THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. XIX. — The Probable Influence of the Soil on Local 

 Atmospheric Radioactivity ; by James Cox Sander- 

 son, B.A.* 



Introduction. 



Through the investigations of Elster and Geitelf attention 

 was first called to the fact that the ordinary atmosphere 

 normally contains radioactive constituents which can be col- 

 lected by suspending a negatively charged wire for some time 

 in the open air. Their experiments also showed that the air 

 of cellars and caves contains a relatively greater proportion of 

 radioactive material than the free air above ground, which 

 suggested the possibility that the radioactive substances in the 

 air might be of subterranean origin. The work of other inves- 

 tigators along the same lines has contributed largely to the 

 extension of our knowledge of the nature and origin of atmos- 

 pheric radioactivity. 



Bumsteadif; collected the active deposit upon a long wire, 

 stretched in the open air and charged to a high negative poten- 

 tial. He was the first to show conclusively that the atmos- 

 pheric radioactivity was due in part to the presence of radium 

 emanation and its disintegration products, and in part to the 

 emanation and the disintegration products of thorium. 



Gockel§ has examined the problem from the meteorological 

 point of view and has found very considerable variations in 

 the atmospheric radioactivity to exist with rising and falling 



* Thesis presented to the Faculty of the Graduate School of Yale Univer- 

 sity, June, 1911, for the degree of Doctor of Philosophy. 



fPhys. Zeitschr. ii, 590, 1901. % This Journal, xviii, p. 2, 1904. 



§Phys. Zeitschr., iv, 604, 1902-3; v, 591, 1904; ix, 304, 1908; ix, 907, 

 1908. 



Am. Jour. Sci. — Fourth Series, Vol. XXXII, No. 189. — September, 1911. 

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