The Law of Molecular Attraction. 48)J 



4. Polonium and the active deposit of thorium emit a 

 radiation which is completely absorbed by 0*64 xlO -4 cm. 

 of aluminium. This radiation causes the emission of elec- 

 trons from metals which it strikes. It consists of two portions, 

 one of which is primary and not appreciably affected by an 

 electric field ; the other is secondary and consists of 

 electrons whose velocities range from less than 3*8 x 1(T to 



more than 244xl0 8 '. Wertenstein has found that RaC 



sec. 



emits similar soft radiations, which ionize a gas; he attri- 

 butes the primary radiation to the recoil atoms. 



5. The secondary radiation is emitted not only by the 

 source, but by any object on which a-rays are incident. The 

 electrons of which it consists have considerably higher velo- 

 cities than the S-rays hitherto recognized. 



6. A part, at least, of the ordinary S-radiation is due, not 

 to the direct action of the a-rays, but to these secondary 

 rays. So far as can be concluded from the present experi- 

 ments, it is quite possible that the whole of the S-ray effect 

 may be thus produced. 



Sloane Laboratory, Yale University, 

 June 4, 1912. 



XLV. The Law of Molecular Attraction. 

 By J. E. Mills *. 



DR. R. D. KLEEMAN at first f proposed an inverse 

 fifth power law of molecular attraction. It was 

 pointed out J that this law was not at all in agreement with 

 the facts, and he then claimed § that an inverse seventh 

 power law gave an equation, 



^ 2 _ D -i = constant, .... (1) 



which was in as good agreement with the facts as an 

 equation, 



j y 



^—^ = constant, .... (2) 



derived by the author from an inverse square law of 



* Communicated by the Author. 



t Phil. Ma^r. xix. p. 795 (1910). 



X Mills & MacRae, Journ. Amer. Chem. Soc. xxxii. p. 1175 (19] 0). 



§ Phil. Mag-, xx. p. 678(1910). 



