XLVI. A Radioactive Gas from Crude Petroleum. 
By H. F. Burron, B.A.* 
N the course of their investigations on the radioactivity 
of the atmosphere, Elster and Geitel t have shown that 
the soil and rock-masses constituting the surface-layers of 
the earth are the source of an emanation, or gas, which 
gradually escapes into the air, and there exhibits properties 
analogous to the radioactive emanations from thorium and 
radium. In a conjoint paper by Professor McLennan and 
myself { on the conductivity of air confined in receivers of 
different metals, some observations are cited which indicate 
that metals generally are, to a slight degree, the source of a 
similar emanation. This result has since been confirmed 
by Strutt§, who found that air drawn through a glass tube, 
heated just below redness, and containing scrap copper, 
acquired a conductivity three or four times its normal value. 
Strutt§ has also shown that a highly radioactive emanation 
can be obtained by bubbling air through mercury heated to 
about 300° C. 
More recently, Professor J. J. Thomson || established the 
existence of a radioactive gas in the Cambridge tap-water as 
well as in the water from a number of wells in different parts 
of England. Similar results have been obtained by Himstedt] 
at Freiburg, and by Lord Blythswood and H. 8. Allen ** 
with the mineral waters of Bath. Later still Adams tf made 
a careful study of the radioactive gas in Cambridge tap-water, 
and his results, as well-as those of Strutt on the emanation 
from mercury, go to show that the activity in all these cases 
is due to the presence of a substance very similar to, if not 
identical with, the emanation from radium. 
In the following paper an account is given of some experi- 
ments with a highly radioactive gas obtained from crude 
petroleum, which, both in the rate at which its activity decays 
and in the nature of the induced radioactivity it produces, 
very closely resembles the emanations dealt with by the 
investigators just mentioned. | 
Apparatus.—The petroleum used in the experiments was 
* Communicated by Prof. J. J. Thomson, F.R.S. 
+ Phys. Zeit. iii. Jahr. 24, p. 574; Denksch. d. Kommission fiir luft- 
electrische Forschungen, Minchen, 1903. 
} Phil. Mag. vol. v. (June 1903) p. 699. 
§ Phil. Mag. vol. vi. (July 1903) p. 113. 
|| Proce. Camb. Phil. Soc. xii. 3 :(1903) p. 172. 
"| Berichte der Naturf. Ges. von Freiburg ¢. B., 1903, xiii. p. 101. 
** Nature, Jan. 14, 1904, p. 247. 
+? Phil. Mag. vol. vi. (November 1903) p. 563, 
