188 Trans. Acad. Sci. of St. Louis. 



At 10 :25 a. m., June 2, readings were taken until 10 :43 

 a. m. The suspended masses were at rest. 



The positive terminal was then applied. The result is 

 shown in Plate XLVT. 



The arrangement of the apparatus was that shown in 

 Fig. 3. A sudden decrease in the attraction occurred. It 

 was so sudden that forced vibrations were impressed 

 upon the suspended masses. The vibrations were small, 

 and only occasional readings of consecutive extremes 

 were recorded. At 2:20 p. m. the terminals were re- 

 versed and at 2 :32 p. m. direct contact of the pin-point 

 conductors and the large masses and shield was made. 

 The attraction at once increased very rapidly. The ab- 

 solute zero of potential was reached and passed in a less 

 time than that of a semi-vibration. Forced vibrations 

 were impressed upon the suspended masses as the at- 

 traction began to decrease. These vibrations were ob- 

 served, and the extremes were read until 3 :30 p. m. The 

 masses were then being repelled by a force nearly twice 

 as great as the initial gravitational attraction. Direct 

 contact between the discharge points was removed, but 

 the masses were not grounded. On Monday, June 4, at 

 9:20 a. m., the masses were vibrating over a very small 

 arc (about one scale division). Eeadings were taken at 

 some of the extremes of vibration, which were sufficient 

 in number to show that the mean reading was constant 

 until 11 a. m. These readings are represented in Plate 

 XL VII. The masses were still repelling each other, with 

 a force about 50 per cent, greater than the initial attrac- 

 tion on the morning of June 2. This conclusion seemed 

 beyond belief at the time but subsequent results on that 

 day seemed to make it a necessary conclusion. At 11 :03 

 a. m. the positive terminal was applied and direct con- 

 tact between the large masses and the pin-point con- 

 ductors of Fig. 3 was made. The time is represented by 

 the arrow marked + D. C. on Plate XL VII. 



At once the attraction began to increase. The masses 

 were swaying in the opposite direction at the time when 



