T H E 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[SIXTH SERIES.] 



DECEMBER 1911. 



LXXXI. On the Amount of the Radioactive Products present 

 in the Atmosphere. By S. Kinoshita, S. Nishikawa, and 

 S. Oxo*. 



Introduction. 



(1) FT is well known that in 1901 Ester and Geitelf 

 JL collected radioactive matter from the atmosphere 

 on a negatively charged wire, in exactly the same way as 

 Rutherford J had done for thorium deposit. This active 

 matter was shown later by Bumstead § to consist of the 

 active deposits o£ both radium and thorium, which originated 

 in the corresponding emanations present in the atmosphere. 

 A number of experiments on this subject have since been 

 made at various parts of the earth's surface, the dependence 

 of the amount of deposits on the meteorological conditions 

 being chiefly investigated. Although this method is supposed 

 not to be suited for determining the amount of the emanation 

 itself, it is the only way of estimating the relative amounts 

 of the radium and thorium emanations in the atmosphere. 

 This has been done by Dadourian || and W. Wilson T, to 

 whose work references will be made later. 



* Communicated by Prof. E. Rutherford, F.R.S., having been read 

 on the 3rd June at the Tokyo Mathematico-Physical Society, 

 t Elster and Geitel, Phys. Zeit. ii. p. 590 (1901;. 

 % Rutherford, Phil. Mag. Jan. and Feb. 1900. 

 § Bumstead, Amer. Journ. Sci. vol. xviii. p. 1 (1904). 

 Ii Dadourian, Le Radium, April 1908. 

 H W. Wilson, Phil. Mag. Feb. 1909. 



Phil. Mag. S. 6. Vol. 22. No. 132. Dec. 1911. 3 I 



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