LENZ ON ELECTRO-MAGNETISM. 



619 



periments as from those of Biot, that the action of a particle of the 

 electric currents which encircle the magnet upon every particle of 

 the spiral, is in the inverse ratio of the squares of the distance. 



It also immediately follows from the law just demonstrated that the 

 electric current produced in the various wire rings which inclose 

 tlie armature, by its removal from the magnet, is in the inverse ratio of 

 the diameter of the rings ; for the electromotive power is the same in 

 every ring, but the resistance it suffers in being conducted increases as 

 the diameter of the rings ; therefore the electric current, the quotient 

 of the electromotive power, by the resistance it suffers, decreases as the 

 diameter of the rings increases. 



III. Influence of the Thickness of the Wire of th£ Electromotive Spirals 

 on the Electromotive Power produced in them. 



I have also again made these experiments with the horseshoe mag- 

 net, since in this case the convolutions of the wires had always the same 

 magnitude. I here employed ten convolutions, which I formed from 

 the wires No. 1, No. 3, and No. 4, and in which the diagonals were in 

 the same proportion as the numbers 233 : 839 : 1661. The entire 

 length of the convolutions in each sort was 33 inches. The deviations 

 are contained in the following table. 



If we now combine the observations No. 1, at the beginning and end 

 of the series of experiments, and take their mean, we have the following 

 deviations : 



For No. 1 the deviation or a = 38-1, 

 _ No. 3 or a' = 39-6, 



— No. 4 



or a" = 39-7. 



From the proportion of the diagonals in which that of the wire of the 

 multiplier is expressed by 274, we find the following reduced lengths 

 (referred to the wire of the multiplier or No. 2) of our three spirals, 



