MECHANICAL ARTS. 
6 13 
3 edge of the experimental or practical geometry. Fric¬ 
tion, for inftance, after all the calculation that has been 
made, remains a matter of praBical mathematics ; the 
knowledge of which alone is of vaft importance ; for many 
wretched machines have been planned by people who 
have fuppoled that levers, wheels, pulleys, and ropes, 
would aCt in a machine as they are calculated upon paper ; 
and who, never having put their hand to labour, never 
knew the difference in effeCt between a machine and a 
drawing of one. Another observation arifes naturally 
from the fubjeCt ; that there are machines which will an- 
fwer upon a fmall fcale, but not upon a large one, and 
vice verfd. Among thofe which will anfwer only upon a 
great fcale, we imift reckon fuch machines whofe effect 
depends chiefly upon the weight of their parts or mate¬ 
rials, or on the violent affion of a body of water, or of 
fome other elaltic body : make a fmall model of fuch a 
machine, the weight of the parts becomes nothing, the 
affion of a fluid is fcarcely perceptible, the powers difap- 
pear which fhould have produced the eff'eff, and the ma¬ 
chine is ufelefs. There is a maximum in the dimenfions 
of every machine beyond or fhort of which it cannot pro¬ 
duce its fulfeft effeCt. But it will be afked, how are thefe 
precife dimenfions to be determined ? what is to be the 
exact bignefs of an excellent time-piece, a perfeCt mill, a 
veffel of the heft poffible condruCtion ? To folve thefe 
problems we mult unite the experimental or practical geo¬ 
metry of many ages with the pureft intellectual geometry : 
for nothing fatistaftory can be produced on the fubjeft 
by either of them apart, nor without great difficulty by 
their united ftrength. 
Thus, then, we fee that an art confifts in theory and 
practice : theory is merely an inoperative knowledge of 
the rules of the art; practice is the habitual and we may 
fay unconfcious ufe and application of thofe rules. It is 
difficult, not to fay impoffible, to proceed far in practice 
without theory, and equally fo to be perfeCt in theory 
without joining practice thereto. In every art there is a 
number of circuinftances relating to materials, tools, in¬ 
struments, and manual -dexterity, which only ufe can 
teach. Practice ffiows the difficulties, and produces the 
effcft; theory explains the phenomena, and removes the 
difficulties; whence it happens that none but well-in¬ 
formed and enlightened artills can well explain their own 
art. 
The language of the mechanical arts is very imperfeft 
on two accounts : the want of proper words, and the 
abundance of fynonymes. Some tools have federal dif¬ 
ferent names ; while others have only the generic name, 
as engine, machine, See. without any addition to mark the 
kind or fptcies of machine fpoken of; fometimes the 
flighted; difference will occafion workmen to abandon the 
generic name, and invent a new one; at other times, a 
tool lingular in its fhape and ufe has either no name at 
all, or bears the name of another to which it bears no 
Similarity. It were to be wifhed that more attention 
might be paid to the analogy of ffiape and application. 
Geometricians have not fo many names as figures; but, 
in the language of the arts, a hammer, pincers, a trough, 
a fhovel, & c. have ahnoft as many names as there are arts. 
