2896-97.] Electrification of Air by Rontgen Rays . 
393 
Experiments on the Electrical Phenomena produced in 
Gases by Rontgen Rays, by Ultra Violet Light, and 
by Uranium. By Lord Kelvin, G.C.V.O., F.R.S., etc. 
etc.; J. Carruthers Beattie, D.Sc., F.R.S.E., 1851 Exhi- 
bition Scholar, Research Fellow of the University of Glasgow ; 
and M. S. de Smolan, Ph.D,, Research Fellow of the 
University of Glasgow. 
(Read December 21, 1896.) 
Art. I. — Electrification of Air by Rontgen Rays. 
§ 1. To test whether or not the Rontgen rays have any electri- 
fying effect on air, the following arrangement was made. 
A lead cylinder 76 cms. long, 23 cms. diameter, was constructed; 
and both ends were closed with paraffined cardboard, transparent 
to the Rontgen rays. Outside the end distant from the electro- 
meter (see diagram 1 ) a Rontgen lamp * was placed. In the other 
end two holes were made, one in the middle, through which 
passed a glass tube (referred to below as suction pipe) of sufficient 
length to allow the end in the lead cylinder to be put into any 
desired place in the cylinder. By means of this, air was drawn 
through an electric filter f by an air pump. The other hole, at a 
little distance from the centre, contained a second glass tube by 
which air was drawn through india-rubber tubing from the open-air 
quadrangle outside the laboratory. 
In one series of experiments the end of the suction pipe was 
kept in the axial line of the lead cylinder at various points 10 cms. 
apart, beginning with a point close to the end distant from the 
Rontgen lamp. 
In every case the air drawn through the filter was found to be 
* The Rontgen lamp was a vacuum vessel with an oblique platinum plate 
(Jackson pattern). 
t Kelvin, Maclean, Galt, Proc. Roy. Soc , London, March 14, 1895. 
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