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THE ECONOMY
OF
WORKSHOP MANIPULATION.
THE ECONOMY
OF
WORKSHOP MANIPULATION.
_A LOGICAL METHOD OF LEARNING CONSTRUCTIVE
MECHANICS._
ARRANGED WITH QUESTIONS
FOR THE USE OF
APPRENTICE ENGINEERS AND STUDENTS.
BY
J. RICHARDS,
AUTHOR OF "A TREATISE ON THE CONSTRUCTION AND OPERATION OF
WOOD-WORKING MACHINES," "THE OPERATOR'S HANDBOOK," "WOOD
CONVERSION BY MACHINERY," AND OTHER WRITINGS ON MECHANICAL
SUBJECTS.
LONDON:
E. & F. N. SPON, 48 CHARING CROSS.
NEW YORK: 446 BROOME STREET.
1876.
[_All rights reserved._]
_Entered, according to Act of Congress, in the year 1875, by
JOHN RICHARDS,
In the Office of the Librarian of Congress, at Washington._
PREFACE.
The contents of the present work, except the Introduction and the
chapter on Gauges, consist mainly in a revision of a series of
articles published in "Engineering" and the Journal of the Franklin
Institute, under the head of "The Principles of Shop Manipulation,"
during 1873 and 1874.
The articles alluded to were suggested by observations made in
actual practice, and by noting a "habit of thought" common among
learners, which did not seem to accord with the purely scientific
manner in which mechanical subjects are now so constantly treated.
The favourable reception which the articles on "Shop Manipulation"
met with during their serial publication, and various requests for
their reproduction in the form of a book, has led to the present
edition.
The addition of a few questions at the end of each chapter, some
of which are not answered in the text, it is thought will assist
the main object of the work, which is to promote a habit of logical
investigation on the part of learners.
It will be proper to mention here, what will be more fully pointed
out in the Introduction, that although workshop processes may
be scientifically explained and proved, they must nevertheless
be learned logically. This view, it is hoped, will not lead to
anything in the book being construed as a disparagement of the
importance of theoretical studies.
Success in Technical Training, as in other kinds of education,
must depend greatly upon how well the general mode of thought
among learners is understood and followed; and if the present work
directs some attention to this matter it will not fail to add
something to those influences which tend to build up our industrial
interests.
J. R.
10 JOHN STREET, ADELPHI,
LONDON, 1875.
CONTENTS.
CHAP. PAGE
INTRODUCTION, 1
I. PLANS OF STUDYING, 6
II. MECHANICAL ENGINEERING, 13
III. ENGINEERING AS A CALLING, 17
IV. THE CONDITIONS OF APPRENTICESHIP, 18
V. THE OBJECT OF MECHANICAL INDUSTRY, 25
VI. ON THE NATURE AND OBJECTS OF MACHINERY, 28
VII. MOTIVE MACHINERY, 29
VIII. WATER POWER, 35
IX. WIND POWER, 41
X. MACHINERY FOR TRANSMITTING AND DISTRIBUTING POWER, 42
XI. SHAFTS FOR TRANSMITTING POWER, 44
XII. BELTS FOR TRANSMITTING POWER, 48
XIII. GEARING AS A MEANS OF TRANSMITTING POWER, 51
XIV. HYDRAULIC APPARATUS FOR TRANSMITTING POWER, 53
XV. PNEUMATIC MACHINERY FOR TRANSMITTING POWER, 55
XVI. MACHINERY OF APPLICATION, 57
XVII. MACHINERY FOR MOVING AND HANDLING MATERIAL, 60
XVIII. MACHINE COMBINATION, 67
XIX. THE ARRANGEMENT OF ENGINEERING ESTABLISHMENTS, 71
XX. GENERALISATION OF SHOP PROCESSES, 74
XXI. MECHANICAL DRAWING, 78
XXII. PATTERN MAKING AND CASTING, 90
XXIII. FORGING, 100
XXIV. TRIP-HAMMERS, 106
XXV. CRANK-HAMMERS, 108
XXVI. STEAM-HAMMERS, 109
XXVII. COMPOUND HAMMERS, 112
XXVIII. TEMPERING STEEL, 114
XXIX. FITTING AND FINISHING, 118
XXX. TURNING LATHES, 121
XXXI. PLANING OR RECIPROCATING MACHINES, 128
XXXII. SLOTTING MACHINES, 134
XXXIII. SHAPING MACHINES, 135
XXXIV. BORING AND DRILLING, 136
XXXV. MILLING, 140
XXXVI. SCREW-CUTTING, 143
XXXVII. STANDARD MEASURES, 145
XXXVIII. GAUGING IMPLEMENTS, 147
XXXIX. DESIGNING MACHINES, 152
XL. INVENTION, 159
XLI. WORKSHOP EXPERIENCE, 165
THE ECONOMY
OF
WORKSHOP MANIPULATION.
