On the Economy of Machinery and Manufactures
by
Charles Babbage
Part 1 out of 6
This etext was produced by Charles Aldarondo Aldarondo@yahoo.com
On the Economy of Machinery and Manufactures
by Charles Babbage
1832
Preface
The present volume may be considered as one of the
consequences that have resulted from the calculating engine, the
construction of which I have been so long superintending. Having
been induced, during the last ten years, to visit a considerable
number of workshops and factories, both in England and on the
Continent, for the purpose of endeavouring to make myself
acquainted with the various resources of mechanical art, I was
insensibly led to apply to them those principles of
generalization to which my other pursuits had naturally given
rise. The increased number of curious processes and interesting
facts which thus came under my attention, as well as of the
reflections which they suggested, induced me to believe that the
publication of some of them might be of use to persons who
propose to bestow their attention on those enquiries which I have
only incidentally considered. With this view it was my intention
to have delivered the present work in the form of a course of
lectures at Cambridge; an intention which I was subsequently
induced to alter. The substance of a considerable portion of it
has, however, appeared among the preliminary chapters of the
mechanical part of the Encyclopedia Metropolitana.
I have not attempted to offer a complete enumeration of all
the mechanical principles which regulate the application of
machinery to arts and manufactures, but I have endeavoured to
present to the reader those which struck me as the most
important, either for understanding the actions of machines, or
for enabling the memory to classify and arrange the facts
connected with their employment. Still less have I attempted to
examine all the difficult questions of political economy which
are intimately connected with such enquiries. It was impossible
not to trace or to imagine, among the wide variety of facts
presented to me, some principles which seemed to pervade many
establishments; and having formed such conjectures, the desire to
refute or to verify them, gave an additional interest to the
pursuit. Several of the principles which I have proposed, appear
to me to have been unnoticed before. This was particularly the
case with respect to the explanation I have given of the division
of labour; but further enquiry satisfied me that I had been
anticipated by M. Gioja, and it is probable that additional
research would enable me to trace most of the other principles,
which I had thought original, to previous writers, to whose merit
I may perhaps be unjust, from my want of acquaintance with the
historical branch of the subject.
The truth however of the principles I have stated, is of much
more importance than their origin; and the utility of an enquiry
into them, and of establishing others more correct, if these
should be erroneous, can scarcely admit of a doubt.
The difficulty of understanding the processes of manufactures
has unfortunately been greatly overrated. To examine them with
the eye of a manufacturer, so as to be able to direct others to
repeat them, does undoubtedly require much skill and previous
acquaintance with the subject; but merely to apprehend their
general principles and mutual relations, is within the power of
almost every person possessing a tolerable education.
Those who possess rank in a manufacturing country, can
scarcely be excused if they are entirely ignorant of principles,
whose development has produced its greatness. The possessors of
wealth can scarcely be indifferent to processes which, nearly or
remotely have been the fertile source of their possessions. Those
who enjoy leisure can scarcely find a more interesting and
instructive pursuit than the examination of the workshops of
their own country, which contain within them a rich mine of
knowledge, too generally neglected by the wealthier classes.
It has been my endeavour, as much as possible, to avoid all
technical terms, and to describe, in concise language, the arts I
have had occasion to discuss. In touching on the more abstract
principles of political economy, after shortly stating the
reasons on which they are founded, I have endeavoured to support
them by facts and anecdotes; so that whilst young persons might
be amused and instructed by the illustrations, those of more
advanced judgement may find subject for meditation in the general
conclusions to which they point. I was anxious to support the
principles which I have advocated by the observations of others,
and in this respect I found myself peculiarly fortunate. The
reports of committees of the House of Commons, upon various
branches of commerce and manufactures, and the evidence which
they have at different periods published on those subjects, teem
with information of the most important kind, rendered doubly
valuable by the circumstances under which it has been collected.
From these sources I have freely taken, and I have derived some
additional confidence from the support they have afforded to my
views. *
Charles Babbage
Dorset Street
Manchester Square
8 June, 1832
[*Footnote: I am happy to avail myself of this occasion of expressing
my obligations to the Right Hon. Manners Sutton, the Speaker of the
House of Commons, to whom I am indebted for copies of a considerable
collection of those reports.]
Preface to the Second Edition
In two months from the publication of the first edition of
this volume, three thousand copies were in the hands of the
public. Very little was spent in advertisements; the booksellers,
instead of aiding, impeded its sale; * it formed no part of any
popular series and yet the public, in a few weeks, purchased the
whole edition. Some small part of this success, perhaps, was due
to the popular exposition of those curious processes which are
carried on in our workshops, and to the endeavour to take a short
view of the general principles which direct the manufactories of
the country. But the chief reason was the commanding attraction
of the subject, and the increasing desire to become acquainted
with the pursuits and interests of that portion of the people
which has recently acquired so large an accession of political
influence.
[*Footnote: I had good evidence of this fact from various quarters;
and being desirous of verifying it, I myself applied for a copy at
the shop of a bookseller of respectability, who is probably not aware
that he refused to procure one even for its author.]
A greater degree of attention than I had expected has been
excited by what I have stated in the first edition, respecting
the 'Book-trade'. Until I had commenced the chapter, 'On the
separate cost of each process of a manufacture', I had no
intention of alluding to that subject: but the reader will
perceive that I have throughout this volume, wherever I could,
employed as illustrations, objects of easy access to the reader;
and, in accordance with that principle, I selected the volume
itself. When I arrived at the chapter, 'On combinations of
masters against the public', I was induced, for the same reason,
to expose a combination connected with literature, which, in my
opinion, is both morally and politically wrong. I entered upon
this enquiry without the slightest feeling of hostility to that
trade, nor have I any wish unfavourable to it; but I think a
complete reform in its system would add to its usefulness and
respectability. As the subject of that chapter has been much
discussed, I have thought it right to take a view of the various
arguments which have been advanced, and to offer my own opinion
respecting their validity--and there I should have left the
subject, content to allow my general character to plead for me
against insinuations respecting my motives--but as the remarks
of some of my critics affect the character of another person, I
think it but just to state circumstances which will clearly
disprove them.
Mr Fellowes, of Ludgate Street, who had previously been the
publisher of some other volumes for me, had undertaken the
publication of the first edition of the present work. A short
time previous to its completion, I thought it right to call his
attention to the chapter in which the book-trade is discussed;
with the view both of making him acquainted with what I had
stated, and also of availing myself of his knowledge in
correcting any accidental error as to the facts. Mr Fellowes,
'differing from me entirely respecting the conclusions I had
arrived at', then declined the publication of the volume. If I
had then chosen to apply to some of those other booksellers,
whose names appear in the Committee of 'The Trade', it is
probable that they also would have declined the office of
publishing for me; and, had my object been to make a case against
the trade, such a course would have assisted me. But I had no
such feeling; and having procured a complete copy of the whole
work, I called with it on Mr Knight, of Pall Mall East, whom
until that day I had never seen, and with whom I had never
previously had the slightest communication. I left the book in Mr
Knight's hands, with a request that, when he had read it, I might
be informed whether he would undertake the publication of it; and
this he consented to do. Mr Knight, therefore, is so far from
being responsible for a single opinion in the present volume,
that he saw it only, for a short time, a few days previous to its
publication.
It has been objected to me, that I have exposed too freely
the secrets of trade. The only real secrets of trade are
industry, integrity, and knowledge: to the possessors of these no
exposure can be injurious; and they never fail to produce respect
and wealth.
The alterations in the present edition are so frequent, that
I found it impossible to comprise them in a supplement. But the
three new chapters, 'On money as a medium of exchange'; 'On a new
system of manufacturing'; and 'On the effect of machinery in
reducing the demand for labour'; will shortly be printed
separately, for the use of the purchasers of the first edition.
I am inclined to attach some importance to the new system of
manufacturing; and venture to throw it out with the hope of its
receiving a full discussion among those who are most interested
in the subject. I believe that some such system of conducting
manufactories would greatly increase the productive powers of any
country adopting it; and that our own possesses much greater
facilities for its application than other countries, in the
greater intelligence and superior education of the working
classes. The system would naturally commence in some large town,
by the union of some of the most prudent and active workmen; and
their example, if successful, would be followed by others. The
small capitalist would next join them, and such factories would
go on increasing until competition compelled the large capitalist
to adopt the same system; and, ultimately, the whole faculties of
every man engaged in manufacture would be concentrated upon one
object--the art of producing a good article at the lowest
possible cost--whilst the moral effect on that class of the
population would be useful in the highest degree, since it would
render character of far greater value to the workman than it is
at present.
To one criticism which has been made, this volume is
perfectly open. I have dismissed the important subject of the
patent-laws in a few lines. The subject presents, in my opinion,
great difficulties, and I have been unwilling to write upon it,
because I do not see my way. I will only here advert to one
difficulty. What constitutes an invention? Few simple mechanical
contrivances are new; and most combinations may be viewed as
species, and classed under genera of more or less generality; and
may, in consequence, be pronounced old or new, according to the
mechanical knowledge of the person who gives his opinion.
Some of my critics have amused their readers with the
wildness of the schemes I have occasionally thrown out; and I
myself have sometimes smiled along with them. Perhaps it were
wiser for present reputation to offer nothing but profoundly
meditated plans, but I do not think knowledge will be most
advanced by that course; such sparks may kindle the energies of
other minds more favourably circumstanced for pursuing the
enquiries. Thus I have now ventured to give some speculations on
the mode of blowing furnaces for smelting iron; and even
supposing them to be visionary, it is of some importance thus to
call the attention of a large population, engaged in one of our
most extensive manufactures, to the singular fact, that
four-fifths of the steam power used to blow their furnaces
actually cools them.
I have collected, with some pains, the criticisms* on the
first edition of this work, and have availed myself of much
information which has been communicated to me by my friends, for
the improvement of the present volume. If I have succeeded in
expressing that I had to explain with perspicuity, I am aware
that much of this clearness is due to my friend, Dr Fitton, to
whom both the present and the former edition are indebted for
such an examination and correction, as an author himself has very
rarely the power to bestow.
[*Footnote: Several of these have probably escaped me, and I shall
feel indebted to any one who will inform my publisher of any future
remarks.]
