H ORO 
the dope, but not upon it, nor'yet on the angular poiht 
of interfeffion. Indeed it is extremely difficult to give 
complete verbal directions for this delicate adjuftment, 
which requires long and attentive practice to do perfectly ; 
for frequently, after the pallets are hardened, which they 
mull be as much as poffibie, the lhape of the anchor is 
found to be altered, and the adjuftment of the pallets 
confequently deranged; to remedy this confequence, it is 
ufual to harden only the pallet-parts of the anchor, fo that, 
by certain ft rakes given near its arbor, the pallets may be 
brought in or fet out a little to reftify them ; but after 
fuch refliiication it will always be neceffary to try, in the 
turning-frame, or at leaft by a pair of bullet-compaffes, 
if the circular parts are again perfectly concentric, with¬ 
out which condition the pallets will not be truly what are 
called, dead-beat. 
Hitherto we have confidered the back pivot-hole of the 
pallets-arbor as being in the plate of the frame; but it 
becomes neceffary to cut away that portion of the back 
plate where the pivot-hole falls, by reafon of the crutch, 
or little rod of fteel, which muft be fcrewed to a collet 
attached behind the frame to the arbor, to form an L; 
which contrivance impreffes the force that the pallets re¬ 
ceive from the maintaining power upon the pendulum ; 
the bent end of the crutch is ufually inferted into a flit 
made in the verge or rod of the pendulum, but, when the 
bent part is divided and enclofes the pendulum-rod, it is 
denominated the fork ; the crutch is molt ufually about 
one fixth part of the whole length of the pendulum-rod, 
but there feems to be no fixed rule laid down by which 
its befit length might and ought to be determined in dif¬ 
ferent cafes, which therefore we think deferves further 
confideration. 
But to return to the pivot-hole of the pallet’s arbor; 
this, for the reafon we have juft given, is finally placed in 
a cock at the back of the pofterior plate, which is gene¬ 
rally lb fliaped as to furnifh alfo a point of fufpenfion for 
the pendulum. The exaft placing of the cock, fo that 
the arbor pivoted into it fhall be perfectly at right angles 
to the furface of the plates, is of the greateft importance, 
and therefore it ought to be placed and its fteady pins 
fixed, before the original pivot-hole, through which it 
muft protrude, is cut away in the plate, for in that cafe 
the protruding end of the arbor, while in its proper pou- 
tion after the adjuftment of the fcapement, will be like 
a fixed arbor on which to Hide the cock, and fix its pofi- 
tion before the fteady pins are applied and the fcrews 
fitted to their places. It is, however, the practice of fiome 
workmen to adjuft the fcapement, by moving the cock 
before the fteady pins are inferted. 
We might have noticed, that, after the anchor of the 
pallefs is fcrewed to thb collet of its arbor, it fhould be 
lufpended by the pivots of the verge, which is the name 
given to this arbor, to try if the weight of each pallet ex¬ 
actly balance that of the other, which may be effected by 
diminilhing the thicknefs of the heavier pallet a little by a 
fine file before it is finally polifhed; alfo before the crutch 
is fcrewed it fhould be hung on the verge of the pallets- 
arbor, after the pallets are balanced and fuffered to find 
their place of quiefcence, in order to find its own perpen¬ 
dicular direction, and then it fhould be fixed in that fitu- 
ation; for without this care it will require to be bent fo 
as to offend the eye, for the purpofe of putting the clock 
into beat, or otherwife will require a flit in it acrofs the 
centre, to admit of an eccentric adjuftment, or fome luch 
contrivance. When all the adjuftments of the fcapement 
are thus made, the pallet-faces,'if not jewelled, and alfo 
the pivots, muft be hardened, and finally drelfed by the 
ufual iucceffive operations of polifhing. 
The precautions we have hitherto dictated, in our di¬ 
rections for the fucceftive operations in clock-making, 
have for their principal objeft the regular tranfmifilon of 
a certain quantity of the maintaining power to the pen¬ 
dulum, in order to prelerve the arc of vibration unaltered, 
which is one of the two eil'ential qualities of the going- 
Vol.X. No. 665. 