_INTRODUCTION._
In adding another to the large number of books which treat upon
Mechanics, and especially of that class devoted to what is called
Mechanical Engineering, it will be proper to explain some of the
reasons for preparing the present work; and as these explanations
will constitute a part of the work itself, and be directed to a
subject of some interest to a learner, they are included in the
Introduction.
First I will notice that among our many books upon mechanical
subjects there are none that seem to be directed to the instruction
of apprentice engineers; at least, there are none directed to that
part of a mechanical education most difficult to acquire, a power
of analysing and deducing conclusions from commonplace matters.
Our text-books, such as are available for apprentices, consist
mainly of mathematical formulæ relating to forces, the properties
of material, examples of practice, and so on, but do not deal with
the operation of machines nor with constructive manipulation,
leaving out that most important part of a mechanical education,
which consists in special as distinguished from general knowledge.
The theorems, formulæ, constants, tables, and rules, which are
generally termed the principles of mechanics, are in a sense
only symbols of principles; and it is possible, as many facts
will prove, for a learner to master the theories and symbols of
mechanical principles, and yet not be able to turn such knowledge
to practical account.
A principle in mechanics may be known, and even familiar to a
learner, without being logically understood; it might even be
said that both theory and practice may be learned without the
power to connect and apply the two things. A person may, for
example, understand the geometry of tooth gearing and how to lay
out teeth of the proper form for various kinds of wheels, how to
proportion and arrange the spokes, rims, hubs, and so on; he may
also understand the practical application of wheels as a means of
varying or transmitting motion, but between this knowledge and a
complete wheel lies a long train of intricate processes, such as
pattern-making, moulding, casting, boring, and fitting. Farther
on comes other conditions connected with the operation of wheels,
such as adaptation, wear, noise, accidental strains, with many
other things equally as important, as epicycloidal curves or other
geometrical problems relating to wheels.
Text-books, such as relate to construction, consist generally of
examples, drawings, and explanations of machines, gearing, tools,
and so on; such examples are of use to a learner, no doubt, but in
most cases he can examine the machines themselves, and on entering
a shop is brought at once in contact not only with the machines
but also with their operation. Examples and drawings relate to
_how_ machines are constructed, but when a learner comes to the
actual operation of machines, a new and more interesting problem is
reached in the reasons _why_ they are so constructed.
The difference between _how_ machinery is constructed and _why_
it is so constructed, is a wide one. This difference the reader
should keep in mind, because it is to the second query that the
present work will be mainly addressed. There will be an attempt--an
imperfect one, no doubt, in some cases--to deduce from practice
the causes which have led to certain forms of machines, and to
the ordinary processes of workshop manipulation. In the mind of a
learner, whether apprentice or student, the strongest tendency is
to investigate why certain proportions and arrangement are right
and others wrong--why the operations of a workshop are conducted
in one manner instead of another? This is the natural habit of
thought, and the natural course of inquiry and investigation is
deductive.
