GRAVITATIONAL REPULSION.* 
Francis EK. NieHer. 
In a former paper published by the Academy on July 
28, 1916, the following passage may be found:* 
‘“These results seem to indicate clearly that gravita- 
tional attraction between masses of matter depends upon 
their electrical potential due to electrical charges upon 
them.’’ 
Every working day of the following college year has 
been devoted to testing the validity of the above state- 
ment. No results in conflict with it have been obtained. 
Not only has gravitational attraction been diminished by 
electrification of the attracting bodies when direct elec- 
trical action has been wholly cut off by a metal shield, 
but it has been made negative. It has been converted 
to a repulsion. This result has been obtained many 
times throughout the year. On one occasion during the 
latter part of the year, this repulsion was made some- 
what more than twice as great as normal attraction. 
The large masses used in this work were spheres of 
lead ten inches in diameter. They were mounted upon 
blocks of dry wood, which were mounted upon caster- 
wheels provided with roller bearings. The wheels rested 
upon heavy sheets of hard rubber. The suspended 
Masses were two spheres of lead, having a diameter of 
one inch, mounted upon the ends of a brass tube. Their 
distance apart, from center to center was 91.5 em. They 
Were hung upon two untwisted threads of silk fibers, 
forming a bifilar suspension. The length of the threads 
Was 179 em., and the distance between them was about 
3.4 millimeters. Near the top of the long metal cylinder 
a 
— ented by title to The Academy of Science of St. Louis, Oct. 22, 
ele Re 
* Trans. Acad. of Sci. of St. Louis, XXIII, No. 4, p. 173. 
? (177) 
