HOROLOGY. 
342 
and tinder mafles of iron may be called, for the fake of 
perfpicuity, is about thirteen inches ; that fize being 
nearly as large as clock-dials are ever made or wanted. 
The convexity of the hammer is exactly fitted to the con¬ 
cavity of the anvil, and may be defcribed, perhaps, as 
forming a portion of a circle fifty feet in diameter ; and 
the centres of both are kept true to each other, and con- 
lequently to the regularity of curve, by means of large 
fcrews and nuts, which adjult the pofition of the hammer 
by altering the perpendicularity of the bars of iron that 
the grooves aft upon. The power of this machine laves 
much labour in planilhing, as well as time; yet as it is 
infufficient wholly to prepare the coppers, and as the charge 
of erefting one would be very considerable, it w r ill never, 
perhaps, come into general ufe. 
In planilhing with this machine, it is neceffary to be 
provided with various thin circular pieces of lead, evenly 
flatted, and adapted in fize to the diameters of the cop¬ 
pers to be plani(lied. Without thefe the ftroke given by 
the hammer would have a very imperfeft effect ; and the 
impulfe given by the weight of its fall would alio be con¬ 
tinually weakening the foundation and bed of the anvil. 
The coppers prepared for planilhing by this machine are 
taken leparately, (the eyes having been previoufly cut 
out to a proper fize by means of an iron punch, a ham¬ 
mer, and a lead block,) and each one is laid upon a lead 
of a correfpondent diameter, and placed upon the anvil 
in fuch a manner that all the centres agree. The ham¬ 
mer, which has been hitherto retained at lbme height by an 
iron Hay fixed in one of the timbers, and moving on a 
pivot, is then let fall three or four times in quick fuccef- 
fion, it being each time lifted up, to the height of three 
feet or more, by means of the lever. The hammer is then 
again fallened by the flay, wliilft the copper is turned over 
on the lead, after which the operation is repeated ; and the 
copper is then taken oil', and another laid down, till the 
whole are gone through. The weight of the hammer, 
and the impetus acquired by its defeent, remove mof'c of 
the unevennefles in the coppers, yet cannot entirely re¬ 
medy them; aftrong and unequal lpring will Hill be felt, 
and, the metal being now rendered hard by the action of 
the hammer, annealing mull again be reforted to, and the 
coppers mult be pickled and cleaned as before. The ma¬ 
chine is then ufed a fecond time in a fimilar way; and af¬ 
terwards a third, a fourth, a fifth, and even a fixth and 
feventh, time, according to the diameters of the. coppers, 
or to the refraftorinefs* of the metals, due care being 
taken properly to anneal and pickle them between every 
operation. 
The coppers will tow be found of a regular lhape, and 
the fpring in the metal tolerably uniform; it is effential, 
however, to the perfection of the plate, that the fpring 
fhould be entirely uniform from edge to centre, otherwile 
the plate would warp and cockle in the fire. A Uind of 
intermediate procefs mult therefore be carried on between 
the taking the coppers from the machine, and before re¬ 
peating the annealings. This is performed by means of a 
circular brafs die, about a quarter of an inch in thicknefs, 
and from fifteen to eighteen inches in diameter, ferewed 
firmly down to a ftrong oaken block, having three ftout 
legs, placed triangular-wife, and of a fufficient height to 
ule conveniently when the artift is in a .Handing pollute. 
The die fiiould have the feme degree of curve as the ma¬ 
chine, otherwife the efteft produced by each would occa¬ 
sion a fort of reciprocal counteraftion. The coppers, 
having palled through the machine, are placed in fuccef- 
fion upon the die, and a wooden box-hammer (fome what 
refembling that ufed by gold-beaters) with two faces, the 
one a circle about three inches over, the other cut away 
on the front edges lb as to leave only a portion about an 
inch or an inch and a quarter in breadth remaining in 
the middle, is then taken, and the copper is both rubbed 
and (truck with it till the metal becomes too hard for any 
further impreflion to be made,, and requires- annealing. 