Nothing can be more unreasonable than to expect an apprentice
engineer to begin by an inductive course in learning and reasoning
about mechanics. Even if the mind were capable of such a course,
which can not be assumed in so intricate and extensive a subject
as mechanics, there would be a want of interest and an absence
of apparent purpose which would hinder or prevent progress. Any
rational view of the matter, together with as many facts as can be
cited, will all point to the conclusion that apprentices must learn
deductively, and that some practice should accompany or precede
theoretical studies. How dull and objectless it seems to a young
man when he toils through "the sum of the squares of the base and
perpendicular of a right-angle triangle," without knowing a purpose
to which this problem is to be applied; he generally wonders why
such puzzling theorems were ever invented, and what they can have
to do with the practical affairs of life. But if the same learner
were to happen upon a builder squaring a foundation by means of the
rule "six, eight, and ten," and should in this operation detect the
application of that tiresome problem of "the sum of the squares,"
he would at once awake to a new interest in the matter; what was
before tedious and without object, would now appear useful and
interesting. The subject would become fascinating, and the learner
would go on with a new zeal to trace out the connection between
practice and other problems of the kind. Nothing inspires a learner
so much as contact with practice; the natural tendency, as before
said, is to proceed deductively.
A few years ago, or even at the present time, many school-books
in use which treat of mechanics in connection with natural
philosophy are so arranged as to hinder a learner from grasping a
true conception of force, power, and motion; these elements were
confounded with various agents of transmission, such as wheels,
wedges, levers, screws, and so on. A learner was taught to call
these things "mechanical powers," whatever that may mean, and
to compute their power as mechanical elements. In this manner
was fixed in the mind, as many can bear witness, an erroneous
conception of the relations between power and the means for its
transmission; the two things were confounded together, so that
years, and often a lifetime, has not served to get rid of the
idea of power and mechanism being the same. To such teaching can
be traced nearly all the crude ideas of mechanics so often met
with among those well informed in other matters. In the great
change from empirical rules to proved constants, from special
and experimental knowledge to the application of science in the
mechanic arts, we may, however, go too far. The incentives to
substitute general for special knowledge are so many, that it may
lead us to forget or underrate that part which cannot come within
general rules.
The labour, dirt, and self-denial inseparable from the acquirement
of special knowledge in the mechanic arts are strong reasons
for augmenting the importance and completeness of theoretical
knowledge, and while it should be, as it is, the constant object to
bring everything, even manipulative processes, so far as possible,
within general rules, it must not be forgotten that there is a
limit in this direction.
In England and America the evils which arise from a false or over
estimate of mere theoretical knowledge have thus far been avoided.
Our workshops are yet, and must long remain, our technological
schools. The money value of bare theoretical training is so fast
declining that we may be said to have passed the point of reaction,
and that the importance of sound practical knowledge is beginning
to be more felt than it was some years ago. It is only in those
countries where actual manufactures and other practical tests are
wanting, that any serious mistake can be made as to what should
constitute an education in mechanics. Our workshops, if other means
fail, will fix such a standard; and it is encouraging to find
here and there among the outcry for technical training, a note of
warning as to the means to be employed.
During the meeting of the British Association in Belfast (1874),
the committee appointed to investigate the means of teaching
Physical Science, reported that "the most serious obstacle
discovered was an absence from the minds of the pupils of a firm
and clear grasp of the concrete facts forming a base of the
reasoning processes they are called upon to study; and that the
use of text-books should be made subordinate to an attendance upon
lectures and demonstrations."
Here, in reference to teaching science, and by an authority which
should command our highest confidence, we have a clear exposition
of the conditions which surround mechanical training, with,
however, this difference, that in the latter "demonstration" has
its greatest importance.
Professor John Sweet of Cornell University, in America, while
delivering an address to the mechanical engineering classes,
during the same year, made use of the following words: "It is not
what you 'know' that you will be paid for; it is what you can
'perform,' that must measure the value of what you learn here."
