722 Dr. R. W. Boyle on the Behaviour of 



For some series a constant lias been added to the values of 



A 5 to prevent the different lines falling too close together. 



It will be seen that the values of A 3 for each series fall nearly 

 on straight lines and that the different lines are nearly parallel. 



This shows that A^ + i — A 3 M = C is nearly constant, as was to 

 be expected from the theory. The mean value of is about 

 081. Hence we get /3 = 8, so that the number of electrons 

 per atom comes out about 8 times the atomic weight in all 

 cases. 



This estimate agrees as well as could be expected with 

 recent estimates depending on the scattering of radiation by 

 different elements. 



Since ?z=/5A we have 



'47r\3_ "3 I 



n m+l — H-m- 



ffl' 



By means of this equation it is easy to calculate the number 

 of electrons in successive spherical layers. If we take 

 % = 8 we get the following values of n m : — 



m. n m . -^. 



1 8 l H =1 



2 47 6 Li =7 



3 142 18 Na=23 



4 320 40 K =39 



5 600 75 Rb = 85 



6 1020 128 Cs=133 



The last column contains the atomic weights of the alkali 

 metals, which do not differ very much from the values of 

 njS. Since the calculations made ara only approximate, the 

 agreement is as good as could be expected. 



LXXXY. The Behaviour of Radium Emanation at Low 

 Temperatures. By JR. W. Boyle, M.Sc, Ph.D., 1851 

 Exhibition Science Scholar, McGill University* . 



^f^HE researches of Rutherford f and of Gray and Ramsay J 

 X have shown that at temperatures from —127° C. to 

 104° C. the emanation of radium has definite and constant 

 values of vapour pressure corresponding to every tempera- 

 ture. At temperatures below —127° C. the only knowledge 



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



t Phil. Mag-. [61 xvii. p. 723 (1909). 



t Journ. Chem. Soc. xcv. p. 1073 (1909). 