Each manufaClure has a different language. Yet we are 
convinced, that the moll curious work, the molt compli¬ 
cated machinery, might be explained by a fmall number 
of known and familiar terms, if terms of art were ufed 
only to exprefs particular relations. This remark will 
not appear extravagant, when we confider, that complex 
machines are but combinations of fimple ones, that the 
Pimple machines are few in number; that in the expofi- 
tion of any manual operation, all the motions are redu¬ 
cible, with very little variation, to the rectilinear and the 
curvilinear. It were to be wifhed, then, that fome good 
logician, familiar with the arts, would undertake the ele¬ 
ments of a Grammar of the Ails. The fird Hep he muff 
take, would be to lettle the meaning or extent of certain 
«u-relative terms, as great, large, middling, thin, thick, weak, 
fmall, light, heavy. See. The fecorrd would be, to detdrv 
mine upon the difference or the refembiance between one 
indrument and another, one operation and another, whe- 
ther to leave them the fame names, or to give them fepa- 
rate ones. Whoever were to undertake fuch a talk would, 
we doubt not, find fewer new terms to introduce than 
fynonymes to retrench ; more difficulty in properly de¬ 
fining common things, fuch as a knot in lace-making, 
creux or hollow in feveral arts, than in explaining the molt 
complicated machinery. It is the want of correct defi¬ 
nitions, and the multitude, but not the diverfity, of mo¬ 
tions in manual operations, that make it fo difficult to 
write or fpeak clearly upon the arts. There is no re¬ 
medy for the fecond inconvenience but by becoming fa¬ 
miliar with the arts themfelves, which will amply repay 
our labour, whether by the advantages to be derived from 
them, or by the honour they do to the human mind. In 
what fyftem of phyfics or of metaphyfics is there more 
fagacity, intelligence, and curious refult, than in the ma¬ 
chines for drawing gold wire, making dockings, or in the 
trade of lace-makers, gauze-makers, weavers of cloth or 
of fi lk ? What demondration in the mathematics is more 
complicated than the mechanifm of fome time-pieces, or 
the different operation ufed upon hemp,or upon the cod of 
the filk-worm, before a thread fit for ufe can be produced ? 
Let us briefly notice three inventions of which the an¬ 
cients were intirely ignorant; and of which, to the dif- 
grace of modern hiltorians and poets, the names of the 
inventors are fcarcely known : the art of printing, the 
difeovery of gunpowder, and of the property of the mag¬ 
netic needle. What a revolution have thefe difeoveries 
occafioned in the republic of letters, in the military art, 
and in navigation 1 The magnet has conduced our vef- 
fels to the mod unexplored regions; printing has efta- 
bliffied a permanent correfpondence between the learned 
of every place, and of all ages to come ; and gunpowder 
lias reduced the art of war to certain principles. Thus 
thefe three arts have changed the face of nearly the whole 
habitable globe. 
How cautious fhould we be of undervaluing an inven¬ 
tion, or rejecting it as ufelefs, becaufe all its advantages 
do not immediately appear! It is much eafier to improve 
than to invent. Would not Montaigne blufh, could he 
,now come again among us, for having written, in 1580, 
“ that fire-anns were of fo little effeCt, except adoniffiing 
the ear, to which we are prefently accudomed, that it is 
to be hoped they will foon be laid afide.” Montaigne 
was a philofbpher upon fome occafions; he would have 
fliown more fagacity, however, upon this occafion, had he 
incited the artids of his day to the improvement of the 
awkward matchlocks and harquebufes ; or had he pre¬ 
dicted the invention and perfecting of machines which 
fhould give gunpowder its greated effect. Put Bacon in 
the place of Montaigne, and you will behold him conft- 
dering the matter with the eye of a philofbpher, and pre¬ 
dicting as it were the invention of grenades, mines, can¬ 
nons, bombs, and all the apparatus of military pyrotechny. 
But Montaigne is not the only philofopher who has judged 
too precipitately of the poflibility or impoffibility of cer¬ 
tain events or inventions. Defcartes, that extraordinary 
genius, born equally to lead and to miflead, as well as 
many others, pronounced that the hidory of Archimedes’s 
mirror was but a fable ; yet the power of fuch mirrors is 
now well edabliffied. Examples of fuch high authority 
fhould make us circumfpc-Ct. 
To conclude our remarks on the fubjeff of the mecha¬ 
nical arts, we drall obferve, that the l'uperiority of one 
manufacture over another mud depend chiefly upon the 
goodnefs of the material, joined w ith difpatch and perfeCt: 
workmanfiiip. The quality of the materials may com¬ 
monly be judged of by infpeCtion ; the quicknefs and 
perfection of the work depend upon the number of work¬ 
men collected together. When the workmen are nume¬ 
rous, each operation employs a different hand. One work¬ 
man will perform but one particular branch of the manu¬ 
facture 