These few words contain a truth which deserves to be earnestly
considered by every student engineer or apprentice; as a maxim
it will come forth and apply to nearly everything in subsequent
practice.
I now come to speak directly of the present work and its objects.
It may be claimed that a book can go no further in treating of
mechanical manipulation than principles or rules will reach, and
that books must of necessity be confined to what may be called
generalities. This is in a sense true, and it is, indeed, a most
difficult matter to treat of machine operations and shop processes;
but the reason is that machine operations and shop processes have
not been reduced to principles or treated in the same way as
strains, proportions, the properties of material, and so on. I do
not claim that manipulative processes can be so generalised--this
would be impossible; yet much can be done, and many things regarded
as matters of special knowledge can be presented in a way to
come within principles, and thus rendered capable of logical
investigation.
Writers on mechanical subjects, as a rule, have only theoretical
knowledge, and consequently seldom deal with workshop processes.
Practical engineers who have passed through a successful experience
and gained that knowledge which is most difficult for apprentices
to acquire, have generally neither inclination nor incentives to
write books. The changes in manipulation are so frequent, and the
operations so diversified, that practical men have a dread of the
criticisms which such changes and the differences of opinion may
bring forth; to this may be added, that to become a practical
mechanical engineer consumes too great a share of one's life to
leave time for other qualifications required in preparing books.
For these reasons "manipulation" has been neglected, and for the
same reasons must be imperfectly treated here. The purpose is not
so much to instruct in shop processes as to point out how they can
be best learned, the reader for the most part exercising his own
judgment and reasoning powers. It will be attempted to point out
how each simple operation is governed by some general principle,
and how from such operations, by tracing out the principle which
lies at the bottom, it is possible to deduce logical conclusions
as to what is right or wrong, expedient or inexpedient. In this
way, it is thought, can be established a closer connection between
theory and practice, and a learner be brought to realise that he
has only his reasoning powers to rely on; that formulæ, rules,
tables, and even books, are only aids to this reasoning power,
which alone can master and combine the symbol and the substance.
No computations, drawings, or demonstrations of any kind will
be employed to relieve the mind of the reader from the care of
remembering and a dependence on his own exertions. Drawings,
constants, formulæ, tables, rules, with all that pertains to
computation in mechanics, are already furnished in many excellent
books, which leave nothing to be added, and such books can be
studied at the same time with what is presented here.
The book has been prepared with a full knowledge of the fact, that
what an apprentice may learn, as well as the time that is consumed
in learning, are both measured by the personal interest felt in
the subject studied, and that such a personal interest on the part
of an apprentice is essential to permanent success as an engineer.
A general dryness and want of interest must in this, as in all
cases, be a characteristic of any writing devoted to mechanical
subjects: some of the sections will be open to this charge, no
doubt, especially in the first part of the book; but it is trusted
that the good sense of the reader will prevent him from passing
hurriedly over the first part, to see what is said, at the end, of
casting, forging, and fitting, and will cause him to read it as it
comes, which will in the end be best for the reader, and certainly
but fair to the writer.
CHAPTER I.
_PLANS OF STUDYING._
By examining the subject of applied mechanics and shop
manipulation, a learner may see that the knowledge to be acquired
by apprentices can be divided into two departments, that may be
called general and special. General knowledge relating to tools,
processes and operations, so far as their construction and action
may be understood from general principles, and without special
or experimental instruction. Special knowledge is that which is
based upon experiment, and can only be acquired by special, as
distinguished from general sources.
To make this plainer, the laws of forces, the proportion of parts,
strength of material, and so on, are subjects of general knowledge
that may be acquired from books, and understood without the aid
of an acquaintance with the technical conditions of either the
mode of constructing or the manner of operating machines; but
how to construct proper patterns for castings, or how the parts
of machinery should be moulded, forged, or fitted, is special
knowledge, and must have reference to particular cases. The
proportions of pulleys, bearings, screws, or other regular details
of machinery, may be learned from general rules and principles,
but the hand skill that enters into the manufacture of these
articles cannot be learned except by observation and experience.
