H O R C 
will enable the workman to metamorphofe a portable clock 
into a large one, and the contrary, without difficulty, or 
without even a knowledge of the operations of arithmetic. 
We might have extended this Table to take in different 
intermediate lengths of the pendulum and correfponding 
number of vibrations per fecond ; but our objeft is to ba- 
niih incommenfurate vibrations from clock-movements, 
and to introduce thofe only which conftitute fome conve¬ 
nient fubdiviiion of the fecond, to anfwer the nicer pur- 
pofes of philofophy without extra labour and expence. 
The three or four laft horizontal columns indeed, it may 
be faid, will not be of much fervice in clock-movements, by 
reafon of the lhortnefs of the pendulums; but they will 
be found particularly ufeful in watch-work, as will alfo 
the other Tables, which are fo comprehenfive as to apply 
■with equal propriety to clock and watch movements ; fo 
that we fliall not have occafion to revert to this fubjeft 
again. 
We fliall not pretend to teach the manipulation of the 
arbors, pinions, and wheels, of a clock, but have merely 
fpoken of their diameters, numbers of teeth, See. It can¬ 
not be neceffary to enter into a detail of the manner of 
forging the arbors, or of calling the brafs by models of 
given dimenfionSj, the ironmongers and tool-fellers having 
on fale fets of wheels, and arbors with pinions of different 
numbers ready flit, and alfo pinion fteel-wire drawn into 
a proper fliape for the teeth of fmall pinions, of all which 
clock-makers ufually avail themfelves inftead of preparing 
them ; otherwife the.brafs-founders in Chancery-lane, and 
in other parts of London, as well as in Lancafliire, will 
call wheels to any model at a certain price per pound, 
which is a great convenience to the workman who has oc- 
calion for unufual flzes in his wheel-work. 
It will not, however, be deemed foreign to our purpofe 
to mention, that it is often found requifite to foften the 
pinions of Heel, and their arbors, before the graver for 
turning can cut them with fufficient eafe in the turning- 
frame; this foftening is ufually effected by putting the 
fteel pieces into a wood fire for fome hours, and leaving 
them to cool gradually as the lire goes out. The wheels 
are generally eroded in their original caff flate, to make 
them light, in order to avoid the effect of their inertia, 
and to prevent trillion on the pivots of the arbors; but 
it is neceffary to hammer the rims and other parts of a 
wheel well before they are Sled flat, to be put on the ar¬ 
bor for turning, otherwife the metal would be too foft to 
wear well, and the teeth of a wheel would not Hand the 
graver in the operation of being turned, after it is cut by 
the engine, in cafe the diameter fhould require to be re¬ 
duced, as is commonly done, to work well in its calliper 
with its pinion. When the wheels are hammered, and 
filed flat to nearly their exaft thicknels, according to the 
force they are deilined to tranfmit, they are turned in the 
turning-frame to their practical diameters, after being 
previoufly perforated in the centre, and l'crewed fall on a 
fuitable arbor. They are then in a flate to be cut by an 
engine made on purpofe, which is not always in the pof- 
feflion of fhe clock-maker, particularly in large towns, but 
which is ufually kept by fome individual, whofe bufinefs 
is chiefly to cut wheels for the clock-makers at a certain 
price per fet. An ingenious workman, of the name of 
Brown, who lived in King-flreet, Seven-dials, but who 
is now dead, was noted in London for his dexterity and 
accuracy in cutting clock-wheels, and occafionally pi¬ 
nions, into any number of teeth; his engine, however, is 
now in the hands- of Mr. Fidler, mathematical inftrument- 
maker, Oxford-market, London, who has lately begun 
to ufe it ; but the beft engine for this purpofe at prefent 
in conflant ufe, belongs to Mr. Edward Troughton, of 
Fleet-flreet, and is ufed by James Fayer, at No. 35, White- 
lion-flreet, Pentonville, London. This engine, which was 
contrived and made by the late ingenious mechanic Rehe, 
will round the teeth at the fame time that it cuts them, 
if required ; and is valued-at 300I. in its prefent.Hate. 
