*578 



SCIENCE. 



Science, <}j a ] g an j hands. The two movements influence each 

 Curiosities Qlher physically, and their slight anomalies are reduced 



_'"' _. more than one half. The continued agreement of the 

 two chronometers is a security against any errors. 

 One of these instruments was submitted by the French 

 Board of Longitude to very severe tests, and even to 

 that of a vacuum ; but the two second hands never 

 ceased to beat together to the same fraction of a second. 

 M. Breguet has not explained how the two chrono- 

 meters influence each other physically ; but we have 

 no doubt that they do it by means of the balances, in 

 the same way that two clocks agree with one another, 

 by their pendulums getting into the same train of vi- 

 bration. Some curious observations on this subject 

 have already been made in our article HOROLOGY, 

 Vol. XI. p. 162. 



7. Breguet' s Sympathetic Clock, 



Breguet'* This curious piece of mechanism, the construction 



sympathetic o f which has not been published, has the property of 



.-Jock. setting to the proper time, and regulating a repeating 



watch made for the purpose. This repeater is carried 



in the pocket during the day, and at night it is placed 



above the pendulum in a sort of frame, which forms 



part of the decoration of the clock. 



If the repeater is put wrong so as to go too fast or 

 too slow even for a quarter of an hour, it is sufficient 

 to place it before noon or midnight in its watch frame, 

 'in order that at these two times we may see the hands 

 either move forward or backward to the time marked 

 by the clock. The interior regulation of the watch is 

 restored by the same means with as much accuracy as 

 it could be done by an artist after a trial of it for se- 

 veral days. 



8. On the Use of the Common Watch for Philosophical 

 purposes. 



. As a watch is often the only time-piece which can 

 be commanded for occasional philosophical purposes, 

 it becomes of some importance to have a method of 

 reckoning short portions of time by it with facility and 

 accuracy. The Rev, Mr. Pearson has shown that (what- 

 ever be the numbers of which the wheelwork consists, if 

 we divide double the product of the numbers of teeth 

 in all the wheels from the centre wheel to the crown 

 wheel exclusively, by the product of the hours of all 

 the pinions which engage in those wheels, the quotient 

 will express the number of beats of the watch in one 

 hour. If the quotient is divided by 3600, the number 

 of seconds in an hour, we shall then have the number 

 of beats in one second. 



In the above calculation, the wheels and pinions 

 which constitute the dial work are not taken into ac- 

 count, nor the great wheel and pinion with which 

 it acts, because the only use of the former is to 

 cause the hour and minute hands to revolve in their 

 proper time, and the use of the great wheel and pi- 

 nion is to determine in conjunction with the number 

 of spirals on the fusee the number of hours that the 

 watch will continue to go at one winding up of the 

 chain round the mainspring barrel. The reason why 

 double the product of the wheels is used, is that only 

 one tooth of the crown wheel completely escapes from 

 the palates at every two vibrations of the balance. 



Let us suppose the watch used to have the following 

 numbers. See HOBOLOGY, Plate CCCII. Fig. 1. and 

 Vol. XI. p. 125. 



Now 



OH the use 

 of the 

 common 

 watch for 



philosophi- 

 cal pur- 

 poses. 



Centre wheel M and pinion a, 

 Third wheel E and pinion b, 

 Contrate wheel K and pinion c, 

 Crown wheel C, . 



Palates p, p, . . . 



54X48X48X15X2 3732480 



54 6 

 43 6 

 486 

 15 

 2 



Seieicc, 

 Curiosities 



beats 



an hour, or 4.75 beats in a second. The number of 

 spirals on the fusee is 7, consequently the number of 

 hours that the watch will go at one winding up, will 



48 40 36 



be 7 X T = 28, and the dial-work being x = 



' J. At 1\J * 



1440 



= 12, shows that while the driving pinion of 10 



1 At\J 



goes twelve times round, the last wheel of 36 goes on- 

 ly once, and consequently that the angular velocities 

 of the two hands carried by their hollow axles are to 

 each other as 1 2 to 1 . 



Mr. Pearson has shown, that a watch with the 

 following numbers will indicate hours, minutes, and 

 seconds by three hands, and give four beats in a second. 



Great wheel, . ... 50 teeth. 

 Centre wheel M and pinion a, 6'0 10 

 Third wheel L and pinion (), 64 8 

 Contrate wheel K and pinion c, 48 8 

 Crown wheel C and pinion, 15 6 



Palates p, p, . . .2 



The dial-work as usual. The fusee has six spirals, 

 and the watch goes 30 hours. By the above rule, the 

 beats will be calculated thus : 



60x64x48x15 5529600 



,- = = 14400 beats in an hour, 



8x8x6 384 



and 



14400 



=4 the number of beats in a second. See 





Nicholson's Journal, 4to. vol. iii. p. 49- 



9. Description of some of the Clocks invented by M. 

 Serviere. 



In the cabinet of pieces of mechanism made by the Descriptioa 

 late M . Serviere, there were many clocks invented by of some of 

 himself, and exhibiting much ingenuity. The ac- 

 counts which have been published of these inventions , 

 do not enable us to describe their interior mechanism ; 

 but the ingenious artist who sees the effects which are 

 produced, and the external structure of the clocks, can 

 have no difficulty in making them. 



Most of these clocks, all of which were made by M. 

 Serviere himself, operate by the elasticity of springs, 

 the gravity of weights, and the motion of water or of 

 sand. 



One of these clocks is represented in Plate PLATE 

 CCCCLXXXV. Fig. 12. It consists of a dome sup- CCCCI.XXXT. 

 ported by six columns on a hexagonal base. Around Fig- 12. 

 these columns are coiled two .copper wires running 

 in a spiral, and parallel to each other, from the dome 

 to the pedestal. These copper wires are fixed to the 

 columns by small consols, so as to form a channel or 

 groove, which permits a polished copper ball to de- 

 scend by its own weight from the top of the railway 

 to the bottom. As soon as the copper ball reaches the 

 bottom it enters a hole H, where it falls upon a spring, 

 whose detent being loosened by the impulse, throws 

 it up again with the utmost nicety through the hole G 

 4 



