WITH MAGNETISM AND ELECTRICITY, l?! 



= — — . rX. 



c 



This, according to the principles of mechanics, expresses the in- 

 crease of velocity which would be imparted to each ponderable 

 unit of mass if it were connected with the unit of electricity, in 

 the time during which the magnetizing force increases from 

 X = to X = X. Let 6 denote the unknown small fraction of 

 the mass of the ponderable unit which the unit of electricity 

 forms, then the above value divided by e gives the velocity u of 

 the current originated by the given increase of the magnetizing 



4 

 force. If this velocity u be multiplied by — e, where e denotes 



the quantity of electric fluid, referred to the electric unit of 

 measure, which exists in each unit of length of the circular path, 

 we obtain the intensity of the induced circular current according 

 to the pure electro-dynamic unit of measure ; and when nmlti- 

 plied by \/2, we obtain it in terms of that unit according to which 

 a current of the intensity 1, while passing round the element of 

 surface, is equivalent to the unit of magnetism, namely, 



.rX. 



cce 



The electro^magnetic moment of this induced circular current 

 (molecular current) is found by multiplying the intensity of the 

 current by the area enclosed by the circular path, and is 



cce 

 We have here assumed that the normal to the plane of the cir- 

 cular path is parallel to the direction of the magnetizing force, 

 which can only be the case for all circular paths by one particular 

 arrangement of the molecules. In the case of bismuth we do 

 not assume such an arrangement, but simply, in accordance with 

 the idea of homogeneity, that the normals to the planes of the 

 circular paths have no paramount direction. According to this, 

 the number of circular paths whose normals make an angle (f> 

 with the direction of the magnetizing force, must be proportional 

 to sin <^. The intensity of the current will then be proportional 

 to cos </), and the component of the moment parallel to the mag- 

 netizing force, to cos <f>^. If, therefore, we multiply the above 

 value by sin <f> cos <^^, we obtain an expression proportional to 



