THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



[FOURTH SERIES.] 



MA Y 1863. 



XLIV. Account of some Experiments showing the Change of Rate 

 produced in a Clock by a particular case of Magnetic Action. 

 By William Ellis, Esq., of the Royal Observatory ,Greenwich*. 



HAVING made a series of experiments, the particular object 

 of which was to ascertain whether it would be possible 

 easily to change permanently the rate of a clock by the action of 

 magnets, and so avoid the necessity of touching its pendulum 

 screw, I have been requested by the Astronomer Royal to draw 

 up an account of these experiments, since the results appear to 

 possess some features which are in themselves likely to be inter- 

 esting generally, independently of the possible practical applica- 

 tion of the principle. The account is not, however, offered as 

 containing anything which adds in any important degree to fun- 

 damental laws already known, but chiefly because the experi- 

 ments so well illustrate the peculiar action of two magnets on 

 each other when brought very near together. 



The clock made use of for trial of the principle was one of the 

 spare clocks at the Royal Observatory — one whose pendulum, 

 vibrating seconds, consisted of a wooden rod fitted with a lenti- 

 cular-shaped bob of lead. Near the lower end of the pendulum- 

 rod there was fixed a permanent bar magnet, in a vertical posi- 

 tion. Above this, and supported by the clock-case, there was 

 fixed another magnet, entirely similar, also in a vertical posi- 

 tion, and so placed that, when the pendulum-rod was at rest, the 

 lower end of the fixed magnet was precisely over the upper end 

 of the pendulum-magnet. The broad part of the magnets was 

 towards the front. The clock-rate having been found with the 

 pendulum-magnet only in position, the fixed magnet was then 

 added, and the rate determined with this magnet placed at dif- 

 ferent distances above the pendulum-magnet. The clock was 

 rated with the poles of each magnet in reversed positions with 

 * Communicated by the Author. 



Phil. Mag. S. 4. Vol. 25. No. 169. May 1863. Z 



