CLOCK. 
movements may be seen ; as they are de- 
signed for ornament as well as use very 
elegant and expensive decorations are fre- 
qxiently added to them. 
The invention of moving time-pieces by 
springs first gave rise to portable time- 
pieces, or watches, for which see the articles 
Chronometer and Horology. 
Spring-clocks are sometimes called port- 
able clocks, but improperly, for no pendu- 
lum clocks can be made so as to be port- 
able : for this purpose the balance wheel 
and its spring must be substituted for the 
pendulum, and it is this point that makes 
the grand distinction between clocks and 
watches, of chronometers ; the properties of 
the balance spring, as a regulating povyer,wiil 
be found in the articles before mentioned. 
Clocks for astronomical purposes, in 
which extraordinary nicety in tire exact 
measurement of time is necessary, have (be- 
sides the compensation pendulums, detach- 
ed escapements with jewelled pallets, and 
other improvements before mentioned), a 
contrivance added to continue their move- 
ment, while the weight is winding up, which 
was first used in spring-moved chrono- 
meters. For this purpose a second lar ger 
ratchet wheel is added on the same arbor 
with that which admits the clock to be 
wound up, but with teeth pointing the con- 
trary way; a strong spring, usually the 
greatest portion of a circle, connects tliis 
large ratchet wheel with the great wheel of 
the clock, which is on the same axis with it ; 
one end of this spring being attached to the 
great wheel, and the other end to the large 
ratchet; and a catch proceeds from the 
inner face of the back plate to the teeth of 
this ratchet, which prevents its moving back 
when the clock is winding up, and serves as 
a support for the reaction of the maintain- 
ing spring. When the clock is left to the 
operation of the weight, the small ratchet 
turns round the large one and contracts, or 
coils up the spring till it has strength suffi. 
cient to impel the great wheel and train ; 
and when the action of the weight is sus- 
pended, as in winding up, the spring, freed 
from ‘the contracting power of the weight, 
expands itself and forces round the great 
wheel ; its action in the contrary direction 
on the great ratchet being prevented by the 
catch before mentioned. Le Roy is gene- 
rally supposed to have invented this im- 
provement for his chronometers ; but as he 
has proved that the fusee is unnecessary when 
a detached escapement is used, the same 
purpose might be answered in a much sim- 
pler manner, in those time-pieces which 
are moved by springs, by turning round the 
arbor to which the internal end of the main- 
spring is attached, in order to wind it up, 
instead of tiuning round the spring-box m 
the customary manner. 
Though Le Roy was the first who con- 
trived the spring impeller to prevent loss 
of time in winding up, Huygens was in 
reality the person with whom the idea 
originated ; for he contrived a method by 
which the weight of his clock should con- 
tinue to act on the train while it was draw- 
ing up ; the weight in his clock having been 
made to draw up in a similar manner to 
that used in the common wooden clocks, 
instead of being wound up as in our metallic 
clocks. Patoureaux’s clock has this contii- 
vance. . , 
Tlie following description of an eignt- 
day clock, with reference to the plate, will, 
it is hoped, sufficiently shew its construc- 
tion; and tlie plate will, it is presumed, 
assist in elucidating the various parts of 
clocks, and improvements before described. 
Plate Clock-work, is a representation of 
an ordinary eight-day clock, with repeat- 
ing, striking mechanism, 
Fig. 1, Clock-work, is an elevation of 
the clock sideways, shewing the pendulum 
and going part ; the striking movements are 
omitted in this figure, to avoid ponfusion ; 
fig, 2, is a projection of the wheel-work of 
both going and striking part : and fig. 3, is 
the dial-work, or mechanism immediately 
under the dial, (which is removed), and is 
that part which puts the striking train in 
motion eveiy hour, A clock of this kind 
contains two independent trains of wheel- 
work, each with its separate first mover ; 
one is constantly going, to indicate the time 
by the hands on the dial-plate ; the other 
is put in motion every hour, and strikes a 
bell, to tell the hour at a distance, a, fi- 
gures 1 and 2, is the barrel of the going 
part; it has a catgut band b wound round 
it, suspending the weight which keeps the 
clock going ; 96 is a wheel, (called the first 
or great wheel), of that number of teeth, 
upon the end of the barrel, turning a pinion 
of eight leaves on an arbor which carries 
the minute-hand. 64 is a wheel of 64 teeth 
on the same arbor, (called the centre 
wheel), turning the wheel 60 by a pinion 
of eight leaves on its arbor; this last wheel 
gives motion to the pinion of eight, on the 
arbor of the swing wheel 30, of 30 teeth ; 
d, h, are the pallets of the escapement fixed 
on an arbor c, fig. 1, going through the 
