254 



Prof. J. Henry's Contributions 



in the weight of the ash after fermentation, akhough I do not 

 imagine it would have been to the extent of fifteen to nine- 

 teen times the weight of the ash previous to it. 

 Duke Street, Liverpool, March 1840. 



XLVI. Contrihutio7is to Electr^icity and Magnetism. No. III. 

 . 071 Ele.ctro-magnetic Induction. By Joseph Henry, LL.D., 

 Prof, of Natural Philosophy i?i the College of New Jersey, 

 Princeton. 



[Continued from p. 210.] 



Section III. — On the Induction of Secondary Currents at a 



distance. 



45. T N the experiments given in the two preceding sections, 

 -3- the conductor which received the induction, was se- 

 parated from that which transmitted the primary current by 

 the tliickness only of a pane of glass ; but the action from this 

 arrangement was so energetic, that I was naturally led to try 

 the effect at a greater distance. 



46. For this purpose coil No. 1 was formed into a ring of 



Fig:. 4. 



<32 



a represents lielix No. 4, b coil No. 1, in the form of a ring, 



about two feet in diameter, and helix No. 4 placed as is shown 

 in the figure. When the helix was at the distance of about 

 sixteen inches from the middle of the plane of the ring, shocks 

 could be perceived through the tongue, and these rapidly in- 

 creased in intensity as the helix was lowered, and when it 

 reached the plane of the ring they were quite severe. The 

 effect, howevei', was still greater when the helix was moved 

 from ihe centre to the inner circumference, as at c : but when 

 it was placed without the ring, in contact with the outer cir- 



