Radio-active Products present in the Atmosphere. 321 



given, and also values o£ viscosity in other cases, enabling C 

 to be calculated. In the table below I have given the mean 

 value of C for each gas from the Tabellen, and in brackets 

 those values calculated from data given in the Tabellen. 

 Strictly the same sort of correction ought to be applied 

 separately to each of the four methods used by Jeans for 

 finding 2a, but it is practically as useful at the present stage 

 to apply the correction to his mean values obtained from the 

 results ot the four methods. These are given in the 

 second column of the following table under the heading 

 2a(l + C/T)* X 10 8 , the last column giving 2a x 10 8 . Water 



Gas. 2«(l-fC/T)*xlO s . C. 2a x 10 s . 



cms. 

 Hydrogen 203 



cms. 



72 "I -SI 



Helium 1-81 



Carbon monoxide... 2*86 

 Ethylene 3'81 



76 



(156) 

 249 

 110 

 115 



(195) 

 128 

 160 

 258 



(167) 



(199) 



1-60 

 2-28 

 275 

 246 

 2-38 

 215 

 225 

 2*22 

 241 

 2-77 

 313 



Nitrogen 2'91 



Air 2-84 



Nitric oxide 2'82 



Oxygen 2 - 73 



! Aro'on 2*79 



Carbon dioxide 336 



Nitrous oxide i 3'52 



Chlorine | 411 



Water-vapour [ 339 



Ethyl chloride 4"68 



vapour and ethyl chloride at ordinary temperatures are too 

 far from the condition of a typical gas as regards the con- 

 ditions of collision to permit of a satisfactory estimation of C 

 without special experiments and discussion." 



Melbourne, September 1, 1908. 



XXVI. On the Radio-active Products present in the Atmo- 

 sphere. By W. Wilson, M.Sc, Graduate and Hatfield 

 Scholar of the University of Manchester *. 



SINCE the experiments of Elster and Geitel t in 1901, 

 various experimenters working at different parts of the 

 earth's surface have found that a wire suspended in the air 

 and maintained at a high negative potential becomes radio- 

 active. Bumstead % showed that the activity thus obtained 



* Communicated bv Prof E. Rutherford, F.R.S. 

 t Elster & Geitel, Phi/s. Zeit. ii. (1901). 

 X Bumstead, Am. Jour. Sci. 1904. 