22 November, 1832.
Section I.
INTRODUCTION.
The object of the present volume is to point out the effects
and the advantages which arise from the use of tools and
machines;--to endeavour to classify their modes of action;--and to
trace both the causes and the consequences of applying machinery
to supersede the skill and power of the human arm.
A view of the mechanical part of the subject will, in the
first instance, occupy our attention, and to this the first
section of the work will be devoted. The first chapter of the
section will contain some remarks on the general sources from
whence the advantages of machinery are derived, and the
succeeding nine chapters will contain a detailed examination of
principles of a less general character. The eleventh chapter
contains numerous subdivisions, and is important from the
extensive classification it affords of the arts in which copying
is so largely employed. The twelfth chapter, which completes the
first section, contains a few suggestions for the assistance of
those who propose visiting manufactories.
The second section, after an introductory chapter on the
difference between making and manufacturing, will contain, in the
succeeding chapters, a discussion of many of the questions which
relate to the political economy of the subject. It was found that
the domestic arrangement, or interior economy of factories, was
so interwoven with the more general questions, that it was deemed
unadvisable to separate the two subjects. The concluding chapter
of this section, and of the work itself, relates to the future
prospects of manufactures, as arising from the application of
science.
Chapter 1
Sources of the Advantages arising from Machinery and Manufactures
1. There exists, perhaps, no single circumstance which
distinguishes our country more remarkably from all others, than
the vast extent and perfection to which we have carried the
contrivance of tools and machines for forming those conveniences
of which so large a quantity is consumed by almost every class of
the community. The amount of patient thought, of repeated
experiment, of happy exertion of genius, by which our
manufactures have been created and carried to their present
excellence, is scarcely to be imagined. If we look around the
rooms we inhabit, or through those storehouses of every
convenience, of every luxury that man can desire, which deck the
crowded streets of our larger cities, we shall find in the
history of each article, of every fabric, a series of failures
which have gradually led the way to excellence; and we shall
notice, in the art of making even the most insignificant of them,
processes calculated to excite our admiration by their
simplicity, or to rivet our attention by their unlooked-for
results.
2. The accumulation of skill and science which has been
directed to diminish the difficulty of producing manufactured
goods, has not been beneficial to that country alone in which it
is concentrated; distant kingdoms have participated in its
advantages. The luxurious natives of the East,(1*) and the ruder
inhabitants of the African desert are alike indebted to our
looms. The produce of our factories has preceded even our most
enterprising travellers.(2*) The cotton of India is conveyed by
British ships round half our planet, to be woven by British skill
in the factories of Lancashire: it is again set in motion by
British capital; and, transported to the very plains whereon it
grew, is repurchased by the lords of the soil which gave it
birth, at a cheaper price than that at which their coarser
machinery enables them to manufacture it themselves.(3*)
3. The large proportion of the population of this country,
who are engaged in manufactures, appears from the following table
deduced from a statement in an Essay on the Distribution of
Wealth, by the Rev. R. Jones:
For every hundred persons employed in agriculture, there are:
Agriculturists Non-agriculturists
In Bengal 100 25
In Italy 100 31
In France 100 50
In England 100 200
The fact that the proportion of non-agricultural to
agricultural persons is continually increasing, appears both from
the Report of the Committee of the House of Commons upon
Manufacturers' Employment, July, 1830, and from the still later
evidence of the last census; from which document the annexed
table of the increase of population in our great manufacturing
towns, has been deduced.
Increase of population per cent
Names of places
1801-11 1811-21 1821-31 Total
Manchester 22 40 47 151
Glasgow 30 46 38 161
Liverpool(4*) 26 31 44 138
Nottingham 19 18 25 75
Birmingham 16 24 33 90
Great Britain 14.2 15.7 15.5 52.5
Thus, in three periods of ten years, during each of which the
general population of the country has increased about 15 per
cent, or about 52 per cent upon the whole period of thirty years,
the population of these towns has, on the average, increased 132
per cent. After this statement, there requires no further
argument to demonstrate the vast importance to the well-being of
this country, of making the interests of its manufacturers well
understood and attended to.
4. The advantages which are derived from machinery and
manufactures seem to arise principally from three sources: The
addition which they make to human power. The economy they produce
of human time. The conversion of substances apparently common and
worthless into valuable products.
5. Of additions to human power. With respect to the first of
these causes, the forces derived from wind, from water, and from
steam, present themselves to the mind of every one; these are, in
fact, additions to human power, and will be considered in a
future page: there are, however, other sources of its increase,
by which the animal force of the individual is itself made to act
with far greater than its unassisted power; and to these we shall
at present confine our observations.
The construction of palaces, of temples, and of tombs, seems
to have occupied the earliest attention of nations just entering
on the career of civilization; and the enormous blocks of stone
moved from their native repositories to minister to the grandeur
or piety of the builders, have remained to excite the
astonishment of their posterity, long after the purposes of many
of these records, as well as the names of their founders, have
been forgotten. The different degrees of force necessary to move
these ponderous masses, will have varied according to the
mechanical knowledge of the people employed in their transport;
and that the extent of power required for this purpose is widely
different under different circumstances, will appear from the
following experiment, which is related by M. Rondelet, Sur L'Art
de Batir. A block of squared stone was taken for the subject of
experiment:
1. Weight of stone 1080 lbs
2. In order to drag this stone along the floor of the quarry,
roughly chiselled, it required a force equal to 758 lbs
3. The same stone dragged over a floor of planks required 652 lbs
4. The same stone placed on a platform of wood, and dragged over
a floor of planks, required 606 lbs
5. After soaping the two surfaces of wood which slid over each
other, it required 182 lbs
6. The same stone was now placed upon rollers of three inches
diameter, when it required to put it in motion along the floor of
the quarry 34 lbs
7. To drag it by these rollers over a wooden floor 28 lbs
8. When the stone was mounted on a wooden platform, and the same
rollers placed between that and a plank floor, it required 22 lbs
From this experiment it results, that the force necessary to
move a stone along
Part of its weight
The roughly chiselled floor of its quarry is nearly 2/3
Along a wooden floor 3/5
By wood upon wood 5/9
If the wooden surfaces are soaped 1/6
With rollers on the floor of the quarry 1/32
On rollers on wood 1/40
On rollers between wood 1/50
At each increase of knowledge, as well as on the contrivance
of every new tool, human labour becomes abridged. The man who
contrived rollers, invented a tool by which his power was
quintupled. The workman who first suggested the employment of
soap or grease, was immediately enabled to move, without exerting
a greater effort, more than three times the weight he could
before.(5*)
6. The economy of human time is the next advantage of
machinery in manufactures. So extensive and important is this
effect, that we might, if we were inclined to generalize, embrace
almost all the advantages under this single head: but the
elucidation of principles of less extent will contribute more
readily to a knowledge of the subject; and, as numerous examples
will be presented to the reader in the ensuing pages, we shall
restrict our illustrations upon this point.
As an example of the economy of time, the use of gunpowder in
blasting rocks may be noticed. Several pounds of powder may be
purchased for a sum acquired by a few days' labour: yet when this
is employed for the purpose alluded to, effects are frequently
produced which could not, even with the best tools, be
accomplished by other means in less than many months.
The dimensions of one of the blocks of limestone extracted
from the quarries worked for the formation of the breakwater at
Plymouth were 26 1/2 ft long, 13 ft wide, and 16 ft deep. This
mass, containing above 4,800 cubic feet, and weighing about 400
tons, was blasted three times. Two charges of 50 lbs each were
successively exploded in a hole 13 feet deep, the bore being 3
inches at top and 2 1/2 inches at bottom: 100 lbs of powder were
afterwards exploded in the rent formed by those operations. Each
pound of gunpowder separated from the rock two tons of matter, or
nearly 4,500 times its own weight. The expense of the powder was
L 6, or nearly 7 1/2d. per lb: the boring occupied two men during
a day and a half, and cost about 9s.; and the value of the
produce was, at that time, about L 45.
7. The simple contrivance of tin tubes for speaking through,
communicating between different apartments, by which the
directions of the superintendent are instantly conveyed to the
remotest parts of an establishment, produces a considerable
economy of time. It is employed in the shops and manufactories in
London, and might with advantage be used in domestic
establishments, particularly in large houses, in conveying orders
from the nursery to the kitchen, or from the house to the stable.
Its convenience arises not merely from saving the servant or
workman useless journeys to receive directions, but from
relieving the master himself from that indisposition to give
trouble, which frequently induces him to forego a trifling want,
when he knows that his attendant must mount several flights of
stairs to ascertain his wishes, and, after descending, must mount
again to supply them. The distance to which such a mode of
communication can be extended, does not appear to have been
ascertained, and would be an interesting subject for enquiry.
Admitting it to be possible between London and Liverpool, about
seventeen minutes would elapse before the words spoken at one end
would reach the other extremity of the pipe.
8. The art of using the diamond for cutting glass has
undergone, within a few years, a very important improvement. A
glazier's apprentice, when using a diamond set in a conical
ferrule, as was always the practice about twenty years since,
found great difficulty in acquiring the art of using it with
certainty; and, at the end of a seven years' apprenticeship, many
were found but indifferently skilled in its employment. This
arose from the difficulty of finding the precise angle at which
the diamond cuts, and of guiding it along the glass at the proper
inclination when that angle is found. Almost the whole of the
time consumed and of the glass destroyed in acquiring the art of
cutting glass, may now be saved by the use of an improved tool.
The gem is set in a small piece of squared brass with its edges
nearly parallel to one side of the square. A person skilled in
its use now files away the brass on one side until, by trial, he
finds that the diamond will make a clean cut, when guided by
keeping this edge pressed against a ruler. The diamond and its
mounting are now attached to a stick like a pencil, by means of a
swivel allowing a small angular motion. Thus, even the beginner
at once applies the cutting edge at the proper angle, by pressing
the side of the brass against a ruler; and even though the part
he holds in his hand should deviate a little from the required
angle, it communicates no irregularity to the position of the
diamond, which rarely fails to do its office when thus employed.
