SECTION III., 1901. [21] Trans. R. 8S. C. 
IV.—The New Gas from Radium. 
By E. Rurerrorp, M.A., D.Sc. 
Macdonald Professor of Physics, McGill University, Montreal ; 
AND 
Miss H. T. Brooks. M.A. 
(Read May 23, 1901.) 
In a recent number of the Comptes Rendus, an account was given 
by Curie of the evidence of the existence of a new gas from radium, 
which possesses remarkable physical properties, A specimen of very 
radioactive radium was placed in a glass vessel connected with a mercury 
pump. On exhausting to a low vacuum and allowing the apparatus to 
stand, the pressure steadily increased. When the very small volume of 
gas thus collected flowed along the glass tubes, it rendered them phos- 
phorescent, and if left in for some time, rapidly blackened them. The 
vas itself was powerfully radioactive, 7.e. it continuously gave out a type 
of Réntgen rays, which made gases partial conductors of electricity and 
rapidly acted on a photographic plate. This gas preserves its radioactive 
power for several weeks. 
For some time past, one of the authors had been independently 
investigating one of the most remarkable properties of radioactive 
substances, namely, the power of continuously emitting radioactive 
particles of some kind. The term “emanation” was applied to the 
substance thus emitted, as there was no evidence at the time whether the 
material emission was a vapour of the substance, a radioactive gas, or 
particles of matter each containing a large number of molecules. 
The “ emanation ” from thorium compounds was shown to retain its 
radioactivity for several minutes and possessed the remarkable property 
of causing every substance in the neighbourhood of the thorium to become 
itself radioactive for several days. The specimens of impure radium 
then in the possession of the author, did not possess the power of 
emitting such an emanation; but Dorn, using a later and more active 
preparation of radium, showed that it possessed the same emanating 
power as thorium. One of the most interesting properties of excited 
radioactivity is that it can be concentrated in an electric field on the 
kathode, so that a very fine wire of any metal can be made to act like a 
powerfully radioactive substance for several days. 
A short time ago, one of the authors published an account of the 
effect of temperature on the emanating power of radioactive substances, 
in the Physikalische Zeitschrift. In the p'per it was shown that the 