LOGY. .141 
pendulum, on which the exaft meafufement of time de¬ 
pends ; the other, which is an indifpenfable quality of the 
pendulum, where great exaftnefs is required, is that by 
which its length is'preferved unaltered in all the varia¬ 
tions of temperature, as the centre of ofcillation regards 
the centre of fufpenfion. Thefe two properties of the 
pendulum, its conftant arc and eonftant length, confti- 
tute the excellence to which all the other parts of the 
mechaniffn are fubfervient, and without which no clock 
will continue invariably to indicate true time at all feafons 
of the year, however exquifite the workman (hip of the 
movement and other parts. In an ordinary clock, the 
iron oi- fteel rod of the pendulum is liable fo confiderablc 
alternate expanfions and contractions, which render acom- 
penfoting contrivance neceffary for pieces deftined for as¬ 
tronomical purpofes; and the various intentions to accom- 
plifh this end have been already noticed at p. 309-3n. 
As we have dwelt fo long on the mechanifm of the go¬ 
ing-part of a clock, which is the moll effential to be .at¬ 
tended to, we need not deferibe over again here, the offices 
of the different parts of the ftriking-meehanifm, which re¬ 
quires lels of fcience, and more of mere mechanical con¬ 
trivance, than the parts we have hitherto treated of. We 
fhall therefore conclude with a few words as to preparing 
the dial-plate for the enameller; which, though it may 
feem a work of little importance, requires no frnall care 
and fkill in the adjuftment. The copper, being procured 
from the flatting-mills in thin flips, and of an adequate 
diameter and thicknefs, is cut to nearly the required fize 
with a pair of ftrong feiffars, a circle having been firft 
ftruck with the compafies. If in a foft ftate, it is then, 
cleaned by the pickle, as it is called, which is either oil 
of vitriol or aquafortis mixed with water ; and, having 
been brufhed out with fand on a flat board, is wafhed and 
dried for planifhing; if otherwife, it muft be well annealed 
before it is thrown into the pickle, w here it muft lie till 
all the fcale is enough foftened to be removed by the 
hand-brufh, fand, and water. 
Planifhing is a very important part of this work; and 
too much care cannot be exerted in the procefs, as the 
neceffary regularity of furface almoft wholly depends upon 
it. In large plates the aftion of the fire has a very confi- 
dera’ole effect, as it caufes an expansion in the metal, 
which, unlefs properly guarded again ft, cannot but ope¬ 
rate to the imperfection, and perhaps total l’poiling, of the 
work.- In flatting alfo, a fort of twift is not unfrequehtly 
given to the copper, during its paffage through the rol¬ 
lers, that would afluredly caufe the plate to become une¬ 
ven and cut of ihape, were.it not to be removed by pla- 
nifhing and repeated annealings. Another effect produced 
by the fire, is occafioning the plate to rife, perhaps irre¬ 
gularly, towards the centre, and this can only be checked 
by counteracting the action which the heat would other- 
wife generate in the metal by good planifhing. To keep a 
large plate entirely flat is impoflibie; or at leaft no means 
have as yet been difeovered through which that ai w can 
be attained. The belt way, therefore, to provide againft 
the irregularities which the fire might caul'e, is to give to 
the copper, in the courle of planifhing, a'flight and even 
rife or curve from the edge to the centre; this can either 
be effected by the ufe of large brafs dies, or by a machine 
adapted for the purpofe. 
This machine, which is very little known in the trade, 
confifts of two principal parts; the one a folid rnafs of 
iron, with a concave and polifhed face, imbedded im- 
moveably in a ftrong oak block, firmly fixed on a foun¬ 
dation of brick-work, and the top edge hooped with a' 
thick iron ring, to prevent fplitting ; the other, an an- 
fwering and weighty mafs of iron with a convex face, 
fimilariy polifhed, and fixed in an upright frame of tim¬ 
ber, but fo contrived as to become moveable by means of 
Aiding grooves, a rope, a pulley, and a lever, and fo 
placed as to fall direftiy upon the mafs beneath, in a 
fimilar way to the nionkey of a pile-driving engine. The 
diameter both of the hammer and the anvil, as the upper 
4. S and 
