304 Frof. E. Edlund on Unipolar Induction, 



as connected with the body's own molecules, there exists free 

 gather between those molecules; and the quantity of free aether 

 contained by the entire body must be equal to the quantity of 

 aether contained in a volume of vacuous space equal to that 

 of the body. This is what takes place as long as the body is 

 at rest. If, on the contrary, the body is put in motion with 

 the aither which it contains, not only the repulsion of that 

 aether, but also the attraction of the molecules belonging to 

 the body upon an exterior aether molecule at rest is modified, 

 and that in virtue of the established principle that " every 

 thing that takes place or is effected in nature requires a Certain 

 time." But, as I have already pointed out, it does not at all 

 follow from this principle that the modification which the at- 

 traction between the material molecules and the exterior aether 

 molecule undergoes in consequence of the motion must be 

 equal to the modification of the repulsion between the aether 

 molecules contained in the body and the same exterior molecule. 

 On the contrary, I have positively expressed the opinion * that 

 the action between different kinds of molecules is also different 

 in this respect. Let us now suppose that d (fig. 8) represents 

 an element of a circuit containing the quantity m of free aether 

 and a quantity m of condensed aether, and that this element, 

 with the aether contained in it, moves with the velocity h in 

 the direction indicated by the arrow. We at the same time 

 suppose that m x is an exterior aether molecule at rest, that the 

 angle between the right line which joins d and m x and that of 

 the direction of velocity is 0, and that the distance between 

 the molecule mi and the element d is equal to r. The repul- 

 sion between m and m x is then, according to the memoir cited, 

 expressed by 



_ !!™1 (I -ah cos 6 - f M 2 cos 2 6 + ikh 2 ) J 



and the repulsion between the condensed aether m and m x 

 will be 



_momi ^ _ ah cog 0_ j M2 cog2 Q + p A2 ^ 



Using % and k to denote new constants, the attraction 

 exerted upon m x by the material molecules can be expressed by 



+ m^i ^ _ a j t cog 0_|j. o/l 2 cos 2 e + p Q ^ t 



The sum of these three expressions indicates the action of 

 the whole of the element d upon the aether molecule m x . 

 Nothing is known beforehand about the ratio existing 



* Op. cit. p. 72. 



