Electrical Method for Measurement of Recoil Radiations. 763 



phenomena would necessitate the theory to take into con- 

 sideration the quanta conditions for the energy exchange 

 between atoms and conducting electrons, which seems to be 

 a rather difficult task. However, there are good possibilities 

 for a qualitative understanding of these phenomena. Thus, 

 for example, as we have assumed the electron lattice to he 

 ordinarily in a "fluid'' state, we have a very promising 

 chance to interpret the transition of a metal into a supra- 

 conductor at very low temperatures as the solidifying of the 

 electron lattice, the critical temperature being its melting- 

 point. We thus should adopt for the supraconducting state 

 the ideas used by Lindemann for the interpretation of 

 conduction generally. 



Lund, November 1919. 



LXXXVI. An Electrical Method for the Measurement of 

 Recoil Radiations. By A. L. McAulay, B.Sc* 



General. 



IX the course of a research made with the object of investi- 

 gating soft X radiation produced by the impact of a. rays 

 upon metal targets, it, was found that there was an easily detect- 

 able increase in ionization in a chamber beyond the range of 

 the a particles when they were fired through hydrogen instead 

 of through air. Various tests made to determine the nature 

 of this effect showed that it was due to a stream of hydrogen 

 atoms set in swift motion by collisions with a particles. 

 Sir Ernest Rutherford has investigated this radiation by the 

 scintillation method (Phil. Mag. June 1919), but it was 

 supposed that it would not be measurable by an electrical 

 method, owing to its smallness, and to the large y ray 

 ionization necessarily present near the radioactive sources 

 used. The above results, however, seemed to indicate that 

 by making use of a balance method such recoil radiations 

 might be satisfactorily investigated by the ionization they 

 produce. An electrical method has many advantages over 

 one based on counting scintillations. It does not involve 

 the dark room and eye-strain inseparable from the latter, 

 and owing to the large number of particles effective in one 

 observation, probability variations are negligible, and a 

 smaller number of determinations are necessary to fix a 

 magnitude with accuracy. 



* Communicated by Prof. Sir E. Rutherford, F.R.S. 

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