180 Trans. Acad, Sci. of St. Louis. 
When the large masses are in place 
i, 2 | i 
\ D+20G 
Here D is the directive constant of Eq. (1), b the dis- 
tance between the centers of the two suspended masses 
m’, and r the distance between the suspended masses and 
the large masses M. The equivalent of the brass rod is 
included in m’. 
When the large masses are electrified, if the time of 
vibration is increased to TJ. and we assume that this is 
due to a decrease in the value of the gravitation con- 
stant G, then 
(2) 
Mm’ 
T2 
T, = 2 I 
\D +206 (1— 
ana) 
1007.7" 
From these equations 
Re: TT T? 
10 0 Te. 
The time of vibration was determined by means of a 
chronograph belonging to the department of astronomy 
of the University. The key was snapped when the mean 
reading passed the cross-hair of the telescope. The 
mean reading was obtained from the reading of the four 
extremes of the two complete vibrations which immedi- 
ately preceded. The values here given are the mean of 
six complete to and fro vibrations and the probable error 
does not in any case exceed 0.25 see. 
Observations March 10, 1916. 
T = 623.0 see. 
£ 1 = 614.5 sec. 
T, = 625.0 sec. 
Rn 
By Big. 4 198 
| 100 
