I9IS.] BAUER— ATMOSPHERIC ELECTRICITY. 17 



measurements were made of the ionic numbers m+ and n_, and the 

 resuhs indicate that the low values of the conductivity referred to 

 above are to be attributed partly to a low value of the specific 

 velocities of the ions {%\ and v_). The mean values of z\ and v_ 

 for observations on three days in Long Island Sound are respec- 

 tively 0.77 and 0.83 cm./sec. per volt per cm. The average value of 

 11+ and n_ for observations taken on three days in Long Island Sound 

 are 340 and 280 ions per c.c. respectively. 



By making use of the value (23) given above for the radio- 

 active content, and of the empirical relation obtained by Kurz, for 

 the reduction of the Elster and Geitel unit to absolute value, it 

 turns out that the average radioactive content for the whole cruise 

 amounts to about 12 curies of radium emanation per cubic meter as 

 against 80 curies per cubic meter which is about the average value 

 found over land. The emanation content is thus too small to ac- 

 count for the conductivity observed over the sea, which conductiv- 

 ity is as great or greater than that measured over land. 



A criticism of the ordinary method of drawing conclusions as to 

 the nature of the radioactive products in the atmosphere, by com- 

 paring the decay curve with one obtained by a wire exposed in a 

 closed vessel, is given in Dr. Swann's report. The activity curves 

 are analyzed in the report mathematically, use being made of the 

 theory of radioactive disintegration, and it is found that while 

 some of the curves can be explained by radium emanation alone, 

 others require the presence of a product of longer decay period than 

 radium A, B or C. The possibility of this extra product being a 

 product of thorium emanation, as is generally assumed to be the 

 case on land, is discussed by Dr. Swann. 



An attempt to calculate the actual amount of radium emanation 

 in the air directly from the theory of the Elster and Geitel method, 

 without assuming any empirical relation results in a much smaller 

 value for the radium-emanation content than that given by the 

 empirical relation unless it is assumed that the average specific 

 velocities of the active carriers are much smaller than is generally 

 supposed. 



PROC. AMER. PHIL. SOC., LIV. 2l6 B, PRINTED JUNE I9, I915. 