The general design, or the disposition of metal in machine-framing,
can be to a great extent founded upon rules and constants that have
general application; but, as in the case of wheels, the plans of
moulding such machine frames are not governed by constant rules or
performed in a uniform manner. Patterns of different kinds may be
employed; moulds may be made in various ways, and at a greater and
less expense; the metal can be mixed to produce a hard or a soft
casting, a strong or a weak one; the conditions under which the
metal is poured may govern the soundness or shrinkage,--things that
are determined by special instead of general conditions.
The importance of a beginner learning to divide what he has to
learn into these two departments of special and general, has the
advantage of giving system to his plans, and pointing out that
part of his education which must be acquired in the workshop and
by practical experience. The time and opportunities which might
be devoted to learning the technical manipulations of a foundry,
for instance, would be improperly spent if devoted to metallurgic
chemistry, because the latter may be studied apart from practical
foundry manipulation, and without the opportunity of observing
casting operations.
It may also be remarked that the special knowledge involved in
applied mechanics is mainly to be gathered and retained by personal
observation and memory, and that this part is the greater one;
all the formulæ relating to machine construction may be learned
in a shorter time than is required to master and understand the
operations which may be performed on an engine lathe. Hence first
lessons, learned when the mind is interested and active, should
as far as possible include whatever is special; in short, no
opportunity of learning special manipulation should be lost. If a
wheel pattern come under notice, examine the manure in which it is
framed together, the amount of draught, and how it is moulded, as
well as to determine whether the teeth have true cycloidal curves.
Once, nearly all mechanical knowledge was of the class termed
special, and shop manipulations were governed by empirical rules
and the arbitrary opinions of the skilled; an apprentice entered a
shop to learn a number of mysterious operations, which could not be
defined upon principles, and only understood by special practice
and experiment. The arrangement and proportions of mechanism were
also determined by the opinions of the skilled, and like the
manipulation of the shop, were often hid from the apprentice, and
what he carried in his memory at the end of an apprenticeship was
all that he had gained. The tendency of this was to elevate those
who were the fortunate possessors of a strong natural capacity,
and to depress the position of those less fortunate in the matter
of mechanical "genius," as it was called. The ability to prepare
proper designs, and to succeed in original plans, was attributed
to a kind of intuitive faculty of the mind; in short, the mechanic
arts were fifty years ago surrounded by a superstition of a
different nature, but in its influences the same as superstition in
other branches of knowledge.
But now all is changed: natural phenomena have been explained
as being but the operation of regular laws; so has mechanical
manipulation been explained as consisting in the application of
general principles, not yet fully understood, but far enough,
so that the apprentice may with a substantial education, good
reasoning powers, and determined effort, force his way where once
it had to be begged. The amount of special knowledge in mechanical
manipulation, that which is irregular and modified by special
conditions, is continually growing less as generalisation and
improvement go on.
Another matter to be considered is that the engineering apprentice,
in estimating what he will have to learn, must not lose sight of
the fact that what qualifies an engineer of to-day will fall far
short of the standard that another generation will fix, and of that
period in which his practice will fall. This I mention because it
will have much to do with the conceptions that a learner will form
of what he sees around him. To anticipate improvement and change is
not only the highest power to which a mechanical engineer can hope
to attain, but is the key to his success.
By examining the history of great achievements in the mechanic
arts, it will be seen that success has been mainly dependent upon
predicting future wants, as well as upon an ability to supply such
wants, and that the commercial value of mechanical improvements
is often measured by conditions that the improvements themselves
anticipate. The invention of machine-made drills, for example,
was but a small matter; but the demand that has grown up since,
and because of their existence, has rendered this improvement one
of great value. Moulded bearings for shafts were also a trifling
improvement when first made, but it has since influenced machine
construction in America in a way that has given great importance to
the invention.
