1038 Mr. Shenstone and Prof. Schlundt on the Number 



such energies of combination well known to the chemist. 

 Considering the character of the atoms described in the first 

 part of the preceding paper, it is not difficult to understand 

 that this energy may have a positive sign in some cases and 

 a negative sign in other cases. Assuming that these views 

 represent the truth of the matter, it is not difficult to see why 

 such results as fill Thomsen's extensive work on Thermo- 

 chemistry have never been successfully connected as yet 

 with any sound theory. At the same time it revives a hope 

 ■that this vast store of experimental evidence may soon be 

 correlated with theory. 



The important conclusion has been reached in this paper 

 that the chief result in obtaining stable equilibrium for the 

 two atoms of the molecule is independent of the special form 

 of any electrodynamieal theory, as for example the Saha or 

 the Lorentz theory, since it depends chiefly upon the electro- 

 static force. All theories agree in making the electrostatic 

 force between infinitesimal elements of charge follow the 

 inverse square law. 



Cleveland, Ohio. 

 Nov. 1,1921. 



'CXI. A Determination of the Number of a-Particles per 

 Second emitted by Thorium C of known y-Ray Activity. 

 By Allen G. Shenstone, M.A., and Professor Herman 

 Schlundt *. 



RECENT experiments in the Cavendish Laboratory by 

 - Sir Ernest Rutherford and others have involved the 

 use of the long-range ^-particles from thorium C. The 

 activity of the large thorium C sources used in those experi- 

 ments was measured, as is customary, by means of a 7-ray 

 electroscope. It h;is therefore become necessary to make 

 an accurate determination of the number of a-particles 

 emitted per second by thorium C of known 7-iay activity. 

 Since that number is known for radium C, a direct com- 

 parison by count and by activity of radium C and thorium C 

 will fix the number of a-particles per second emitted per mg. 

 of thorium C. We have jointly carried out the experimental 

 determinations. 



Thorium C and its products produce, in the course of dis- 

 integration, a-rays of ranges 8*6 cm. and 5"0 cm. in air, in 

 the proportion of 65 to 35. At the same time they produce 

 hard 7-radiation. Radium C similarly emits hard 7- radiation 



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



