HOROLOGY. 
more, and by introducing two fuch wheels and pinions, 
it may be made to go a year at one winding up, with a 
maintaining power proportionably great. ' v 
It now remains to fpeak of that part of the movement 
which ftrikes the hour, See. The wheels compofing this 
part are correctly exhibited in-the preceding Engraving, 
viz. The great or firft wheel H, fig. 58, which is moved 
by the weight or fpring at the barrel G, in fixteen or 
thirty hour clocks; this has ufually pins, and is called the 
pin-wheel ; in eight-day pieces, the fecond wheel, I, is 
commonly the pin-wheel, or ftriking-wheel, which is 
moved by the former. Next to the ftriking-wheel is the 
detent-wheel, or hoop-wheel, K, having a hoop almoft 
round it, wherein is a vacancy at which the clock locks. 
The next is the third or fourth wheel, according to its 
diftance from the firft, called the warning-wheel, L. The 
laft is the flying pinion Q, with a fly or fan, to gather 
air, and fo bridle the rapacity of the clock’s motion. To 
thele mult be added the pinion of report; which drives 
round the locking-wheel, called alfo the count-wheel ; ordi¬ 
narily with' eleven notches in it, unequally diftant, to 
make the clock ftrike the hours. Befides the wheels, to 
the clock part belongs the rafli or ratch ; a kind of wheel 
with twelve large fangs, running concentrical to the 
dial-wheel, and Ierving to lift up the detents every hour, 
and make the clock ftrike ; the detents or flops, which, 
being lifted up and let- fall, lock and'unlock the clock in 
ftriking; the hammer, as S, which ftrikes the bell R; the 
hammer-tails, as T, by which the ftriking-pins draw back 
the hammers; latches, whereby the work is lifted up and 
unlocked; and lifting-pieces, as P, which lift up and un¬ 
lock the detents. 
That part of the movement which is defigned to mea- 
fure and exhibit the time on the dial-plate is called the 
watch-part of either clock or watch, becaufe much of the 
mechanifm is common to both. This will give us an 
opportunity of fho'wing the principal wheels of the clock 
in a different pofition from what they appear in fig. 56. 
Fig. 58, which fhows the ftriking-part, exhibits the watch 
or dial work alfo. Firft you will notice the pendulum ; 
whole parts are, the verge x, the pallets 5, 5, the rod yyy , 
the fork z, the flat 2, the bob or great ball 3, and the 
corrector or regulator 4, being a contrivance of Dr. Der- 
ham for bringing the pendulum to its nice vibration Sv 
2. The wheels, which are the crowned w heel F, in pocket- 
pieces, and living-wheel in pendulums ; Ierving to drive 
the balance or pendulum. 3. The contrate wheel E, which 
is that next the crown-wheel, &c. and w'hofe teeth and 
hoop lie contrary to thofe of other wheels; whence the 
name. 4. The great or firft wheel C, which is that the fu- 
fee B, See. immediately drives, by means of the chain or 
firing of the fpring-box or barrel A ; after which are the 
fecond wheel D, third wheel, See. Laftly, between the 
frame and dial-plate, is the pinion of report, which is 
that fixed on the arbor of the great wheel ; and ferves to 
drive the dial-wheel, as that ferves to carry the hand. 
For the illuftration of this part of the work which lies 
concealed, let ABC, fig. 59, reprefent the uppermoft fide 
of the frame-plate, as it appears when detached from the 
dial-plate ; the middle of this plate is perforated with a 
hole, receiving that end of the arbor of the centre-wdieel 
which carries the minute-hand ; near the plate is fixed 
the pinion of report a b of 10 teeth ; this drives a wheel cd 
of 40 teeth ; this wheel carries a pinion ef of 12 teeth; and 
this again drives a wheel gh with 36 teeth. 