The relative hardness of the diamond, in different
directions, is a singular fact. An experienced workman, on whose
judgement I can rely, informed me that he has seen a diamond
ground with diamond powder on a cast-iron mill for three hours
without its being at all worn, but that, on changing its
direction with respect to the grinding surface, the same edge was
ground away.
9. Employment of materials of little value. The skins used by
the goldbeater are produced from the offal of animals. The hoofs
of horses and cattle, and other horny refuse, are employed in the
production of the prussiate of potash, that beautiful, yellow,
crystallized salt, which is exhibited in the shops of some of our
chemists. The worn-out saucepans and tinware of our kitchens,
when beyond the reach of the tinker's art, are not utterly
worthless. We sometimes meet carts loaded with old tin kettles
and worn-out iron coal-skuttles traversing our streets. These
have not yet completed their useful course; the less corroded
parts are cut into strips, punched with small holes, and
varnished with a coarse black varnish for the use of the
trunk-maker, who protects the edges and angles of his boxes with
them; the remainder are conveyed to the manufacturing chemists in
the outskirts of the town, who employ them in combination with
pyroligneous acid, in making a black die for the use of calico
printers.
10. Of tools. The difference between a tool and a machine is
not capable of very precise distinction; nor is it necessary, in
a popular explanation of those terms, to limit very strictly
their acceptation. A tool is usually more simple than a machine;
it is generally used with the hand, whilst a machine is
frequently moved by animal or steam power. The simpler machines
are often merely one or more tools placed in a frame, and acted
on by a moving power. In pointing out the advantages of tools, we
shall commence with some of the simplest.
11. To arrange twenty thousand needles thrown promiscuously
into a box, mixed and entangled in every possible direction, in
such a form that they shall be all parallel to each other, would,
at first sight, appear a most tedious occupation; in fact, if
each needle were to be separated individually, many hours must be
consumed in the process. Yet this is an operation which must be
performed many times in the manufacture of needles; and it is
accomplished in a few minutes by a very simple tool; nothing more
being requisite than a small flat tray of sheet iron, slightly
concave at the bottom. In this the needles are placed, and shaken
in a peculiar manner, by throwing them up a very little, and
giving at the same time a slight longitudinal motion to the tray.
The shape of the needles assists their arrangement; for if two
needles cross each other (unless, which is exceedingly
improbable, they happen to be precisely balanced), they will,
when they fall on the bottom of the tray, tend to place
themselves side by side, and the hollow form of the tray assists
this disposition. As they have no projection in any part to
impede this tendency, or to entangle each other, they are, by
continually shaking, arranged lengthwise, in three or four
minutes. The direction of the shake is now changed, the needles
are but little thrown up, but the tray is shaken endways; the
result of which is, that in a minute or two the needles which
were previously arranged endways become heaped up in a wall, with
their ends against the extremity of the tray. They are then
removed, by hundreds at a time, with a broad iron spatula, on
which they are retained by the forefinger of the left hand. As
this parallel arrangement of the needles must be repeated many
times, if a cheap and expeditious method had not been devised,
the expense of the manufacture would have been considerably
enhanced.
12. Another process in the art of making needles furnishes an
example of one of the simplest contrivances which can come under
the denomination of a tool. After the needles have been arranged
in the manner just described, it is necessary to separate them
into two parcels, in order that their points may be all in one
direction. This is usually done by women and children. The
needles are placed sideways in a heap, on a table, in front of
each operator, just as they are arranged by the process above
described. From five to ten are rolled towards this person with
the forefinger of the left hand; this separates them a very small
space from each other, and each in its turn is pushed lengthwise
to the right or to the left, according to the direction of the
point. This is the usual process, and in it every needle passes
individually under the finger of the operator. A small alteration
expedites the process considerably: the child puts on the
forefinger of its right hand a small cloth cap or fingerstall,
and rolling out of the heap from six to twelve needles, he keeps
them down by the forefinger of the left hand, whilst he presses
the forefinger of the right hand gently against their ends: those
which have the points towards the right hand stick into the
fingerstall; and the child, removing the finger of the left hand,
slightly raises the needles sticking into the cloth, and then
pushes them towards the left side. Those needles which had their
eyes on the right hand do not stick into the finger cover, and
are pushed to the heap on the right side before the repetition of
this process. By means of this simple contrivance each movement
of the finger, from one side to the other, carries five or six
needles to their proper heap; whereas, in the former method,
frequently only one was moved, and rarely more than two or three
were transported at one movement to their place.
13. Various operations occur in the arts in which the
assistance of an additional hand would be a great convenience to
the workman, and in these cases tools or machines of the simplest
structure come to our aid: vices of different forms, in which the
material to be wrought is firmly grasped by screws, are of this
kind, and are used in almost every workshop; but a more striking
example may be found in the trade of the nail-maker.
Some kinds of nails, such as those used for defending the
soles of coarse shoes, called hobnails, require a particular form
of the head, which is made by the stroke of a die. The workman
holds one end of the rod of iron out of which he forms the nails
in his left hand; with his right hand he hammers the red-hot end
of it into a point, and cutting the proper length almost off,
bends it nearly at a right angle. He puts this into a hole in a
small stake-iron immediately under a hammer which is connected
with a treadle, and has a die sunk in its surface corresponding
to the intended form of the head; and having given one part of
the form to the head with the small hammer in his hand, he moves
the treadle with his foot, disengages the other hammer, and
completes the figure of the head; the returning stroke produced
by the movement of the treadle striking the finished nail out of
the hole in which it was retained. Without this substitution of
his foot for another hand, the workman would, probably, be
obliged to heat the nails twice over.
14. Another, though fortunately a less general substitution
of tools for human hands, is used to assist the labour of those
who are deprived by nature, or by accident, of some of their
limbs. Those who have had an opportunity of examining the
beautiful contrivances for the manufacture of shoes by machinery,
which we owe to the fertile invention of Mr Brunel, must have
noticed many instances in which the workmen were enabled to
execute their task with precision, although labouring under the
disadvantages of the loss of an arm or leg. A similar instance
occurs at Liverpool, in the Institution for the Blind, where a
machine is used by those afflicted with blindness, for weaving
sash-lines; it is said to have been the invention of a person
suffering under that calamity. Other examples might be mentioned
of contrivances for the use, the amusement, or the instruction of
the wealthier classes, who labour under the same natural
disadvantages. These triumphs of skill and ingenuity deserve a
double portion of our admiration when applied to mitigate the
severity of natural or accidental misfortune; when they supply
the rich with occupation and knowledge; when they relieve the
poor from the additional evils of poverty and want.
15. Division of the objects of machinery. There exists a
natural, although, in point of number, a very unequal division
amongst machines: they may be classed as; first, those which are
employed to produce power, and as, secondly, those which are
intended merely to transmit force and execute work. The first of
these divisions is of great importance, and is very limited in
the variety of its species, although some of those species
consist of numerous individuals.
Of that class of mechanical agents by which motion is
transmitted--the lever, the pulley, the wedge, and many others--
it has been demonstrated, that no power is gained by their use,
however combined. Whatever force is applied at one point can only
be exerted at some other, diminished by friction and other
incidental causes; and it has been further proved, that whatever
is gained in the rapidity of execution is compensated by the
necessity of exerting additional force. These two principles,
long since placed beyond the reach of doubt, cannot be too
constantly borne in mind. But in limiting our attempts to things
which are possible, we are still, as we hope to shew, possessed
of a field of inexhaustible research, and of advantages derived
from mechanical skill, which have but just begun to exercise
their influence on our arts, and may be pursued without limit
contributing to the improvement, the wealth, and the happiness of
our race.
16. Of those machines by which we produce power, it may be
observed, that although they are to us immense acquisitions, yet
in regard to two of the sources of this power--the force of wind
and of water--we merely make use of bodies in a state of motion
by nature; we change the directions of their movement in order to
render them subservient to our purposes, but we neither add to
nor diminish the quantity of motion in existence. When we expose
the sails of a windmill obliquely to the gale, we check the
velocity of a small portion of the atmosphere, and convert its
own rectilinear motion into one of rotation in the sails; we thus
change the direction of force, but we create no power. The same
may be observed with regard to the sails of a vessel; the
quantity of motion given by them is precisely the same as that
which is destroyed in the atmosphere. If we avail ourselves of a
descending stream to turn a water-wheel, we are appropriating a
power which nature may appear, at first sight, to be uselessly
and irrecoverably wasting, but which, upon due examination, we
shall find she is ever regaining by other processes. The fluid
which is falling from a higher to a lower level, carries with it
the velocity due to its revolution with the earth at a greater
distance from its centre. It will therefore accelerate, although
to an almost infinitesimal extent, the earth's daily rotation.
The sum of all these increments of velocity, arising from the
descent of all the falling waters on the earth's surface, would
in time become perceptible, did not nature, by the process of
evaporation, convey the waters back to their sources; and thus
again, by removing matter to a greater distance from the centre,
destroy the velocity generated by its previous approach.
17. The force of vapour is another fertile source of moving
power; but even in this case it cannot be maintained that power
is created. Water is converted into elastic vapour by the
combustion of fuel. The chemical changes which thus take place
are constantly increasing the atmosphere by large quantities of
carbonic acid and other gases noxious to animal life. The means
by which nature decomposes these elements, or reconverts them
into a solid form, are not sufficiently known: but if the end
could be accomplished by mechanical force, it is almost certain
that the power necessary to produce it would at least equal that
which was generated by the original combustion. Man, therefore,
does not create power; but, availing himself of his knowledge of
nature's mysteries, he applies his talents to diverting a small
and limited portion of her energies to his own wants: and,
whether he employs the regulated action of steam, or the more
rapid and tremendous effects of gunpowder, he is only producing
on a small scale compositions and decompositions which nature is
incessantly at work in reversing, for the restoration of that
equilibrium which we cannot doubt is constantly maintained
throughout even the remotest limits of our system. The operations
of man participate in the character of their author; they are
diminutive, but energetic during the short period of their
existence: whilst those of nature, acting over vast spaces, and
unlimited by time, are ever pursuing their silent and resistless
career.
