of Magneto-Electricity. 



353 



On the Heat evolved by a Bar of Iron rotating under Magnetic 



Influence. 



Having removed the small electro-magnet from out of the 

 tube of the revolving piece, I fixed in its stead, in the centre 

 of the tube, a solid cylinder of iron 8 inches long and £ of an 

 inch in diameter. The tube was then, as before, filled with 

 water and rotated for a quarter of an hour between the poles 

 of the large electro-magnet. In the first experiments the 

 electro-magnet was excited by ten cells in a series of five 

 double pairs, a galvanometer being included in the circuit in 

 order to indicate the electric force applied. It was of course 

 placed, as before, so as not to be affected by the powerful 

 attraction of the electro-magnet. The precaution of interpo- 

 lating the experiments was adopted as usual. 



No, 13. 



Everything else remaining the same, I now used a battery 

 of six cells arranged in a series of three double pairs to excite 

 the electro-magnet. 



Phil. Mag. S. 3. Vol. 23. No. 153. Nov. 184-3. 2 A 



