Proceedings of the Royal Sociely, 277 



on the various metals, in the course of which M. Arago*s results 

 of the diminution of effect by division of the metallic plates used 

 were verified ; and the further curious fact ascertained, that re- 

 establishing the metallic contact with other metals restores the 

 force, either wholly or in great measure ; and that even when the 

 metal used for soldering has, in itself, but a very feeble magnetic 

 power, thus affording a power of magnifying weak degrees of mag- 

 netism. The law of diminution of the force by increase of distance 

 was next investigated. It appears to follow no constant progres- 

 sion according to a fixed power of the distance, but to vary be- 

 tween the square and the cube. 



The remainder of this paper was devoted to some able and ela- 

 borate reasoning on the facts detailed. — The authors conceive that 

 they may be all explained without any new hypothesis in mag- 

 netism, by supposing simply that time is requisite both for the 

 developement and loss of magnetism ; and that different metals 

 differ in respect, not only of the time they require, but in the 

 intensity of the force ultimately producible in them ; and they 

 apply this explanation not only to their own results, but to those 

 obtained by Mr. Barlow in his paper on the rotation of iron. 



A paper was read containing an account of Experiments 



on the Magnetism produced by Rotation^ by S. H, Christie, Esq., in 

 a letter to Mr. Herschell. 



Mr. Christie, in this communication, gave an account of some 

 experiments on the developement of magnetism in copper by rota- 

 tion. He corroborated by his own experience the results obtained 

 by Mr. Herschell, in which a disc of copper was set in rotation by 

 the rotation of one or more magnets beneath it, both in the 

 case where poles of the same name were immediately below 

 the disc, and when of a contrary name. The actions appeared 

 equally intense in both cases, and from this circumstance, he con- 

 cludes the magnetism thus communicated to the copper, to be 

 extremely transient. The experiment was varied by combining 

 the revolving magnets differently, and the results were stated. 



The next experiments of Mr. Christie were directed to the de- 