18. In stating the broad principle, that all combinations of
mechanical art can only augment the force communicated to the
machine at the expense of the time employed in producing the
effect, it might, perhaps, be imagined, that the assistance
derived from such contrivances is small. This is, however, by no
means the case: since the almost unlimited variety they afford,
enables us to exert to the greatest advantage whatever force we
employ. There is, it is true, a limit beyond which it is
impossible to reduce the power necessary to produce any given
effect, but it very seldom happens that the methods first
employed at all approach that limit. In dividing the knotted root
of a tree for fuel, how very different will be the time consumed,
according to the nature of the tool made use of! The hatchet, or
the adze, will divide it into small parts, but will consume a
large portion of the workman's time. The saw will answer the same
purpose more quickly and more effectually. This, in its turn, is
superseded by the wedge, which rends it in a still shorter time.
If the circumstances are favourable, and the workman skilful, the
time and expense may be still further reduced by the use of a
small quantity of gunpowder exploded in holes judiciously placed
in the block.
19. When a mass of matter is to be removed a certain force
must be expended; and upon the proper economy of this force the
price of transport will depend. A country must, however, have
reached a high degree of civilization before it will have
approached the limit of this economy. The cotton of Java is
conveyed in junks to the coast of China; but from the seed not
being previously separated, three-quarters of the weight thus
carried is not cotton. This might, perhaps, be justified in Java
by the want of machinery to separate the seed, or by the relative
cost of the operation in the two countries. But the cotton
itself, as packed by the Chinese, occupies three times the bulk
of an equal quantity shipped by Europeans for their own markets.
Thus the freight of a given quantity of cotton costs the Chinese
nearly twelve times the price to which, by a proper attention to
mechanical methods, it might be reduced. *
NOTES:
1. 'The Bandana handkerchiefs manufactured at Glasgow have long
superseded the genuine ones, and are now committed in large
quantities both by the natives and Chines.' Crawford's Indian
Archipelago, vol. iii, p. 505.
2. 'Captain Clapperton, when on a visit at the court of the
Sultan Bello, states, that provisionswere regularly sent me from
the sultan's table on pewter dishes with the London stamp; and I
even had a piece of meat served up on a white wash-hand basin of
English manufacture.' Clapperton's Journey, p. 88.
3. At Calicut, in the East Indies (whence the cotton cloth caled
calico derivesits name), the price of labour is one-seventh of
that in England, yet the market is supplied from British looms.
4. Liverpool, though not itself a manufacturing town, has been
placed in this list, from its connection with Manchester, of
which it is the port.
5. So sensible are the effects of grease in diminishing friction,
that the drivers of sledges in Amsterdam, on which heavy goodsare
transported, cary in their hand a rope soaked in tallow, which
they thrown down from time to time before the sledge, in order
that, by passing over the rope, it may become greased.
Chapter 2
Accumulating Power
20. Whenever the work to be done requires more force for its
execution than can be generated in the time necessary for its
completion, recourse must be had to some mechanical method of
preserving and condensing a part of the power exerted previously
to the commencement of the process. This is most frequently
accomplished by a fly-wheel, which is in fact nothing more than a
wheel having a very heavy rim, so that the greater part of its
weight is near the circumference. It requires great power applied
for some time to put this into rapid motion; but when moving with
considerable velocity, the effects are exceedingly powerful, if
its force be concentrated upon a small object. In some of the
iron works where the power of the steam-engine is a little too
small for the rollers which it drives, it is usual to set the
engine at work a short time before the red-hot iron is ready to
be removed from the furnace to the rollers, and to allow it to
work with great rapidity until the fly has acquired a velocity
rather alarming to those unused to such establishments. On
passing the softened mass of iron through the first groove, the
engine receives a great and very perceptible check; and its speed
is diminished at the next and at each succeeding passage, until
the iron bar is reduced to such a size that the ordinary power of
the engine is sufficient to roll it.
21. The powerful effect of a large flywheel when its force
can be concentrated on a point, was curiously illustrated at one
of the largest of our manufactories. The proprietor was shewing
to a friend the method of punching holes in iron plates for the
boilers of steam-engines. He held in his hand a piece of
sheet-iron three-eighths of an inch thick, which he placed under
the punch. Observing, after several holes had been made, that the
punch made its perforations more and more slowly, he called to
the engine-man to know what made the engine work so sluggishly,
when it was found that the flywheel and punching apparatus had
been detached from the steam-engine just at the commencement of
his experiment.
22. Another mode of accumulating power arises from lifting a
weight and then allowing it to fall. A man, even with a heavy
hammer, might strike repeated blows upon the head of a pile
without producing any effect. But if he raises a much heavier
hammer to a much greater height, its fall, though far less
frequently repeated, will produce the desired effect.
When a small blow is given to a large mass of matter, as to a
pile, the imperfect elasticity of the material causes a small
loss of momentum in the transmission of the motion from each
particle to the succeeding one; and, therefore, it may happen
that the whole force communicated shall be destroyed before it
reaches the opposite extremity.
23. The power accumulated within a small space by gunpowder
is well known; and, though not strictly an illustration of the
subject discussed in this chapter, some of its effects, under
peculiar circumstances, are so singular, that an attempt to
explain them may perhaps be excused. If a gun is loaded with ball
it will not kick so much as when loaded with small shot; and
amongst different kinds of shot, that which is the smallest,
causes the greatest recoil against the shoulder. A gun loaded
with a quantity of sand, equal in weight to a charge of
snipe-shot, kicks still more. If, in loading, a space is left
between the wadding and the charge, the gun either recoils
violently, or bursts. If the muzzle of a gun has accidentally
been stuck into the ground, so as to be stopped up with clay, or
even with snow, or if it be fired with its muzzle plunged into
water, the almost certain result is that it bursts.
The ultimate cause of these apparently inconsistent effects
is, that every force requires time to produce its effect; and if
the time requisite for the elastic vapour within to force out the
sides of the barrel, is less than that in which the condensation
of the air near the wadding is conveyed in sufficient force to
drive the impediment from the muzzle, then the barrel must burst.
If sometimes happens that these two forces are so nearly balanced
that the barrel only swells; the obstacle giving way before the
gun is actually burst.
The correctness of this explanation will appear by tracing
step by step the circumstances which arise on discharging a gun
loaded with powder confined by a cylindrical piece of wadding,
and having its muzzle filled with clay, or some other substance
having a moderate degree of resistance. In this case the first
effect of the explosion is to produce an enormous pressure on
everything confining it, and to advance the wadding through a
very small space. Here let us consider it as at rest for a
moment, and examine its condition. The portion of air in
immediate contact with the wadding is condensed; and if the
wadding were to remain at rest, the air throughout the tube would
soon acquire a uniform density. But this would require a small
interval of time; for the condensation next the wadding would
travel with the velocity of sound to the other end, from whence,
being reflected back, a series of waves would be generated,
which, aided by the friction of the tube, would ultimately
destroy the motion.
But until the first wave reaches the impediment at the
muzzle, the air can exert no pressure against it. Now if the
velocity communicated to the wadding is very much greater than
that of sound, the condensation of the air immediately in advance
of it may be very great before the resistance transmitted to the
muzzle is at all considerable; in which case the mutual repulsion
of the particles of air so compressed, will offer an absolute
barrier to the advance of the wadding.(1*)
If this explanation be correct, the additional recoil, when a
gun is loaded with small shot or sand, may arise in some measure
from the condensation of the air contained between their
particles; but chiefly from the velocity communicated by the
explosion to those particles of the substances in immediate
contact with the powder being greater than that with which a wave
can be transmitted through them. It also affords a reason for the
success of a method of blasting rocks by filling the upper part
of the hole above the powder with sand, instead of clay rammed
hard. That the destruction of the gun barrel does not arise from
the property possessed by fluids, and in some measure also by
sand and small shot, of pressing equally in all directions, and
thus exerting a force against a large portion of the interior
surface, seems to be proved by a circumstance mentioned by Le
Vaillant and other travellers, that, for the purpose of taking
birds without injuring their plumage, they filled the barrel of
their fowling pieces with water, instead of loading them with a
charge of shot.
24. The same reasoning explains a curious phenomenon which
occurs in firing a still more powerfully explosive substance. If
we put a small quantity of fulminating silver upon the face of an
anvil, and strike it slightly with a hammer, it explodes; but
instead of breaking either the hammer or the anvil, it is found
that that part of the face of each in contact with the
fulminating silver is damaged. In this case the velocity
communicated by the elastic matter disengaged may be greater than
the velocity of a wave traversing steel; so that the particles at
the surface are driven by the explosion so near to those next
adjacent, that when the compelling force is removed, the
repulsion of the particles within the mass drives back those
nearer to the surface, with such force, that they pass beyond the
limits of attraction, and are separated in the shape of powder.
25. i) The success of the experiment of firing a tallow candle
through a deal board, would be explained in the same manner, by
supposing the velocity of a wave propagated through deal to be
greater than that of a wave passing through tallow.
25. ii) The boiler of a steam-engine sometimes bursts even
during the escape of steam through the safety-valve. If the water
in the boiler is thrown upon any part which happens to be red
hot, the steam formed in the immediate neighbourhood of that part
expands with greater velocity than that with which a wave can be
transmitted through the less heated steam; consequently one
particle is urged against the next, and an almost invincible
obstacle is formed, in the same manner as described in the case
of the discharge of a gun. If the safety-valve is closed, it may
retain the pressure thus created for a short time, and even when
it is open the escape may not be sufficiently rapid to remove all
impediment; there may therefore exist momentarily within the
boiler pressures of various force, varying from that which can
just lift the safety-valve up to that which is sufficient, if
exerted during an extremely small space of time, to tear open the
boiler itself.
26. This reasoning ought, however, to be admitted with
caution; and perhaps some inducement to examine it carefully may
be presented by tracing it to extreme cases. It would seem, but
this is not a necessary consequence, that a gun might be made so
long, that it would burst although no obstacle filled up its
muzzle. It should also follow that if, after the gun is charged,
the air were extracted from the barrel, though the muzzle be then
left closed, the gun ought not to burst. It would also seem to
follow from the principle of the explanation, that a body might
be projected in air, or other elastic resisting medium, with such
force that, after advancing a very short space it should return
in the same direction in which it was projected.
