240 Intelligence and Miscellaneous Articles, 



return more or less completely to their transversal position, the induc- 

 tion-current thereby formed must have such a direction that it opposes 

 this motion, and must thus be in an opposite direction to the cur- 

 rent passed through the wire. — PoggendorfF s Annalen, Dec. 1866. 



APPLICATION OF THE TUNING-FORK TO HOROLOGY. 

 BY M. NIAUDET-BREGUET. 



M. Duhamel, and several physicists after him, have used the 

 iuning-fork for measuring small intervals of time. Following their 

 steps, I have proposed to myself to prolong indefinitely the vibra- 

 tions of a tuning-fork by clockwork. 



The apparatus I have constructed consists, like an ordinary clock, 

 of two parts, a clockwork and an apparatus for isochronous oscilla- 

 tions, acting on each other by the intervention of an escapement. 

 The tuning-fork regulates the rate of the clockwork, which in turn 

 gives at each vibration a small impulse to the tuning-fork, necessary 

 for prolonging its oscillatory motion. The clockwork, by means of 

 needles on the axes and turning in front of dials, renders it possible 

 to count the vibrations of the fork. 



The most accurate method of controlling the regularity of an in- 

 strument of this kind consists in comparing the regulating tuning- 

 fork with a free one, by M. Lissajous's optical methods. I have 

 thus been able to confirm the agreement of the two forks once set 

 going, the free tuning-fork being put in vibration by the hand each 

 time the comparison is to be renewed. The accord is retained even 

 if the motive-weight of the apparatus is doubled or tripled. 



The tuning-fork which I used made about 100 single vibrations 

 (50 double) in a second. I have tried another which made about 

 200 single vibrations in a second ; and the apparatus worked with- 

 out necessitating any change. I think it certain that much more 

 acute tuning-forks might be used, provided the dimensions of the 

 escapement were suitably diminished. 



It is easily understood that by placing on the limbs of the tuning- 

 fork two equal symmetrical masses, the rapidity of the vibrations 

 will be diminished ; and it is easy to conceive arrangements by 

 which all velocities between two extreme limits can be obtained. 



I think the principle of the instrument might be very useful in 

 chronoscopic experiments — that is to say, those destined to measure 

 small intervals of time. It might also be used for giving a uniform 

 motion to various apparatus of registration or observation which are 

 employed in the sciences. Lastly, it gives synchronism to two 

 rapid clockwork movements, which has not yet been realized, and 

 which is frequently wanted in telegraphic and other applications. — 

 Comptes Rendus, December 10, 1866. 



APR. 



