174 Trans. Acad. Sci. of St. Louis. 
absolute potential of the earth may be determined. This 
is a problem for the future to solve. 
In the work discussed in this paper an effort has been 
made to eliminate heat effects from all sources. It may 
be that alternating discharges from a high potential 
transformer would produce more marked effects than 
have been observed by the methods above described. The 
surging of negative electrons within the large attracting 
masses would be greatly increased. This would also in- 
volve heat disturbances, the effect of which would cast a 
doubt upon the results. Under the conditions in which 
this work was done the amplitude of vibration of the sus- 
pended masses sometimes changed in a way that 
seemed to discredit the above conclusions. It was fin- 
ally found that variations in the illumination of clouds 
in the northern sky produced marked effects upon the 
position of the suspended masses. The apparatus was 
fifteen feet distant from five large windows in the north 
wall of the room. The variation in radiation from such 
clouds was occasionally followed by a marked change in 
the amplitude of consecutive vibrations. After such dis- 
turbances and others not here referred to had been elim- 
inated, there still remained distinct evidence that the 
value of the gravitation constant as it has been deter- 
mined, is dependent upon the electrical potential of the 
attracting masses, when the effect represented by the 
final term in equation (1) is wholly eliminated by 4 
metal screen. 
Plans are now being prepared which will, it is hoped, 
result in a determination of the change which can be pro- 
duced in the value of the gravitation constant, by elec- 
trification of the larger masses. 
The writer desires to acknowledge the financial aid 
granted to him by the Carnegie Institution of Wash- 
ington. 
