PROCEEDINGS AND TRANSACTIONS OF THE ROYAL SOCIETY OF CANADA. SECOND SERIES--VOLUME VII MEETING OF MAY, 1901 FOR SALE BY JAMES HOPE & SON, OTTAWA; THE COPP-CLARK CO. (LIMITED), TORONTO BERNARD QUARITCH. LONDON, ENGLAND 1901 _EDITOR OF TRANSACTIONS._ SIR JOHN BOURINOT, K.C.M.G., LL.D., D.C.L., Lit. D. (Laval), _Honorary-Secretary. _PRINTING COMMITTEE._ DR. S.E. DAWSON. DR. GEORGE STEWART, SIR JOHN BOURINOT. IV.-The New Gas from Radium. By E. Rutherford, 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 phosphorescent, and if left in for some time, rapidly blackened them. The gas itself was powerfully radioactive, _i.e._ it continuously gave out a type of Röntgen 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.