Prof. Thomson, On the Electric Theory of Gravitation. 69 



of some delicacy unless we have recourse to the atomic theory of 

 electricity, and define an unelectrified body as one which contains 

 equal numbers of positive and negative units of charge. 



The weight of a body on this view depends only on the charges 

 of electricity it contains, thus if we suppose an atom of hydrogen 

 to contain one positive and one negative charge, the weight of an 

 atom of hydrogen would only be twice that of a corpuscle which 

 contains one negative unit, but the mass of the hydrogen atom is 

 1700 times that of the corpuscle, hence the acceleration of the 

 corpuscle under gravity would be 850 times that of an atom of 

 hydrogen, or 850 x 981 ; if the atom of hydrogen contained n 

 units of positive and n of negative electricity the acceleration of 



the corpuscle would be - 850 x 981, hence on this view we should 

 ^ n 



expect the acceleration of the corpuscle under gravity to be very 



much greater than that of ordinary matter. At present the 



detection of an acceleration of the corpuscle as great even as 



850 X 981 would seem to be beyond the powers of known methods, 



but not so much beyond as to preclude the hope that with such 



improvement as we may reasonably expect in the manipulation 



of slow cathode rays it may ultimately be capable of investigation. 