NOTES:
1. See Poisson's remarks, Ecole Polytec. Cahier, xxi, p. 191.
Chapter 3
Regulating Power
27. Uniformity and steadiness in the rate at which machinery
works, are essential both for its effect and its duration. The
first illustration which presents itself is that beautiful
contrivance, the governor of the steam-engine, which must
immediately occur to all who are familiar with that admirable
engine. Wherever the increased speed of the engine would lead to
injurious or dangerous consequences, this is applied; and it is
equally the regulator of the water-wheel which drives a
spinning-jenny, or of the windmills which drain our fens. In the
dockyard at Chatham, the descending motion of a large platform,
on which timber is raised, is regulated by a governor; but as the
weight is very considerable, the velocity of this governor is
still further checked by causing its motion to take place in
water.
28. Another very beautiful contrivance for regulating the
number of strokes made by a steam-engine, is used in Cornwall: it
is called the cataract, and depends on the time required to fill
a vessel plunged in water, the opening of the valve through which
the fluid is admitted being adjustable at the will of the
engine-man.
29. The regularity of the supply of fuel to the fire under
the boilers of steam-engines is another mode of contributing to
the uniformity of their rate, and also economizes the consumption
of coal. Several patents have been taken out for methods of
regulating this supply: the general principle being to make the
engine supply the fire with small quantities of fuel at regular
intervals by means of a hopper, and to make it diminish this
supply when the engine works too quickly. One of the incidental
advantages of this plan is, that by throwing on a very small
quantity of coal at a time, the smoke is almost entirely
consumed. The dampers of ashpits and chimneys are also, in some
cases, connected with machines in order to regulate their speed.
30. Another contrivance for regulating the effect of
machinery consists in a vane or fly, of little weight, but
presenting a large surface. This revolves rapidly, and soon
acquires a uniform rate, which it cannot greatly exceed, because
any addition to its velocity produces a much greater addition to
the resistance it meets with from the air. The interval between
the strokes on the bell of a clock is regulated in this way, and
the fly is so contrived, that the interval may be altered by
presenting the arms of it more or less obliquely to the direction
in which they move. This kind of fly, or vane, is generally used
in the smaller kinds of mechanism, and, unlike the heavy fly, it
is a destroyer instead of a preserver of force. It is the
regulator used in musical boxes, and in almost all mechanical
toys.
31. The action of a fly, or vane, suggests the principle of
an instrument for measuring the altitude of mountains, which
perhaps deserves a trial, since, if it succeed only tolerably, it
will form a much more portable instrument than the barometer. It
is well known that the barometer indicates the weight of a column
of the atmosphere above it, whose base is equal to the bore of
the tube. It is also known that the density of the air adjacent
to the instrument will depend both on the weight of air above it,
and on the heat of the air at that place. If, therefore, we can
measure the density of the air, and its temperature, the height
of a column of mercury which it would support in the barometer
can be found by calculation. Now the thermometer gives
information respecting the temperature of the air immediately;
and its density might be ascertained by means of a watch and a
small instrument, in which the number of turns made by a vane
moved by a constant force, should be registered. The less dense
the air in which the vane revolves, the greater will be the
number of its revolutions in a given time: and tables could be
formed from experiments in partially exhausted vessels, aided by
calculation, from which, if the temperature of the air, and the
number of revolutions of the vane are given, the corresponding
height of the barometer might be found.(1*)
NOTES:
1. To persons who may be inclined to experiment upon this or any
other instrument, I would beg to suggest the perusal of the
section 'On the art of Observing', Observations on the Decline of
Science in England, p. 170, Fellowes, 1828.
Chapter 4
Increase and Diminution of Velocity
32. The fatigue produced on the muscles of the human frame
does not altogether depend on the actual force employed in each
effort, but partly on the frequency with which it is exerted. The
exertion necessary to accomplish every operation consists of two
parts: one of these is the expenditure of force which is
necessary to drive the tool or instrument; and the other is the
effort required for the motion of some limb of the animal
producing the action. In driving a nail into a piece of wood, one
of these is lifting the hammer, and propelling its head against
the nail; the other is, raising the arm itself, and moving it in
order to use the hammer. If the weight of the hammer is
considerable, the former part will cause the greatest portion of
the exertion. If the hammer is light, the exertion of raising the
arm will produce the greatest part of the fatigue. It does
therefore happen, that operations requiring very trifling force,
if frequently repeated, will tire more effectually than more
laborious work. There is also a degree of rapidity beyond which
the action of the muscles cannot be pressed.
33. The most advantageous load for a porter who carries wood
up stairs on his shoulders, has been investigated by M. Coulomb;
but he found from experiment that a man walking up stairs without
any load, and raising his burden by means of his own weight in
descending, could do as much work in one day, as four men
employed in the ordinary way with the most favourable load.
34. The proportion between the velocity with which men or
animals move, and the weights they carry, is a matter of
considerable importance, particularly in military affairs. It is
also of great importance for the economy of labour, to adjust the
weight of that part of the animal's body which is moved, the
weight of the tool it urges, and the frequency of repetition of
these efforts, so as to produce the greatest effect. An instance
of the saving of time by making the same motion of the arm
execute two operations instead of one, occurs in the simple art
of making the tags of bootlaces: these tags are formed out of
very thin, tinned, sheet-iron, and were formerly cut out of long
strips of that material into pieces of such a breadth that when
bent round they just enclosed the lace. Two pieces of steel have
recently been fixed to the side of the shears, by which each
piece of tinned-iron as soon as it is cut is bent into a
semi-cylindrical form. The additional power required for this
operation is almost imperceptible, and it is executed by the same
motion of the arm which produces the cut. The work is usually
performed by women and children; and with the improved tool more
than three times the quantity of tags is produced in a given
time.(1*)
35. Whenever the work is itself light, it becomes necessary,
in order to economize time, to increase the velocity. Twisting
the fibres of wool by the fingers would be a most tedious
operation: in the common spinning-wheel the velocity of the foot
is moderate, but by a very simple contrivance that of the thread
is most rapid. A piece of catgut passing round a large wheel, and
then round a small spindle, effects this change. This contrivance
is common to a multitude of machines, some of them very simple.
In large shops for the retail of ribands, it is necessary at
short intervals to 'take stock', that is, to measure and rewind
every piece of riband, an operation which, even with this mode of
shortening it, is sufficiently tiresome, but without it would be
almost impossible from its expense. The small balls of sewing
cotton, so cheap and so beautifully wound, are formed by a
machine on the same principle, and but a few steps more
complicated.
36. In turning from the smaller instruments in frequent use
to the larger and more important machines, the economy arising
from the increase of velocity becomes more striking. In
converting cast into wrought-iron, a mass of metal, of about a
hundredweight, is heated almost to white heat, and placed under a
heavy hammer moved by water or steam power. This is raised by a
projection on a revolving axis; and if the hammer derived its
momentum only from the space through which it fell, it would
require a considerably greater time to give a blow. But as it is
important that the softened mass of red-hot iron should receive
as many blows as possible before it cools, the form of the cam or
projection on the axis is such, that the hammer, instead of being
lifted to a small height, is thrown up with a jerk, and almost
the instant after it strikes against a large beam, which acts as
a powerful spring, and drives it down on the iron with such
velocity that by these means about double the number of strokes
can be made in a given time. In the smaller tilt-hammers, this is
carried still further by striking the tail of the tilt-hammer
forcibly against a small steel anvil, it rebounds with such
velocity, that from three to five hundred strokes are made in a
minute. In the manufacture of anchors, an art in which a similar
contrivance is of still greater importance, it has only been
recently applied.
37. In the manufacture of scythes, the length of the blade
renders it necessary that the workman should move readily, so as
to bring every part of it on the anvil in quick succession. This
is effected by placing him in a seat suspended by ropes from the
ceiling: so that he is enabled, with little bodily exertion, to
vary his distance, by pressing his feet against the block which
supports the anvil, or against the floor.
38. An increase of velocity is sometimes necessary to render
operations possible: thus a person may skate with great rapidity
over ice which would not support his weight if he moved over it
more slowly. This arises from the fact, that time is requisite
for producing the fracture of the ice: as soon as the weight of
the skater begins to act on any point, the ice, supported by the
water, bends slowly under him; but if the skater's velocity is
considerable, he has passed off from the spot which was loaded
before the bending has reached the point which would cause the
ice to break.
39. An effect not very different from this might take place
if very great velocity were communicated to boats. Let us suppose
a flatbottomed boat, whose bow forms an inclined plane with the
bottom, at rest in still water. If we imagine some very great
force suddenly to propel this boat, the inclination of the plane
at the forepart would cause it to rise in the water; and if the
force were excessive, it might even rise out of the water, and
advance, by a series of leaps, like a piece of slate or an oyster
shell, thrown as a 'duck and drake'.
If the force were not sufficient to pull the boat out of the
water, but were just enough to bring its bottom to the surface,
it would be carried along with a kind of gliding motion with
great rapidity; for at every point of its course it would require
a certain time before, it could sink to its usual draft of water;
but before that time had elapsed, it would have advanced to
another point, and consequently have been raised by the reaction
of the water on the inclined plane at its forepart.
40. The same fact, that bodies moving with great velocity
have not time to exert the full effect of their weight, seems to
explain a circumstance which appears to be very unaccountable. It
sometimes happens that when foot-passengers are knocked down by
carriages, the wheels pass over them with scarcely any injury,
though, if the weight of the carriage had rested on their body,
even for a few seconds, it would have crushed them to death. If
the view above taken is correct, the injury in such circumstances
will chiefly happen to that part of the body which is struck by
the advancing wheel.
41. An operation in which rapidity is of essential importance
is in bringing the produce of mines up to the surface. The shafts
through which the produce is raised are sunk at a very great
expense, and it is, of course, desirable to sink as few of them
as possible. The matter to be extracted is therefore raised by
steam-engines with considerable, and without this many of our
mines could not be worked velocity, with profit.
