$fjf^ Proceedings of the Royal Society, 



termination of the law according to which the force diminishes as 

 the distance between the disc and magnets increases. It seems 

 to follow from these experiments, that when a thick copper plate 

 is made to revolve under a small magnet, the force tending to de- 

 viate the needle is directly as the velocity, and inversely as the 

 fourth power of the distance ; but that when magnets of considerr 

 able size are made to revolve under their copper discs, the dimi*? 

 nution follows more nearly the ratio of the inverse square of the 

 distance, or between the square and the cube, though not in any 

 constant ratio of an exact power. 



The author then investigated the law of force when copper discs 

 of different weights are set in rotation which, for small distances, 

 appear proportioned to the weights of the discs, but for smaller 

 ones appear to vary in some higher ratio. 



A paper On the Annual Variation of some of the Principal 



Fixed Stars, was communicated by John Pond, Esq., A.R., & F.R.S. 



This communication consisted principally of a table, stating 

 the annual variations of twenty-three of the principal fixed 

 stars, as -deduced from Dr. Brinkley's observations, and those of 

 the Astronomer Royal. On these, Mr. Pond remarks that out 

 of sixteen stars observed at Dublin, thirteen either indicate a 

 southern deviation, or at least are not inconsistent with it; 

 and that of these thirteen, about half indicate a greater deviation 

 than that assigned by Mr. Pond himself ; the other half a less ; 

 while the three remaining stars deviate northwards. 



Mr. Pond further remarked, that the examination of this table 

 is calculated rather to increase than to diminish scepticism on the 

 subject of the determination of such very small quantities, by 

 astronomical observation. He concluded by disclaiming all in- 

 tention of placing the subject in a controversial point of view, 

 and by expressing a hope that the difficulty will, in a very few 

 years, be satisfactorily cleared up, 



A Descnption of an Improved Hyfjrometer^ by Mr. 



Thomas Jones, was read to the Society. 