The circular end is ufed to ftrike the copper with, which 
is done by fiiort, quick beats of the hammer, the artift 
working from centre to edge, and communicating the 
neceffary motion and direftion to the coppers by means 
of the fingers of one hand, fo extended over the work as 
to give the requifite command in guiding it; the other 
end is employed in rubbing the coppers ftrongiy with a 
backward and forward aftion, under which they are 
moved upon the die by the fingers as before. Where the 
machine is not ufed, the planilhing mull then be entirely- 
performed in the way juft defcribed, and great care mull; 
be taken, that in the rubbing, the coppers be not bent, 
which would occafion both additional labour, and further 
annealing. No pofitive direftion can be given as to the 
number of times that the coppers mull be annealed in the 
courfe of the planilhing ; as a general rule, it may be 
faid that the larger the fize, the more frequently mult the 
annealings be repeated. For plates of from three to four 
inches, twice or thrice is commonly enough; from five 
to eight inches, about four or five times are requifite; for 
larger fizes, the annealings mull be continued till the 
fpring or aftion in the metal becomes uniform, as already 
mentioned. This is bell determined by the regularity 
with which the copper will flap or jerk ip to the curve 
given by planilhing when turned either fide uppermoft 
upon the die. When the planilhing is completed, the 
coppers are cut exaftly to the fizes required; and, having 
been pickled and cleaned, they’ are then ready to be ena¬ 
melled on. After the lall annealing, it is beft to planilh 
but (lightly, that the coppers may be left in a Hate 
comparative foftnels. 
For time-pieces, table-clocks, and fome others, round 
plates are commonly ufed, and in thefe cafes it is necef¬ 
fary to have moveable brafs dies formed into the curves 
required. Round plates are thole which have a confider¬ 
able rile in the centre, made by a pretty quick forcing-up 
of the copper into a fort of flioulder about where the cir¬ 
cles of the hours come, and afterwards continuing the 
rile more gradually. The bent fpatula and the fcratch- 
bnidi are chiefly employed to fet the coppers into thefe 
curves, and, where the rife is very quick from the edge, 
the copper is fometimes turned up as in fmall dials, that 
the enamel may be the better retained in its place. 
Thus much of the principles of the mechanifm of clocks. 
- What we have advanced, relative to the action of wheels 
and pinions upon the pendulum, will fuffice to convey an 
idea to any one, who has not previoufly- confidered the 
fubjeft, how admirably well adapted for the purpofes of a 
clock-movement this .property in mechanics is, by which 
an increafe of velocity is always accompanied by a pro^ 
portionate abatement of force; for by means of it, the 
maintaining power, however la; J ge, may be fo economi¬ 
cally .portioned out in minute quantities, fufficient only to 
compenlate the lofs of motion which the pendulum or ba¬ 
lance fuftains at each vibration, that it may be made to 
laft for many days, or even weeks, before it is exhaufted- 
by the great number of fucceffive minute deduftions which 
are made at periodical intervals ; at the lame time, certain 
wheels and pinions, by their numbers and due arrange¬ 
ment, divide and fubdivide, by means of hands and di¬ 
vided circles, the fexagefimal portions of each hour, de¬ 
nominated minutes, and alfo of each-minute by the name 
of leconds. The various offices of conmunicating motion, 
of increafing its velocity as at firft produced, of diminilh- 
ing the original force of the maintaining power, of divi¬ 
ding, fubdividing, counting, and indicating, the hours, 
minutes, and leconds, all performed by the Ample con¬ 
trivance of a clock-movement, or watch-movement, in 
conjunftion with the regulator, we hefitate not to affirm; 
when duly confidered, exhibit one of the molt linking 
inltanccs of human ingenuity. The experiments of the 
pbiiofopher, the calculations of the mathematician, and 
the perl'evering (kill of the mechanic, have combined to . 
produce ultimately this admirable piece of. mechanifm, of 
whi.ch 