It is generally useless and injudicious to either expect or to
search after radical changes or sweeping improvements in machine
manufacture or machine application, but it is important in learning
how to construct and apply machinery, that the means of foreseeing
what is to come in future should at the same time be considered.
The attention of a learner can, for example, be directed to the
division of labour, improvements in shop system, how and where
commercial interests are influenced by machinery, what countries
are likely to develop manufactures, the influence of steam-hammers
on forging, the more extended use of steel when cheapened by
improved processes for producing it, the division of mechanical
industry into special branches, what kind of machinery may become
staple, such as shafts, pulleys, wheels, and so on. These things
are mentioned at random, to indicate what is meant by looking into
the future as well as at the present.
Following this subject of future improvement farther, it may be
assumed that an engineer who understands the application and
operation of some special machine, the principles that govern its
movements, the endurance of the wearing surfaces, the direction and
measure of the strains, and who also understands the principles of
the distribution of material, arrangement, and proportions,--that
such an engineer will be able to construct machines, the plans of
which will not be materially departed from so long as the nature
of the operations to which the machines are applied remain the same.
A proof of this proposition is furnished in the case of standard
machine tools for metal-cutting, a class of machinery that for many
years past has received the most thorough attention at the hands of
our best mechanical engineers.
Standard tools for turning, drilling, planing, boring, and so
on, have been changed but little during twenty years past, and
are likely to remain quite the same in future. A lathe or a
planing-machine made by a first-class establishment twenty years
ago has, in many cases, the same capacity, and is worth nearly
as much in value at the present time as machine tools of modern
construction--a test that more than any other determines their
comparative efficiency and the true value of the improvements
that have been made. The plans of the framing for machine tools
have been altered, and many improvements in details have been
added; yet, upon the whole, it is safe to assume, as before said,
that standard tools for metal-cutting have reached a state of
improvement that precludes any radical changes in future, so long
as the operations in metal-cutting remain the same.
This state of improvement which has been reached in machine-tool
manufacture, is not only the result of the skill expended on such
tools, but because as a notable exception they are the agents of
their own production; that is, machine tools produce machine tools,
and a maker should certainly become skilled in the construction of
implements which he employs continually in his own business. This
peculiarity of machine-tool manufactures is often overlooked by
engineers, and unfair comparisons made between machines of this
class and those directed to wood conversion and other manufacturing
processes, which machinists, as a rule, do not understand.
Noting the causes and conditions which have led to this perfection
in machine-tool manufacture, and how far they apply in the case of
other classes of machinery, will in a measure indicate the probable
improvements and changes that the future will produce.
The functions and adaptations of machinery constitute, as already
explained, the science of mechanical engineering. The functions
of a machine are a foundation on which its plans are based; hence
machine functions and machine effect are matters to which the
attention of an apprentice should first be directed.
In the class of mechanical knowledge that has been defined as
general, construction comes in the third place: first, machine
functions; next, plans or adaptation of machines; and third, the
manner of constructing machines. This should be the order of study
pursued in learning mechanical manipulation. Instead of studying
how drilling-machines, planing-machines or lathes are arranged,
and next plans of constructing them, and then the principles of
their operation, which is the usual course, the learner should
reverse the order, studying, first, drilling, planing, and turning
as operations; next, the adaptation of tools for the purposes; and
third, plans of constructing such tools.
Applied to steam-engines, the same rule holds good. Steam, as a
motive agent, should first be studied, then the operation of steam
machinery, and finally the construction of steam-engines. This is a
rule that may not apply in all cases, but the exceptions are few.
To follow the same chain of reasoning still farther, and to show
what may be gained by method and system in learning mechanics, it
may be assumed that machine functions consist in the application of
power, and therefore power should be first studied; of this there
can be but one opinion. The learner who sets out to master even the
elementary principles of mechanics without first having formed a
true conception of power as an element, is in a measure wasting his
time and squandering his efforts.
