288 SCIENCE PROGRESS 



radium B and radium C radiations, as the atomic number of 

 the absorber approaches that of the emitting radium product. 



In the Proc. Roy. Soc. (A. vol. xci., A. 629, May), H. Moore 

 continues some work on the corpuscular radiation liberated in 

 vapours by homogeneous X-radiation ; the previous experi- 

 ments have been described in the Phil. Mag. January 19 14, 

 and the two papers show that for carbon, oxygen, nitrogen, 

 sulphur, and chlorine, the number of corpuscles liberated from 

 an atom by a beam of X-rays is the same whether the atom 

 is in combination or not, and this atomic corpuscular radiation 

 is approximately proportional to the fourth power of the 

 weight of the atom ; by combining his work with some earlier 

 results of Barkla, Simons, and Philpot, the author shows that 

 the X-radiation absorbed by an atom of a given element is 

 also proportional to the fourth power of the atomic weight, 

 and suggests that these results, combined with others obtained 

 recently by Bragg and Pierce for elements in the solid state, 

 form a body of evidence for the universal validity of this rule. 

 In a further paper in the Proc. Phys. Soc. London for June, 

 the same author applies these results to the discovery of a 

 method for calculating the absorption coefficients of different 

 substances for homogeneous X-radiation. 



Thermionics. — The Phil. Mag. for June contains a paper 

 by K. K. Smith which is in continuation of some earlier work 

 of Prof. Richardson (Phil. Mag. xxvi. 345 (191 3)]. It ex- 

 hibits the results of an exhaustive series of experiments on 

 the negative thermionic currents from tungsten, and opposes 

 the criticism which has recently been levelled in certain quarters 

 at the usual explanation of such thermionic currents. The 



_b 



author concludes that the formula i = aT n e T has an enormous 

 range of validity, but points out that so far the data obtained 



are unable to decide whether the value n = - or n = 2 gives 



2 



the best agreement with the results. 



Another paper, by Prof. Horton in the Proc. Roy. Soc. 

 (A. 91, A. 629, May), also supports the orthodox view con- 

 cerning thermionic currents, by showing that the emission of 

 electrons from a glowing Nernst filament or glowing lime is 

 independent of the nature of the gas in the discharge tube, 

 and that the apparent increase in the number of electrons 

 emitted at certain gas pressures is really an increase in the 



