Primary and Secondary y Rays. 921 



chemical point of view in pointing ont the existence of 

 chemical relations. Thus if it is found that certain relations 



T 



connect the values of -= of certain chemical compounds, 



V ffl i 



we might expect that some corresponding chemical relations 

 exist. The determination of the critical constants of chemical 

 compounds, especially the critical temperature, becomes 

 therefore of great importance. A more complete list of the 

 critical constants than the one at present available may lead 

 to the discovery of a number of other properties of the 



T 



quantity — ^-corresponding to certain chemical properties, 



V m | 

 besides those given in this paper. 



T c 

 There appears no obvious reason why the quantity — =. 



of a substance should be so closely connected with its 

 chemical properties. We may state this quantity in a 

 different way, but that hardly throws any light on the subject. 

 The kinetic energy of a molecule is proportional to the 

 temperature, and we may therefore define this quantity 

 as the ratio of the kinetic energy of a molecule at the 

 critical temperature to its chemical attraction at a given 

 distance. 



Further relations of the quantity with physical and 

 chemical quantities will be given in subsequent papers. A 

 comparison of the various results obtained will probably lead 

 to a definite explanation why the properties of this quantity 

 run parallel with the chemical properties. 



Cambridge, July 20, 1910. 



CIV. Primary and Secondary j Rays. \ 

 By D. C. H. Florancb, M.A., M.Sc* 



"\T7~HEN 7-rays strike a body it is well known that a 

 TT secondary radiation is produced. Part consists of a 

 corpuscular radiation similar in character to /3-rays ; and 

 part consists of a very penetrating radiation similar in cha- 

 racter to the primary 7-rays. Eve t first proved that these 

 penetrating secondary rays were of the 7-ray type. Kleemanf 



* Communicated bv Prof. E. Eutherford, F.E.S. 

 f Phil. Mag. Dec. 1904. 

 X Phil. Mag. May 1908. 



Phil. Mag. S. 6. Vol. 20. No. 120. Dec. 1910. 3 P 



