836 S. Kinoshita, S. Nishikawa, and S. Ono on Amount 



As the direct measurement of the emanation content of 

 the air at Tokyo is at present lacking, it is difficult to assert 

 that Ne is actually smaller here than at the places above 

 mentioned. From the fairly good agreement of the three 

 observations made at the widely different parts of the earth's 

 surface, it might be thought that its value at this locality 

 would be also of magnitude of the order of 1*4. 



(17) There are certainly some errors in the calculation, 

 as, in the actual case, the wires were stretched between the 

 posts quite near the building, and the direction of wind was 

 not always horizontal. But errors due to these causes would 

 not be so much as to account for the observed difference. 



A view, which naturally suggests itself to reconcile the 

 calculated value to the value 1*4 found at the other places, is 

 that the particles of radium A, like ordinary gaseous ions *, 

 do not remain the same, but may come into aggregation 

 with dust particles or become nuclei of condensation of water 

 vapour f , before they are transformed into the atoms of 

 radium B. 



It would not at present be possible to form a definite idea, 

 in what manner and what rate these changes take place. 

 However, when a large number of chances are considered, 

 the rate at which the particles of radium A change from its 

 initial state of formation into radium A', sav, of mobility k', 

 would be proportional to the total number N of the particles 

 of radium A which remain unchanged. Thus considering- 

 together the recombination with the negative ions previously 

 discussed, we get 



rfN > XT 



in which X can be regarded as a constant as long as the 

 atmospheric conditions remain the same. 



Since the atoms of radium A are undergoing disintegration, 

 we have, in the equilibrium state, 



\ E N E = \ A N + \N = (\ A -h\)N, or N=^^- 



A. a + A, 



If k' is very small compared with k or 1*3, the expression 



* Langevin, C. R. p. 232 (1905) ; Langevin and Moulin, Le Radium, 

 p. 218 (1907) ; Pollock, Le Radium, p. 129 (1909). See also Langevin, 

 Ann. Chim. et Rhus. p. 289 (1903) ; Sutherland, Phil. Mag. vol. xxxvi. 

 p. 507 (1893), and vol. xviii. p. 341 (1909) ; Wellisch, Proc. Roy. Soc. 

 vol. lxxxii. p. 500 (1909), and Verh. d. D. Rhys. Ges. p. 159 (1911). 



t Rutherford, < Radioactive Transformations,' p. 207 (1906). 



