190 Trans. Acad. Sci. of St. Louis. 



modified form of the apparatus used by Boys will be re- 

 quired. The necessity for such a construction seems to 

 be justified by the evidence already obtained, that if the 

 potential of either of the attracting masses M and m' is 

 zero absolute, gravitational attraction between them will 

 not be affected by varying the potential of the other 

 mass. The gravitation, constant as it has been deter- 

 mined by methods which made use of some form of the 

 Mitchell-Cavendish apparatus, would have a maximum 

 value when either or both of the masses had a potential 

 of zero absolute. 



Neglecting the inductive effect which electrified masses 

 have upon each other, it is possible that the amended 

 equation for gravitational attraction between them is 



It seems possible that the effect of the charges Q and 

 Q' upon gravitational attraction between the masses m 

 and m' may be a surface effect. If so the values of Q 

 and Q' may be replaced by RV and R' V, where R and 

 R' are the radii of the two masses and V and V their 

 potentials due to those charges. 



The above equation may also be written 



ram' 



A - K ( 1 ~m) 



Here it is assumed that the masses are so electrified as 

 to diminish their normal attraction for each other by n 

 per cent. From these two equations the values of m and 

 m' being replaced by their values in terms of volume and 

 density. 



v n 1 6 »» fn .R 2 R' 2 



K ~ K 100 9 VV 



If this equation really represents the conditions im- 

 posed upon the masses, it appears that for any given de- 

 crease in gravitational attraction the potentials of the 

 masses must be directly proportional to the surface areas 