42. The effect of great velocity in modifying the form of a
cohesive substance is beautifully shown in the process for making
window glass, termed "flashing", which is one of the most striking
operations in our domestic arts. A workman having dipped his iron
tube into the glass pot, and loaded it with several pounds of the
melted "metal", blows out a large globe, which is connected with
his rod by a short thick hollow neck. Another workman now fixes
to the globe immediately opposite to its neck, an iron rod, the
extremity of which has been dipped in the melted glass; and when
this is firmly attached, a few drops of water separate the neck
of the globe from the iron tube. The rod with the globe attached
to it is now held at the mouth of a glowing furnace: and by
turning the rod the globe is made to revolve slowly, so as to be
uniformly exposed to the heat: the first effect of this softening
is to make the glass contract upon itself and to enlarge the
opening of the neck. As the softening proceeds, the globe is
turned more quickly on its axis, and when very soft and almost
incandescent, it is removed from the fire, and the velocity of
rotation being still continually increased, the opening enlarges
from the effect of the centrifugal force, at first gradually,
until at last the mouth suddenly expands or "flashes" out into one
large circular sheet of red hot glass. The neck of the original
globe, which is to become the outer part of the sheet, is left
thick to admit of this expansion, and forms the edge of the
circular plate of glass, which is called a "Table". The centre
presents the appearance of a thick boss or prominence, called the
"Bull's-eye", at the part by which it was attached to the iron
rod.
43. The most frequent reason for employing contrivances for
diminishing velocity, arises from the necessity of overcoming
great resistances with small power. Systems of pulleys, the
crane, and many other illustrations, might also be adduced here
as examples; but they belong more appropriately to some of the
other causes which we have assigned for the advantages of
machinery. The common smoke-jack is an instrument in which the
velocity communicated is too great for the purpose required, and
it is transmitted through wheels which reduce it to a more
moderate rate.
44. Telegraphs are machines for conveying information over
extensive lines with great rapidity. They have generally been
established for the purposes of transmitting information during
war, but the increasing wants of man will probably soon render
them subservient to more peaceful objects.
A few years since the telegraph conveyed to Paris information
of the discovery of a comet, by M. Gambart, at Marseilles: the
message arrived during a sitting of the French Board of
Longitude, and was sent in a note from the Minister of the
Interior to Laplace, the President, who received it whilst the
writer of these lines was sitting by his side. The object in this
instance was, to give the earliest publicity to the fact, and to
assure to M. Gambart the title of its first discoverer.
At Liverpool a system of signals is established for the
purposes of commerce, so that each merchant can communicate with
his own vessel long before she arrives in the port.
NOTES:
1. See Transactions of the Society of Arts, 1826.
Chapter 5
Extending the Time of Action of Forces
45. This is one of the most common and most useful of the
employments of machinery. The half minute which we daily devote
to the winding-up of our watches is an exertion of labour almost
insensible; yet, by the aid of a few wheels, its effect is spread
over the whole twenty-four hours. In our clocks, this extension
of the time of action of the original force impressed is carried
still further; the better kind usually require winding up once in
eight days, and some are occasionally made to continue in action
during a month, or even a year. Another familiar illustration may
be noticed in our domestic furniture: the common jack by which
our meat is roasted, is a contrivance to enable the cook in a few
minutes to exert a force which the machine retails out during the
succeeding hour in turning the loaded spit; thus enabling her to
bestow her undivided attention on the other important duties of
her vocation. A great number of automatons and mechanical toys
moved by springs, may be classed under this division.
46. A small moving power, in the shape of a jack or a spring
with a train of wheels, is often of great convenience to the
experimental philosopher, and has been used with advantage in
magnetic and electric experiments where the rotation of a disk of
metal or other body is necessary, thus allowing to the enquirer
the unimpeded use of both his hands. A vane connected by a train
of wheels, and set in motion by a heavy weight, has also, on some
occasions, been employed in chemical processes, to keep a
solution in a state of agitation. Another object to which a
similar apparatus may be applied, is the polishing of small
specimens of minerals for optical experiments.
Chapter 6
Saving time in Natural Operations
47. The process of tanning will furnish us with a striking
illustration of the power of machinery in accelerating certain
processes in which natural operations have a principal effect.
The object of this art is to combine a certain principle called
tanning with every particle of the skin to be tanned. This, in
the ordinary process, is accomplished by allowing the skins to
soak in pits containing a solution of tanning matter: they remain
in the pits six, twelve, or eighteen months; and in some
instances (if the hides are very thick), they are exposed to the
operation for two years, or even during a longer period. This
length of time is apparently required in order to allow the
tanning matter to penetrate into the interior of a thick hide.
The improved process consists in placing the hides with the
solution of tan in close vessels, and then exhausting the air.
The effect is to withdraw any air which may be contained in the
pores of the hides, and to aid capillary attraction by the
pressure of the atmosphere in forcing the tan into the interior
of the skins. The effect of the additional force thus brought
into action can be equal only to one atmosphere, but a further
improvement has been made: the vessel containing the hides is,
after exhaustion, filled up with a solution of tan; a small
additional quantity is then injected with a forcing-pump. By
these means any degree of pressure may be given which the
containing vessel is capable of supporting; and it has been found
that, by employing such a method, the thickest hides may be
tanned in six weeks or two months.
48. The same process of injection might be applied to
impregnate timber with tar, or any other substance capable of
preserving it from decay, and if it were not too expensive, the
deal floors of houses might thus be impregnated with alumine or
other substances, which would render them much less liable to be
accidentally set on fire. In some cases it might be useful to
impregnate woods with resins, varnish, or oil; and wood saturated
with oil might, in some instances, be usefully employed in
machinery for giving a constant, but very minute supply of that
fluid to iron or steel, against which it is worked. Some idea of
the quantity of matter which can be injected into wood by great
pressure, may be formed, from considering the fact stated by Mr
Scoresby, respecting an accident which occurred to a boat of one
of our whaling-ships. The harpoon having been struck into the
fish, the whale in this instance, dived directly down, and
carried the boat along with him. On returning to the surface the
animal was killed, but the boat, instead of rising, was found
suspended beneath the whale by the rope of the harpoon; and on
drawing it up, every part of the wood was found to be so
completely saturated with water as to sink immediately to the
bottom.
49. The operation of bleaching linen in the open air is one
for which considerable time is necessary; and although it does
not require much labour, yet, from the risk of damage and of
robbery from long /exposure, a mode of shortening the process was
highly desirable. The method now practised, although not
mechanical, is such a remarkable instance of the application of
science to the practical purposes of manufactures, that in
mentioning the advantages derived from shortening natural
operations, it would have been scarcely pardonable to have
omitted all allusion to the beautiful application of chlorine, in
combination with lime, to the art of bleaching.
50. Another instance more strictly mechanical occurs in some
countries where fuel is expensive, and the heat of the sun is not
sufficient to evaporate the water from brine springs. The water
is first pumped up to a reservoir, and then allowed to fall in
small streams through faggots. Thus it becomes divided; and,
presenting a large surface, evaporation is facilitated, and the.
brine which is collected in the vessels below the faggots is
stronger than that which was pumped up. After thus getting rid of
a large part of the water, the remaining portion is driven off by
boiling. The success of this process depends on the condition of
the atmosphere with respect to moisture. If the air, at the time
the brine falls through the faggots, holds in solution as much
moisture as it can contain in an invisible state, no more can be
absorbed from the salt water, and the labour expended in pumping
is entirely wasted. The state of the air, as to dryness, is
therefore an important consideration in fixing the time when this
operation is to be performed; and an attentive examination of its
state, by means of the hygrometer, might be productive of some
economy of labour.
51. In some countries, where wood is scarce, the evaporation
of salt water is carried on by a large collection of ropes which
are stretched perpendicularly. In passing down the ropes, the
water deposits the sulphate of lime which it held in solution,
and gradually incrusts them, so that in the course of twenty
years, when they are nearly rotten, they are still sustained by
the surrounding incrustation, thus presenting the appearance of a
vast collection of small columns.
52. Amongst natural operations perpetually altering the
surface of our globe, there are some which it would be
advantageous to accelerate. The wearing down of the rocks which
impede the rapids of navigable rivers, is one of this class. A
very beautiful process for accomplishing this object has been
employed in America. A boat is placed at the bottom of the rapid,
and kept in its position by a long rope which is firmly fixed on
the bank of the river near the top. An axis, having a wheel
similar to the paddle-wheel of a steamboat fixed at each end of
it, is placed across the boat; so that the two wheels and their
connecting axis shall revolve rapidly, being driven by the force
of the passing current. Let us now imagine several beams of wood
shod with pointed iron fixed at the ends of strong levers,
projecting beyond the bow of the boat, as in the annexed
representation.
If these levers are at liberty to move up and down, and if
one or more projecting pieces, called cams, are fixed on the axis
opposite to the end of each lever, the action of the stream upon
the wheels will keep up a perpetual succession of blows. The
sharp-pointed shoe striking upon the rock at the bottom, will
continually detach small pieces, which the stream will
immediately carry off. Thus, by the mere action of the river
itself, a constant and most effectual system of pounding the rock
at its bottom is established. A single workman may, by the aid of
a rudder, direct the boat to any required part of the stream; and
when it is necessary to move up the rapid, as the channel is cut,
he can easily cause the boat to advance by means of a capstan.
53. When the object of the machinery just described has been
accomplished, and the channel is sufficiently deep, a slight
alteration converts the apparatus to another purpose almost
equally advantageous. The stampers and the projecting pieces on
the axis are removed, and a barrel of wood or metal, surrounding
part of the axis, and capable, at pleasure, of being connected
with, or disconnected from the axis itself, is substituted. The
rope which hitherto fastened the boat, is now fixed to this
barrel; and if the barrel is loose upon the axis, the
paddle-wheel makes the axis only revolve, and the boat remains in
its place: but the moment the axis is attached to its surrounding
barrel, this begins to turn, and winding up the rope, the boat is
gradually drawn up against the stream; and may be employed as a
kind of tug-boat for vessels which have occasion to ascend the
rapid. When the tug-boat reaches the summit the barrel is
released from the axis, and friction being applied to moderate
its velocity, the boat is allowed to descend.
