144 Current by the Rotation of a Magnet. 



edge of the disc farthest from the magnet, rub upon it while the 

 disc turns, and the rotary motion is caused by a treadle. When the 

 disc revolves about six times in a second, the needle of the multiplier 

 deviates from its natural position at an angle of about 30°. 



On joining the copper disk with another of iron of the same di- 

 ameter, no change was perceived in the deviation. The experiment 

 was repeated with a more powerful ndagnet, weighing twenty kilog. 

 (44.11 lbs.) and sustaining one hundred kilog. (220.5 lbs.) but the 

 tension of the electricity of the revolving disc was not increased. 

 The diameter of the first disc was eleven centimetres, (4.3 inches,) 

 that of the second seventeen centimetres, (6.7 inches.) 



It appears that copper acts under the influence of a magnet, as a 

 steel bar tempered and magnetized, under that of an electrical cur- 

 rent — it is known that the current, whatever may be the power of the 

 Voltaic battery, does not sensibly increase the force of a magnet of 

 tempered steel. 



Art. XIV. — M. Ampere's communication to the Academy of Sciences 

 upon an experiment of M. Pixii relative to a Current produced 

 by the Rotation of a Magnet with an improved apparatus, Oct. 

 29, 1832. Translated from the Annales de Chim. et de Phys., 

 Sept., 1832 ; by Oliver P. Hubbard, Assistant in the Chemical 

 Department in Yale College. 



M. Hachette has reported the experiments made with an appara- 

 tus constructed by M. Pixii, for producing an electrical current, by 

 making ahorse shoe magnet revolve, face to face, with a fixed horse shoe 

 of soft iron, the latter being wound with a silk-bound copper wire ; 

 after having obtained vivid sparks with an apparatus, in which the mag- 

 net supported thirty livres, (33 lbs.) and the wire around it made five 

 hundred turns, a magnet supporting more than one hundred kilog. 

 (220.5 lbs.) and wound with a wire of one thousand metres, (1093.6 

 yds.) was used and the following effects were produced. 1. Vivid 

 sparks : 2. Shocks of considerable force : 3. A numbness and invol- 

 untary movements of the fingers, when immersed in vessels of acidu- 

 lated water with which the ends of the wires communicated : 4. A 

 great divergence of the gold leaves in the condenser of Volta : 5. A 

 rapid decomposition of water, previously mixed with a little sulphuric 

 acid to increase its conducting power. 



In these different experiments the current took place in the con- 

 ducting wire in a different direction at each semi-revolution of the 



