402 Proceedings of Royal Society of Edinburgh. [sess. 
ends still pressed together, and it was found that when held as 
near as possible to the metallic disc without touching it, no read- 
ing was produced on the electrometer. After this they were 
separated and tested separately ; and it was found that B, when 
held over the disc, gave a large reading in the same direction as 
before it had been passed through the flame, and A (which was 
previously non-electrified) gave a reading of about the same 
amount in the opposite direction. 
The same results were obtained when Rontgen rays were sub- 
stituted for the flame. 
The explanation clearly is this : the flame or the Rontgen rays 
put the outer paraffin surfaces of A and B temporarily in con- 
ductive communication with the tinfoils, but left the end of B, 
pressed as it was against the end of A, with its charge undis- 
turbed. This charge induced an equal quantity of the opposite 
electricity on the outer surfaces of the paraffin of A and B between 
the tinfoils ; half on A, half on B. 
When the application of flame or rays was stopped, this electri- 
fication of the outer paraffin surfaces became fixed. B, presented 
to the electrometer, showed the effect of the charge initially 
given to its end, and an induced opposite charge of half its 
amount on the sides between the end and the tinfoil. A 
showed on the electrometer only the effect of its half of the 
whole opposite charge induced on the sides by the charge on 
B’s end. 
We have here another proof that paraffin is not rendered largely 
conductive by the Rontgen rays. Had it been made so, then the 
charge given to the end would have leaked through the body of 
the paraffin to the outside, and have been carried away either by 
the tinfoil or by the conductive air surrounding the non-tinfoiled 
parts. 
To show that the induced charges were fixed on the sides, the 
two sticks, A and B, were next coated with tinfoil throughout 
their whole length, only one end of each being uncovered. The 
uncoated end of B was then charged and pressed against that of 
A, and the two were held either in the flame of a spirit-lamp or 
in the Rontgen rays. When taken out of the flame or the Rontgen 
rays, and then separated and tested separately, it was found that 