54. Clocks occupy a very high place amongst instruments by
means of which human time is economized: and their multiplication
in conspicuous places in large towns is attended with many
advantages. Their position, nevertheless, in London, is often
very ill chosen; and the usual place, halfway up on a high
steeple, in the midst of narrow streets, in a crowded city, is
very unfavourable, unless the church happen to stand out from the
houses which form the street. The most eligible situation for a
clock is, that it should project considerably into the street at
some elevation, with a dial-plate on each side, like that which
belonged to the old church of St Dunstan, in Fleet Street, so
that passengers in both directions would have their attention
directed to the hour.
55. A similar remark applies, with much greater force, to the
present defective mode of informing the public of the position of
the receiving houses for the twopenny and general post. In the
lowest corner of the window of some attractive shop is found a
small slit, with a brass plate indicating its important office so
obscurely that it seems to be an object rather to prevent its
being conspicuous. No striking sign assists the anxious enquirer,
who, as the moments rapidly pass which precede the hour of
closing, torments the passenger with his enquiries for the
nearest post-office. He reaches it, perhaps, just as it is
closed; and must then either hasten to a distant part of the town
in order to procure the admission of his letters or give up the
idea of forwarding them by that post; and thus, if they are
foreign letters, he may lose, perhaps, a week or a fortnight by
waiting for the next packet.
The inconvenience in this and in some other cases, is of
perpetual and everyday occurrence; and though, in the greater
part of the individual cases, it may be of trifling moment, the
sum of all these produces an amount, which it is always worthy of
the government of a large and active population to attend to. The
remedy is simple and obvious: it would only be necessary, at each
letter-box, to have a light frame of iron projecting from the
house over the pavement, and carrying the letters G. P., or T.
P., or any other distinctive sign. All private signs are at
present very properly prohibited from projecting into the street:
the passenger, therefore, would at once know where to direct his
attention, in order to discover a post-office; and those
letter-boxes which occurred in the great thoroughfares could not
fail to be generally known.
Chapter 7
Exerting Forces Too Great for Human Power, and Executing
Operations Too Delicate for Human Touch
56. It requires some skill and a considerable apparatus to
enable many men to exert their whole force at a given point; and
when this number amounts to hundreds or to thousands, additional
difficulties present themselves. If ten thousand men were hired
to act simultaneously, it would be exceedingly difficult to
discover whether each exerted his whole force, and consequently,
to be assured that each man did the duty for which he was paid.
And if still larger bodies of men or animals were necessary, not
only would the difficulty of directing them become greater, but
the expense would increase from the necessity of transporting
food for their subsistence.
The difficulty of enabling a large number of men to exert
their force at the same instant of time has been almost obviated
by the use of sound. The whistle of the boatswain performs this
service on board ships; and in removing, by manual force, the
vast mass of granite, weighing above 1,400 tons, on which the
equestrian figure of Peter the Great is placed at St Petersburgh,
a drummer was always stationed on its summit to give the signal
for the united efforts of the workmen.
An ancient Egyptian drawing was discovered a few years since,
by Champollion, in which a multitude of men appeared harnessed to
a huge block of stone, on the top of which stood a single
individual with his hands raised above his head, apparently in
the act of clapping them, for the purpose of insuring the
exertion of their combined force at the same moment of time.
57. In mines, it is sometimes necessary to raise or lower
great weights by capstans requiring the force of more than one
hundred men. These work upon the surface; but the directions must
be communicated from below, perhaps from the depth of two hundred
fathoms. This communication, however, is accomplished with ease
and certainty by signals: the usual apparatus is a kind of
clapper placed on the surface close to the capstan, so that every
man may hear, and put in motion from below by a rope passing up
the shaft.
At Wheal Friendship mine in Cornwall, a different contrivance
is employed: there is in that mine an inclined plane, passing
underground about two-thirds of a mile in length. Signals are
communicated by a continuous rod of metal, which being struck
below, the blow is distinctly heard on the surface.
58. In all our larger manufactories numerous instances occur
of the application of the power of steam to overcome resistances
which it would require far greater expense to surmount by means
of animal labour. The twisting of the largest cables, the
rolling, hammering, and cutting large masses of iron, the
draining of our mines, all require enormous exertions of physical
force continued for considerable periods of time. Other means are
had recourse to when the force required is great, and the space
through which it is to act is small. The hydraulic press of
Bramah can, by the exertion of one man, produce a pressure of
1,500 atmospheres; and with such an instrument a hollow cylinder
of wrought iron three inches thick has been burst. In rivetting
together the iron plates, out of which steam-engine boilers are
made, it is necessary to produce as close a joint as possible.
This is accomplished by using the rivets red-hot: while they are
in that state the two plates of iron are rivetted together, and
the contraction which the rivet undergoes in cooling draws them
together with a force which is only limited by the tenacity of
the metal of which the rivet itself is made.
59. It is not alone in the greater operations of the engineer
or the manufacturer, that those vast powers which man has called
into action, in availing himself of the agency of steam, are
fully developed. Wherever the individual operation demanding
little force for its own performance is to be multiplied in
almost endless repetition, commensurate power is required. It is
the same 'giant arm' which twists 'the largest cable', that spins
from the cotton plant an 'almost gossamer thread'. Obedient to
the hand which called into action its resistless powers, it
contends with the ocean and the storm, and rides triumphant
through dangers and difficulties unattempted by the older modes
of navigation. It is the same engine that, in its more regulated
action, weaves the canvas it may one day supersede, or, with
almost fairy fingers, entwines the meshes of the most delicate
fabric that adorns the female form.(1*)
60. The Fifth Report of the Select Committee of the House of
Commons on the Holyhead Roads furnishes ample proof of the great
superiority of steam vessels. The following extracts are taken
from the evidence of Captain Rogers, the commander of one of the
packets:
Question. Are you not perfectly satisfied, from the experience
you have had, that the steam vessel you command is capable of
performing what no sailing vessel can do?
Answer. Yes.
Question. During your passage from Gravesend to the Downs, could
any square-rigged vessel, from a first-rate down to a sloop of
war, have performed the voyage you did in the time you did it in
the steamboat?
Answer. No: it was impossible. In the Downs we passed several
Indiamen, and 150 sail there that could not move down the
channel: and at the back of Dungeness we passed 120 more.
Question. At the time you performed that voyage, with the weather
you have described, from the Downs to Milford, if that weather
had continued twelve months, would any square-rigged vessel have
performed it?
Answer. They would have been a long time about it: probably,
would have been weeks instead of days. A sailing vessel would not
have beat up to Milford, as we did, in twelve months.
61. The process of printing on the silver paper, which is
necessary for bank-notes, is attended with some inconvenience,
from the necessity of damping the paper previously to taking the
impression. It was difficult to do this uniformly and in the old
process of dipping a parcel of several sheets together into a
vessel of water, the outside sheets becoming much more wet than
the others, were very apt to be torn. A method has been adopted
at the Bank of Ireland which obviates this inconvenience. The
whole quantity of paper to be damped is placed in a close vessel
from which the air is exhausted; water is then admitted, and
every leaf is completely wetted; the paper is then removed to a
press, and all the superfluous moisture is squeezed out.
62. The operation of pulverizing solid substances and of
separating the powders of various degrees of fineness, is common
in the arts: and as the best graduated sifting fails in effecting
this separation with sufficient delicacy, recourse is had to
suspension in a fluid medium. The substance when reduced by
grinding to the finest powder is agitated in water which is then
drawn off: the coarsest portion of the suspended matter first
subsides, and that which requires the longest time to fall down
is the finest. In this manner even emery powder, a substance of
great density, is separated into the various degrees of fineness
which are required. Flints, after being burned and ground, are
suspended in water, in order to mix them intimately with clay,
which is also suspended in the same fluid for the formation of
porcelain. The water is then in part evaporated by heat, and the
plastic compound, out of which our most beautiful porcelain is
formed, remains. It is a curious fact, and one which requires
further examination than it has yet received, that, if this
mixture be suffered to remain long at rest before it is worked
up, it becomes useless; for it is then found that the silex,
which at first was uniformly mixed, becomes aggregated together
in small lumps. This parallel to the formation of flints in the
chalk strata deserves attention.(2*)
63. The slowness with which powders subside, depends partly
on the specific gravity of the substance, and partly on the
magnitude of the particles themselves. Bodies, in falling through
a resisting medium, after a certain time acquire a uniform
velocity, which is called their terminal velocity, with which
they continue to descend: when the particles are very small, and
the medium dense, as water, this terminal velocity is soon
arrived at. Some of the finer powders even of emery require
several hours to subside through a few feet of water, and the mud
pumped up into our cisterns by some of the water companies is
suspended during a still longer time. These facts furnish us with
some idea of the great extent over which deposits of river mud
may be spread; for if the mud of any river whose waters enter the
Gulf Stream, sink through one foot in an hour, it might be
carried by that stream 1,500 miles before it had sunk to the
depth of 600 or 700 feet.
64. A number of small filaments of cotton project from even
the best spun thread, and when this thread is woven into muslin
they injure its appearance. To cut these off separately is quite
impossible, but they are easily removed by passing the muslin
rapidly over a cylinder of iron kept at a dull red heat: the time
during which each portion of the muslin is in contact with the
red-hot iron is too short to heat it to the burning point; but
the filaments being much finer, and being pressed close to the
hot metal, are burnt.
The removal of these filaments from patent net is still more
necessary for its perfection. The net is passed at a moderate
velocity through a flame of gas issuing from a very long and
narrow slit. Immediately above the flame a long funnel is fixed,
which is connected with a large air-pump worked by a
steam-engine. The flame is thus drawn forcibly through the net,
and all the filaments on both sides of it are burned off at one
operation. Previously to this application of the air-pump, the
net acting in the same way, although not to the same extent, as
the wire-gauze in Davy's safety lamp, cooled down the flame so as
to prevent the combustion of the filaments on the upper side: the
air-pump by quickening the current of ignited gas, removes this
inconvenience.
NOTES:
1. The importance and diversified applications of the steam
engine were most ably enforced in the speeches made at a public
meeting held (June 1824) for the purpose of proposing the
erection of a monument to the memory of James Watt; these were
subsequently printed.
