CLOCK. 



portable clocks, but improperly, for no 

 pendulum clocks can be made so as to be 

 portable : 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, or chronometers : 

 the properties of the balance spring, as a 

 regulating power, will be found in the ar- 

 ticles before mentioned. 



Clocks for astronomical purposes, in 

 which extraordinary nicety in the exact 

 measurement of time is necessary, have 

 (besides the compensation pendulums, 

 detached escapements with jewelled pal- 

 lets, and other improvements before 

 mentioned) a contrivance added to con- 

 tinue their movement, while the weight 

 is winding up, which was first used in 

 spring-moved chronometers. For this 

 purpose, a second large -r ratchet wheel 

 is added on the same arbor with that 

 which admits the clock to be wound up, 

 but with teeth pointing the contrary 

 way ; a strong spring, usually the great- 

 est portion of a circle, connects this 

 large ratchet vi heel 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 the ratchet, 

 which prevents its mqving 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 

 sufficient to impel the great wheel and 

 train ; amd when the action of the weight 

 is suspended, 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 generally sup- 

 posed to have invented this improvement 

 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 simpler manner, in those time- 

 pieces which are moved by springs, by 

 turning round the arbor to which the in- 

 ternal end of the main-spring is attached, 

 in order to wind it up, instead of turning 

 round the spring-box in 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 

 continue to act on the train while it was 

 drawing up, the weight in his clock hav- 

 ing 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. Patou- 

 reaux's clock has this contrivance. 



The following description of an eight 

 day clock, with reference to the plate, 

 will, it is hoped, sufficiently shew its 

 construction; and the plate will, it is 

 presumed, assist in elucidating the va- 

 rious parts of clocks, and improvements, 

 before described. 



Plate Clock-work, is a representation 

 of an ordinary eight day clock, with re- 

 peating, striking mechanism. 



Fig. 1, Clock-work, is an elevation of 

 the clock, sideways, shewing the pendu- 

 lum and going part ; the striking move- 

 ments are omitted in this figure, to avoid 

 confusion ; fig. 2, is a projection of the 

 wheel-work of both going and striking 

 part ; and fig. 3, is the dial-work, or me- 

 chanism immediately under the dial, 

 (which is removed,) and is that part 

 which puts the striking train in motion 

 every hour. A clock of this kind con- 

 tains 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 dis- 

 tance, a. figures 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 mi- 

 nute hand. 64 is a wheel of 64 teeth on 

 the same arbor, (called the center 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 ar- 

 bor of the swing wheel 30, of 30 teeth ; 

 d, h, are the pallets of the escapement 

 fixed on an arbor e, fig. 1, going through 

 the back plate of the clock's frame, and 

 carrying a long lever /; this lever has a 

 small pin projecting from its lower end, 

 going into an oblong hole, made in the 

 rod B of the pendulum. The pendulum 

 consists of an inflexible metallic rod, sus- 

 pended by a very slender piece of steel- 

 spring, D, from a brass bar E, screwed 

 to the frame of the clock, haying a 



