Drs. Stewart and Schuster on a Magnetized Copper Wire. 535 



May 7. — "William Spottiswoode, M.A., Treasurer and Vice-Presi- 

 dent, in the Chair. 



The following communication was read : — 



" Preliminary Experiments on a Magnetized Copper Wire." By 

 Professor Balfour Stewart, LL.D., E.R.S., and Arthur Schuster, 

 Ph.D. 



1. The following experiments were made in the Physical Labo- 

 ratory of Owens College, Manchester. The copper wire employed 

 (ABCD, see fig.) was found to contain no perceptible trace of 



iron, nor was it sensibly magnetic, behaving quite in a neutral 

 manner when tested by the highest magnetic power at our disposal. 

 It was covered with gutta percha. The diameter of the wire was 

 0*0487 inch. The wire was wound fifty-three times, in one direc- 

 tion, round the poles of a powerful electromagnet, the length of 

 wire encircling these poles being about twelve metres. The direct 

 distance of the magnet from the galvanometer, Gr, was about twelve 

 metres. 



A Wheatstone bridge was employed, and a very delicate Thom- 

 son's reflecting galvanometer by Elliott Brothers, of which the re- 

 sistance was 5540 B.-A. units. A circuit-breaker was placed in the 

 circuit at E, close to the bridge. On some occasions, we used one 

 consisting of a solid key, which might be removed, thus breaking 

 the circuit ; but, on other occasions, a fluid or mercurial circuit- 

 breaker was employed. 



When the left-hand pole of the electromagnet (see fig.) was made 

 north the arrangement was called (1), and when the other pole was 

 made north the arrangement was called (2). It will thus be seen. 



