11? 



GRAVITATIONAL REPULSION.* 



Francis E. Nipher. 



In a former paper published by the Academy on July 

 28, 1916, the following passage may be found: 1 



" 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 

 into 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 cm. They 

 were hung upon two untwisted threads of silk fibers, 

 forming a bifilar suspension. The length of the threads 

 was 179 cm., and the distance between them was about 

 3.4 millimeters. Near the top of the long metal cylinder 



* Presented by title to The Academy of Science of St. Louis, Oct. 22, 

 1917. 



i Trans. Acad, of Sci. of St. Louis, XXIII, No. 4, p. 173. 



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