398 Proceedings of Royal Society of Edinburgh. [sess. 
tively and the rays played on it. After two minutes the electro- 
meter reading was steady at 0'5 of the initial reading. The elec- 
trometer was then discharged by metallic connection, and again 
charged positively. Its reading remained steady after three 
minutes at 0’63 of the initial charge. In the third and fourth 
experiments the readings after three minutes were *8 1 and ’90 of 
the initial charges respectively. 
The ball was next charged negatively. When the rays were 
played on it a steady reading was obtained after four minutes at 
T8 of the initial charge. In the second, third, and fourth experi- 
ments the steady readings after four minutes were '45, '70, and '78 
of the initial charges respectively. 
§ 6. The paraffin was then removed and the brass ball polished 
with emery paper ; whether the charge was positive or negative, 
it fell in about five seconds to one definite position, 50 scale 
divisions on the positive side of the metallic zero, when the 
Rontgen rays were played on the charged ball. 
§ 7. These experimental results demonstrate that the Rontgen 
rays did not produce sensible conductance between the brass ball, 
when it was coated with paraffin, and the surrounding metal 
sheath ; and that they did produce it when there was only air and 
no paraffin between them. From experiments by J. J. Thomson, 
Righi, Minchin, Benoist and Hurmuzescu, Borgmann and Gerchun, 
and Rontgen,* we know that air is rendered temporarily conduc- 
tive by Rontgen rays, and Rontgen’s comparison of the effect of 
the rays with that of a flame shows that our experimental results 
are explained by the augmentation of the electrostatic capacity 
(quasi-condenser) of the brass ball by the outside surface of its coat 
of paraffin being put into conductive communication with the 
surrounding lead sheath and the connected metals. 
§ 8. In our second experiments we have endeavoured to eliminate 
the influence of the varying capacity of this quasi-condenser. 
For this purpose, we placed a strip of metal connected to the 
* J. J. Thomson, Proceedings R.S.L. , February 13, 1896; Righi, Comptes 
Pendus, February 17, 1896 ; Benoist and Hurmuzescu, Comptes Rendus , 
February 3, March 17, April 27, 1896 ; Borgmann and Gerchun, Electrician, 
February 14, 1896 ; Rontgen, Wiirzburger Phys. Med. Gesellschaft, March 9, 
1896 ; Minchin, Electrician , March 27, 1896. 
