and two inches wide so that they

form four vertical posts as shown by A, B, C, D.

The dowels, as well as the wooden base should be carefully dried and

shellaced so that they will not absorb any moisture.

Stretch two pieces of straight stiff wire between the posts A C and B D,

near the top. The wires should be perfectly straight and level.

The whirligig itself is made by passing a sewing needle through the axis

of a small cork. Four small wires having the ends bent over at right

angles should then be stuck in the cork as shown in the upper left hand

part of Figure 25. All of the wires should point in the same direction.

[Illustration: FIG. 25.—An Electric Whirligig.]

The four wires should all be the same length so that the whirligig is

perfectly balanced. The cork is then covered with tinfoil so that there

will be an electrical connection between the four small wires and the

needle forming the shaft.

The two wires A C and B D are connected together by a wire A B and a

piece of flexible wire led to the Wimshurst machine. The opposite side

of the Wimshurst machine is then grounded or touched with the hand. If

the whirligig is laid on the wires A C and B D as shown in the

illustration and it is perfectly balanced it will commence to revolve

and roll along the wires just as soon as the Wimshurst machine is set in

operation. It is the escape of the electricity from the points of the

four wires on the whirligig which causes this.

Other interesting experiments in static electricity may be performed

with the aid of a Wimshurst machine and the experimenter who is

sufficiently interested to continue farther is referred to any good book

on physics or some such volume as "The Boy Electrician".