The clock-makers of the prefent day have greatly the 
LOGY. 
advantage of thofe who laboured in the art in the infancy 
of clock-making, in. that they have l'ome of the moll dif¬ 
ficult operations in theory, fuch as dividing and cutting 
the wheels, and forming the fpiral groove of the fufee, 
done by engines not only in lefs than one-hundredth part 
of the time, but with infinitely more accuracy, than they 
could be performed by hand with manual tools; and it 
is much to be defired that they would, like watch-makers*, 
have their wheels cut and rounded in the engine at the 
fame time. But it has been remarked, by a philofopher 
well qualified to make the remark, (Mr. W. Nicholfon,) 
that the introduction of new inftruments, and of new oper¬ 
ations, requires the fame fpace of time that is neceffary 
for inftrufting another generation ; fo much does that 
facility, which arifes out of habit, militate againft the 
adoption of new practices. We mufl, therefore, fuppofe 
our wheels returned from the engine with their teeth not 
rounded, and proceed with our detail. 
When a wheel has been cut, in the ordinary way, by 
the engine, there are ufually fome filaments of metal, de¬ 
nominated burs, left at the edges of the teeth by the 
cutter, as well as general roughnefs on the fides and at 
the bottom of the fpaces. Thefe are firfl cleared away by 
a fine file, juft thin enough to go into the fpace left by 
the cutter, which is called an equalling file, from its fup- 
pofed property of leaving all the fpaces equal, when the 
burs are removed. The crofl'es of the wheel and interior 
edges of the rim are next dreffed, firfl by a rough file, 
then by a fmooth one, and laftly by a burnifher of po'ifhed 
fteel. The arbor 3s next turned in a frame, by a well- 
tempered tool, or flrong graver, to its propofed thicknefs, 
and the pinion reduced to its practical diameter ; after 
which its teeth are rounded, hardened, and poliflied, each 
of which operations we will fuppofe to be underilood, 
and the wheel is riveted oil a fhoulder left on the proper 
end of the pinion, exterior or interior, as the work may 
require, if it is on the hour-arbor; otherwife it may be 
riveted, or Hill better fixed by two oppofite fcrevvs, on a 
brafs collet, which is previoufly foldered upon fucli part 
of the arbor, to which it belongs, as the place of the pi¬ 
nion which it actuates may require. The French call 
that portion of an arbor, which is between the wheel and 
the remote pivot, a -tige ; and that portion a tigeron, which 
lies between the wheel and the nearer pivot. Some of the 
moll fkilful workmen contend that the wheel ought al¬ 
ways to be placed on its arbor, fo as to be equally diftant 
from both pivots, and we have feen clocks conftrucled 
with cocks, at the back of the plates, to hold the pivots 
of projecting arbors, in order to e fie ft this purpofe; but 
we will not undertake to affirm that this additional work 
is compenlated by any advantage thus gained ; we rather 
conceive that the grievance complained of in the ordinary 
method of pivoting in the plates, viz. the alleged unequal, 
preffure and confequent unequal friction in the oppofite 
pivot-holes, when a pinion is at one end of the arbor, is 
to be attributed to another caufe principally; i. e. the too 
great aperture of the pivot-holes ; for workmen have a. 
maxim, that “ the pivots mufl have play to avoid friftion,” 
but they feenr not always to underfland what this play 
means; it certainly onghf not to mean, that the holes 
fhould be much larger than the pivots which are to turn 
in them, for in that cafe the pivots would be driven 
round the interior circumference of the holes, and caufe 
the wheel to aft at different depths in the pinion, whichs 
would be a great evil ; the''meaning of the maxim is, ;h..t 
the flioulders of the arbors fhould not prefs againft the 
plates when mounted, but that eacll arbor fhould have a 
little play in the direftion of its length, or, in other 
words, be left fo as to be at liberty to move a little back¬ 
wards and forwards; which condition feems requifite. 
Time and wear generally make them ealy. enough. 
We will now fuppofe all the wheels and pinions rounded 
neatly in the bay-leaf form, and them aftion tried in the 
deepening-tool, with the correfponding pivot-holes drilled 
with drifts refpeftively proportioned to the propofed thick- 
3 aef's 
