-LENZ ON ELECTRO-MAGNETISM. 623 



of wires of different substances, but in every other respect placed in ex- 

 actly the same circumstances, is completely the same for all these sub- 

 stances "*. 



Hence again it immediately follows that in two perfectly equal wire 

 rings of ditterent substance, surrounding the magnetic armature, the 

 electric currents which are produced by taking the armature off or 

 placing it on the magnet, are in direct proportion as the capacities of 

 the substances for conducting electricity. Silver and copper wires 

 therefore are the most advantageous. 



From the latter observations we shall easily be able to deduce the 

 capacity of the four metals for conducting, if we make a second similar 

 observation, in which instead of bringing into the circle of the electric 

 current two spirals of different metals, we make use of two of the al- 

 ready used copper spirals, and then place either of them on the armature, 

 and determine the angle of deviation. Let this angle be called a; and, 

 for the other spirals, in the order in which they followed in the obser- 

 vation (therefore the copper spiral, with that of iron, platina, and brass), 

 let these angles be designated by a', a", and a'". Further, let the com- 

 bined lengths of the wire of the multiplier of the conducting wires and 

 that of the connecting wire of both spirals (all reduced to the diameter 

 of the wire of the multiplier) be called L ; but the lengths, which are 

 equal in all the spirals, reduced also to the same diameter, be X; 

 we will further designate by 1, m', m", m'", the conductive power of 

 the metals in the above order, where that of the copper is also expressed 

 byl. 



If we take the general formula (A.), namely 

 X = (L + / + X)p • sin. i a, 

 we must here, since the wires are no longer of the same kind, substitute 

 for the resistance (L + Z + X), the resistances f 



(L + .).(l + A), (L + i^,).a„d (l+^,), 



since they stand in inverse proportion to the capacities of conduction ; 

 we have therefore four equations (in which, according to the law just 

 found, x' = x" = x'" are = x), 



.T = (L + X) /) • sin. I a 



x= (^L+ ^,) p • sin. I a' 



• After I had made the above experiment I saw from No. 5 of PoggendorfTs 

 Annalen, which I had then just received, tliat this last law had already been 

 demonstrated, although in a different way, by Fai-aday. My experiment may 

 therefore serve to confirm it. 



t In the following expressions I consider the resistance I jointly with that 

 of L, since iti the multiplier last employed the conducting wires consisted of 

 one piece with the wire of the multiplier, therefore L -f ?i must always remain 

 constant. 