2. Some observations on the subject, by Dr Fitton, occur in the
appendix to Captain King's Survey of the Coast of Australia, vol.
ii, p. 397. London, 1826.
Chapter 8
Registering Operations
65. One great advantage which we may derive from machinery is
from the check which it affords against the inattention, the
idleness, or the dishonesty of human agents. Few occupations are
more wearisome than counting a series of repetitions of the same
fact; the number of paces we walk affords a tolerably good
measure of distance passed over, but the value of this is much
enhanced by possessing an instrument, the pedometer, which will
count for us the number of steps we have made. A piece of
mechanism of this kind is sometimes applied to count the number
of turns made by the wheel of a carriage, and thus to indicate
the distance travelled: an instrument, similar in its object,
but differing in its construction, has been used for counting the
number of strokes made by a steam-engine, and the number of coins
struck in a press. One of the simplest instruments for counting
any series of operations, was contrived by Mr Donkin.(1*)
66. Another instrument for registering is used in some
establishments for calendering and embossing. Many hundred
thousand yards of calicoes and stuffs undergo these operations
weekly; and as the price paid for the process is small, the value
of the time spent in measuring them would bear a considerable
proportion to the profit. A machine has, therefore, been
contrived for measuring and registering the length of the goods
as they pass rapidly through the hands of the operator, by which
all chance of erroneous counting is avoided.
67. Perhaps the most useful contrivance of this kind, is one
for ascertaining the vigilance of a watchman. It is a piece of
mechanism connected with a clock placed in an apartment to which
the watchman has not access; but he is ordered to pull a string
situated in a certain part of his round once in every hour. The
instrument, aptly called a tell-tale, informs the owner whether
the man has missed any, and what hours during the night.
68. It is often of great importance, both for regulations of
excise as well as for the interest of the proprietor, to know the
quantity of spirits or of other liquors which have been drawn off
by those persons who are allowed to have access to the vessels
during the absence of the inspectors or principals. This may be
accomplished by a peculiar kind of stop-cock--which will, at
each opening, discharge only a certain measure of fluid the
number of times the cock has been turned being registered by a
counting apparatus accessible only to the master.
69. The time and labour consumed in gauging the contents of
casks partly filled, has led to an improvement which, by the
simplest means, obviates a considerable inconvenience, and
enables any person to read off, on a scale, the number of gallons
contained in any vessel, as readily as he does the degree of heat
indicated by his thermometer. A small stop-cock connects the
bottom of the cask with a glass tube of narrow bore fixed to a
scale on the side of the cask, and rising a little above its top.
The plug of the cock may be turned into three positions: in the
first, it cuts off all communication with the cask: in the
second, it opens a communication between the cask and the glass
tube: and, in the third. It cuts off the connection between the
cask and the tube, and opens a communication between the tube and
any vessel held beneath the cock to receive its contents. The
scale of the tube is graduated by pouring into the cask
successive quantities of water, while the communication between
the cask and the tube is open. Lines are then drawn on the scale
opposite the places in the tube to which the water rises at each
addition, and the scale being thus formed by actual
measurement,(2*) the contents of each cask are known by
inspection, and the tedious process of gauging is altogether
dispensed with. Other advantages accrue from this simple
contrivance, in the great economy of time which it introduces in
making mixtures of different spirits, in taking stock, and in
receiving spirit from the distiller.
70. The gas-meter, by which the quantity of gas used by each
consumer is ascertained, is another instrument of this kind. They
are of various forms, but all of them intended to register the
number of cubic feet of gas which has been delivered. It is very
desirable that these meters should be obtainable at a moderate
price, and that every consumer should employ them; because, by
making each purchaser pay only for what he consumes, and by
preventing that extravagant waste of gas which we frequently
observe, the manufacturer of gas will be enabled to make an equal
profit at a diminished price to the consumer.
71. The sale of water by the different companies in London,
might also, with advantage, be regulated by a meter. If such a
system were adopted, much water which is now allowed to run to
waste would be saved, and an unjust inequality between the rates
charged on different houses by the same company be avoided.
72. Another most important object to which a meter might be
applied, would be to register the quantity of water passing into
the boilers of steam-engines. Without this, our knowledge of the
quantity evaporated by different boilers, and with fireplaces of
different constructions, as well as our estimation of the duty of
steam-engines, must evidently be imperfect.
73. Another purpose to which machinery for registering
operations is applied with much advantage is the determination of
the average effect of natural or artificial agents. The mean
height of the barometer, for example, is ascertained by noting
its height at a certain number of intervals during the
twenty-four hours. The more these intervals are contracted, the
more correctly will the mean be ascertained; but the true mean
ought to be influenced by each momentary change which has
occurred. Clocks have been proposed and made with this object, by
which a sheet of paper is moved, slowly and uniformly, before a
pencil fixed to a float upon the surface of the mercury in the
cup of the barometer. Sir David Brewster proposed, several years
ago to suspend a barometer, and swing it as a pendulum. The
variations in the atmosphere would thus alter the centre of
oscillation, and the comparison of such an instrument with a good
clock, would enable us to ascertain the mean altitude of the
barometer during any interval of the observer's absence.(3*)
An instrument for measuring and registering the quantity of
rain, was invented by Mr John Taylor, and described by him in the
Philosophical Magazine. It consists of an apparatus in which a
vessel that receives the rain falling into the reservoir tilts
over as soon as it is full, and then presents another similar
vessel to be filled, which in like manner, when full, tilts the
former one back again. The number of times these vessels are
emptied is registered by a train of wheels; and thus, without the
presence of the observer, the quantity of rain falling during a
whole year may be measured and recorded.
Instruments might also be contrived to determine the average
force of traction of horses--of the wind--of a stream or of any
irregular and fluctuating effort of animal or other natural
force.
74. Clocks and watches may be considered as instruments for
registering the number of vibrations performed by a pendulum or a
balance. The mechanism by which these numbers are counted is
technically called a scapement. It is not easy to describe: but
the various contrivances which have been adopted for this
purpose, are amongst the most interesting and most ingenious to
which mechanical science has given birth. Working models, on an
enlarged scale, are almost necessary to make their action
understood by the unlearned reader; and, unfortunately, these are
not often to be met with. A very fine collection of such models
exists amongst the collection of instruments at the University of
Prague.
Instruments of this kind have been made to extend their
action over considerable periods of time, and to register not
merely the hour of the day, but the days of the week, of the
month, of the year, and also to indicate the occurrence of
several astronomical phenomena.
Repeating clocks and watches may be considered as instruments
for registering time, which communicate their information only
when the owner requires it, by pulling a string, or by some
similar application.
An apparatus has recently been applied to watches, by which
the hand which indicates seconds leaves a small dot of ink on the
dial-plate whenever a certain stop or detent is pushed in. Thus,
whilst the eye is attentively fixed on the phenomenon to be
observed, the finger registers on the face of the watch-dial the
commencement and the end of its appearance.
75. Several instruments have been contrived for awakening the
attention of the observer at times previously fixed upon. The
various kinds of alarums connected with clocks and watches are of
this kind. In some instances it is desirable to be able to set
them so as to give notice at many successive and distant points
of time, such as those of the arrival of given stars on the
meridian. A clock of this kind is used at the Royal Observatory
at Greenwich.
76. An earthquake is a phenomenon of such frequent occurrence,
and so interesting, both from its fearful devastations as well as
from its connection with geological theories, that it becomes
important to possess an instrument which shall, if possible,
indicate the direction of the shock, as well as its intensity.
An observation made a few years since at Odessa, after an
earthquake which happened during the night, suggests a simple
instrument by which the direction of the shock may be determined.
A glass vase, partly filled with water, stood on the table of
a room in a house at Odessa; and, from the coldness of the glass,
the inner part of the vessel above the water was coated with dew.
Several very perceptible shocks of an earthquake happened between
three and four o'clock in the morning; and when the observer got
up, he remarked that the dew was brushed off at two opposite
sides of the glass by a wave which the earthquake had caused in
the water. The line joining the two highest points of this wave
was, of course, that in which the shock travelled. This
circumstance, which was accidentally noticed by an engineer at
Odessa,(4*) suggests the plan of keeping, in countries subject to
earthquakes, glass vessels partly filled with treacle, or some
unctuous fluid, so that when any lateral motion is communicated
to them from the earth, the adhesion of the liquid to the glass
shall enable the observer, after some interval of time, to
determine the direction of the shock.
In order to obtain some measure of the vertical oscillation
of the earth, a weight might be attached to a spiral spring, or a
pendulum might be sustained in a horizontal position, and a
sliding index be moved by either of them, so that the extreme
deviations should be indicated by it. This, however, would not
give even the comparative measure accurately, because a
difference in the velocity of the rising or falling of the
earth's surface would affect the instrument.
NOTES:
1. Transactions of the Society of Arts, 1819, p. 116.
2. The contrivance is due to Mr Hencky, of High Holborn, in whose
establishment it is in constant use.
3. About seven or eight years since, without being aware of Sir
David Brewster's proposal. I adapted a barometer, as a pendulum,
to the works of a common eight day clock: it remained in my
library for several months, but I have mislaid the observations
which were made.
4. Memoires de l'Academie des Sciences de Petersburgh, 6e serie,
tom. i. p. 4.
Chapter 9
Economy of the Materials Employed
77. The precision with which all operations by machinery are
executed, and the exact similarity of the articles thus made,
produce a degree of economy in the consumption of the raw
material which is, in some cases, of great importance. The
earliest mode of cutting the trunk of a tree into planks, was by
the use of the hatchet or the adze. It might, perhaps, be first
split into three or four portions, and then each portion was
reduced to a uniform surface by those instruments. With such
means the quantity of plank produced would probably not equal the
quantity of the raw material wasted by the process: and, if the
planks were thin, would certainly fall far short of it. An
improved tool, completely reverses the case: in converting a tree
into thick planks, the saw causes a waste of a very small
fractional part; and even in reducing it to planks of only an
inch in thickness, does not waste more than an eighth part of the
raw material. When the thickness of the plank is still further
reduced, as is the case in cutting wood for veneering, the
quantity of material destroyed again begins to bear a
considerable proportion to that which is used; and hence circular
Back to Full Books
|