CLOCK. 
lias struck, that it may not stop the sound. 
The eiglith pin in tlie wheel 64 must pass 
by the hammer tail 78 times in striking the 
12 hours, 
8 + 9 + 10 + 11 + 12 z= 78, and as its 
pinion has eight leaves, each leaf of the 
pinion answers to a pin in the wheel 64 ; 
now as the great wheel has 78 teeth, it 
will turn once in 12 hours, the same as the 
other great wheel 96. In the wheel 64 
eight of its teeth correspond to one of the 
pins for the hammer, and as the pinion of 
the wheel o has eight teeth, it (wheel o) 
will turn once for each stroke of the ham- 
mer. By the remaining wheels, one, o, mul- 
tiplying six, and the other, p, eight times, 
the fly will turn 6 X 8 =: 48 times for one 
turn ol’o = one sti'oke of the hammer. Fig. 
3 is also mechanism relating to the striking 
part ; r is a small pinion of one tooth, called 
the gathering pallet, on the arbor of wheel 
0 , and consequently turns once for each 
stroke of the hammer ; s is a segment of a 
large wheel which it turns, (called the rack) ; 
t is an arm attached to the rack, whose 
end rests against a spiral plate, V, called 
the snail ; this is fixed on the tubular arbor 
before described of the hour hand and 
wheel 72, and turns round with it once in 
12 hours. The plate is divided into 12 equal 
angles, 30 degrees each, and as it turns, 
each of these answers to an hour; the circu- 
lar arcs forming the circumference of the 
snail are struck from the centre of the 
arbor between each division with a diffe- 
rent radius, decreasing a certain quantity 
each time in the order of the hours. The 
circular part of the rack s is cut into teeth, 
each of which is of such a length, that 
every step upon the snail shall answer to 
one of them ; is a spring pressing against 
the tail of the rack, and acting to throw 
the arm of the rack against the snail ; g is 
a click called the hawk’s bill, taking into 
the teeth of the rack, and holding it up in 
opposition to the spring w, i A: is a three- 
armed detent, called the warning piece, 
the arm k is bent at its end, and passes 
through a hole in the front plate of the 
clock, so as to catch a pin placed in one 
of the arms of the wheel p, fig. 2, and which 
describes the dotted circle in fig. 3, the other 
arm i stands so as to fall in the way of a pin in 
the wheel 40. In the present position of the 
figure, the wlieels of the striking train are in 
motion, and would continue turning until the 
gathering pallet r, which turns once at each 
stroke of the hammer, by its tooth lifts the 
rack s in opposition to the spring u>, one 
tooth each turn, and the hawk’s bill g re- 
tains the rack, until a pin in the end of the 
rack is brought in the way of the lever of 
the gathering pallet r, and stops the wheels 
from turning any further : it is in this posi- 
tion with the rack wound up, till its pin 
arrests the tail r, that we shall begin to 
describe the operation of the striking of 
the clock. The wheel 40, as we have said 
before, turns once in an hour, and conse- 
quently at the expiration of every hour 
the pin in it takes the end i, and moves it 
towards the spring near it, this depresses the 
end k until it falls in the circle of the mo- 
tion of the pin in the wheel p, fig. 2, at the 
same time the short tail depresses one end 
of the hawk’s bill, and raises the other g, 
so as to clear the teeth of the rack s ; im- 
mediately the spring w throws the rack 
back, until the end of its tail t touches that 
part of the snail which is nearest it ; when 
the rack falls back, the pin in it is moved 
clear of the gathering pallet r, and the 
wheels set at liberty ; the maintaining pow- 
er puts them in motion ; but in a very short 
time before the hammer has struck, the 
pin in the wheel p falls against the end of 
k and stops the whole : this operation hap- 
pens a tew minutes before the clock strikes, 
and this noise of the wheels turning is 
called the warning ; when the hour is ex- 
pired, the wheel 40 has turned so far as to 
allow the end of i to slip over its pin, as in 
the figure ; the small spring pressing against 
it raises the end fc so as to be within the 
circle of the pin in the wheel p, fig. 2 : every 
obstacle is now removed, and the wheels 
run on the pinion ; the wheel 64 raises the 
hammer r, and it strikes on the bell, the 
gathering pallet r takes up the rack, a tooth 
at each turn, the hawk’s bill g retaining it 
until the pin in the rack comes under the 
gathering pallet r, and stops the motion of 
the whole machine, till the pin in the wheel 
40 at the next hour takes the warning piece 
i fc, and repeats the operation we have now 
described. As the gathering pallet turns 
once for each blow of the hammer, and its 
tooth gathers up one tooth of the rack at 
each turn, it is evident the number of teeth 
the rack is allowed to fall back limits the 
number of strokes the hammer will make, 
’rhis is done by the rack’s tail t resting on 
the snail ; each step of the snail answers to 
one tooth of the rack, and one stroke of the 
hammer ; at each hour a fresh step of the 
snail is turned to the tail of the rack, and 