As in the body of the clock the wheels every where 
drive the pinions ; here, on the contrary, the pinions 
drive the wheels, and by that means diminilh the motion, 
which is here neceffary; for rite hour-hand, which is ear¬ 
ned on a focket fixed on the wheel gh, is required to 
move but once round while the pinion ab moves 12 
times round. For this purpofe the motion of the wheel 
cd is -£ -of the pinion ab. Again, while the wheel cd, or 
the pinion ef, goes once round, it turns the wheel gh but 
-‘-part round ; confequently the motion of gh is but ^ of 
Vol. X. No. 664., 
329 
\ of the motion of ab-, now A of ^ is i. e. the hour- 
wheel gh moves once round in the time that the pinion 
of report, on the arbor of the centre or minute-wheel, 
makes 12 revolutions, as required. Hence the ftrufture 
of that part of a clock or watch which (hows the time 
may be eafily underftood. The cylinder A, fig. 58, put 
into motion by a weight or inclofed fpring, moves the 
fulee B, and the great wheel C, to which it is fixed by 
the line or cord that goes round each, and anfwers to the 
chain of a watch. 
The method of calculation is eafily underftood: for, 
fuppofe the great wheel C goes round once in 12 hour's, 
then if it be a royal pendulum clock, fwinging feconds, 
we have 60 X 6 ° x 12 —43200 feconds or beats in one 
turn of the great wheel. But becaufe there are fixty 
fwings or feconds in one minute, and the feconds are 
fliown by an index on the end of the arbor of the fwing- 
wheel, which in thofe clocks is*in an horizontal pofition; 
therefore, it is neceffary that the fwing-wheel F (liould 
have thirty teeth; whence 4 |-g- 00 — 720, the number to 
be broken into quotients for finding the number of teeth 
for the other wheels and pinions. 
In fpring-clocks, the difpofition of the wheels in the 
watch-part is fuch as is reprefented in the figure, where 
the crown-wheel F is in an horizontal pofition; the fe¬ 
conds not being (hown there by an index, as is done in 
the large pendulum-clocks. Whence in thefe clocks the 
wheels are difpofed in a different manner; C is the great 
wheel, and D the centre or minute-wheel, as before; but 
the contrate-wheel E is placed on one fide, and F the 
fwing-wheel is placed with its centre in the fame perpen¬ 
dicular line ID with the minute-wheel, and with its 
plane perpendicular to the horizon, as are all the others. 
Thus the minute and hour hands turn on the end of the 
arbor of the minute-wheel at a, and the fecond hand on 
the arbor of the fwing-wheel. 
The ftriking-part of a clock is fubjeft to great variety 
in the conftruftion, according to the genius of different 
artifts. In the year 1803 the Society for the Encourage¬ 
ment of Arts, See. prefented to Mr. John Prior, of Nefs- 
field, Yorklhire, a reward of thirty guineas, on account 
of his contrivance for the ftriking part of an eight-day 
clock. It confifts of a wheel and fly, with fix turns of a 
fpiral line, cut upon the wheel for the purpofe of count¬ 
ing the hours. The pins below this fpiral elevate the 
hammer, and thofe above are for the ufe of the detent. 
This (ingle wheel ferves the purpofe of count-wheel, pin- 
wheel, detent-wheel, and fly-wheel, and has fix revo¬ 
lutions in ftriking the 12 hours. If we fuppofe a train of 
wheels and pinions ufed in other ftriking parts to be made 
without error, and that the wheels and pinions would 
turn each other without (hake or play; then allowing the 
above fuppolition to be true, (though every mechanic 
knows it is not,) Mr. Prior’s ftriking-part would be 
found fix times fuperior to others, in ftriking the hottrs 
1, 2, 5, 7, 10, 1 x; twelve times fuperior in ftriking 4, 6, 8 ; 
and eighteen times, in ftriking 3, 9, and 12. In ftriking 
2, the inventor purpofely made an imperfection equal to 
the fpace of three teeth of the wheel; and, in ftriking 3,. 
an imperfeftion of nine or ten teeth ; and yet both thefe 
hours a,re (truck perfectly correft. The flies in clocks 
turn round, at a mean, about fixty times for every knock 
of the hammer, but this turns round only three times for 
the lame purpofe ; and, fuppofe the pivots were of equal 
diameters, the influence of oil on them would be as the 
number of revolutions in each. 
This invention is exhibited in the Engraving at fig. 60 
and 61. A, fig. 60, (hows the large wheel, on the face 
of which are funk or cut the (lx turns of a fpiral. B, the 
Angle worm lerew, which afts on the above wheel, and 
moves the fly C. D, the fpiral work of the wheel A. 
The black fpots (how the grooves into which the detents 
drop on ftriking the hour. E, the groove into which the 
locking-piece F drops when it ‘ftrikes one, and from 
which place it proceeds to the outward parts of the fpiral 
4 ,P in 