Any truth in mechanics, even the action of the "mechanical powers"
before alluded to, is received with an air of mystery, unless the
nature of power is first understood. Practical demonstration a
hundred times repeated does not create a conviction of truth in
mechanical propositions, unless the principles of operation are
understood.
An apprentice may learn that power is not increased or diminished
by being transmitted through a train of wheels which change both
speed and force, and he may believe the proposition without having
a "conviction" of its truth. He must first learn to regard power
as a constant and indestructible element--something that may be
weighed, measured, and transmitted, but not created or destroyed by
mechanism; then the nature of the mechanism may be understood, but
not before.
To obtain a true understanding of the nature of power is by no
means the difficulty for a beginner that is generally supposed;
and when once reached, the truth will break upon the mind like a
sudden discovery, and ever afterwards be associated with mechanism
and motion whenever seen. The learner will afterwards find himself
analysing the flow of water, the traffic in the streets, the
movement of ships and trains; even the act of walking will become
a manifestation of power, all clear and intelligible, without that
air of mystery that is otherwise inseparable from the phenomena of
motion. If the learner will go on farther, and study the connection
between heat and force, the mechanical equivalent of heat when
developed into force and motion, and the reconversion of power into
heat, he will have commenced at the base of what must constitute
a thorough knowledge of mechanics, without which he will have to
continually proceed under difficulties.
I am well aware of the popular opinion that such subjects
are too abstruse to be understood by practical mechanics--an
assumption that is founded mainly in the fact that the subject
of heat and motion are not generally studied, and have been too
recently demonstrated in a scientific way to command confidence
and attention; but the subject is really no more difficult to
understand in an elementary sense than that of the relation between
movement and force illustrated in the "mechanical powers" of
school-books, which no apprentice ever did or ever will understand,
except by first studying the principles of force and motion,
independent of mechanical agents, such as screws, levers, wedges,
and so on.
It is to be regretted that there have not been books especially
prepared to instruct mechanical students in the relations between
heat, force, motion, and practical mechanism. The subject is,
of course, treated at great length in modern scientific works,
but is not connected with the operations of machinery in a way
to be easily understood by beginners. A treatise on the subject,
called "The Correlation and Conservation of Forces," published
by D. Appleton & Co. of New York, is perhaps as good a book on
the subject as can at this time be referred to. The work contains
papers contributed by Professors Carpenter, Grove, Helmholtz,
Faraday, and others, and has the advantage of arrangement in short
sections, that compass the subject without making it tedious.
In respect to books and reading, the apprentice should supply
himself with references. A single book, and the best one that can
be obtained on each of the different branches of engineering,
is enough to begin with. A pocket-book for reference, such as
Molesworth's or Nystrom's, is of use, and should always be at
hand. For general reading, nothing compares with the scientific
and technical journals, which are now so replete with all kinds
of information. Beside noting the present progress of engineering
industry in all parts of the world, they contain nearly all besides
that a learner will require.
It will be found that information of improvements and mechanical
progress that a learner may gather from serial publications can
always be exchanged for special knowledge in his intercourse with
skilled workmen, who have not the opportunity or means of reading
for themselves; and what an apprentice may read and learn in an
hour can often be "exchanged" for experimental knowledge that has
cost years to acquire.
(1.) Into what two divisions can a knowledge of constructive
mechanics be divided?--(2.) Give an example of your own to
distinguish between special and general knowledge.--(3.) In
what manner is special knowledge mostly acquired?--(4.) What
has been the effect of scientific investigations upon special
knowledge?--(5.) What is meant by the division of labour?--(6.)
Why have engineering tools been less changed than most other
kinds of machinery during twenty years past?--(7.) What is meant
by machine functions; adaptation; construction?--(8.) Why has the
name "mechanical powers" been applied to screws, levers, wedges,
and so on?--(9.) Can power be conceived of as an element or
principle, independent of mechanism?