654 



Mr. G. Shearer on the 



In the case of hydrogen, as the absorption is negligible, the 

 mean value is I . 



If i be the measured ionization, i' the corrected ionization 

 for a beam of mean intensity I , then 



Xd, 



or 



i 

 i 



Xd 



i. 



The value of A. for air at N.T.P. has been measured by 

 Barkla and Collier*, and the value of the absorption co- 

 efficient at any pressure p cm. and any temperature T° Cent. 



is 



273 



A.. 



76 " 273 + T 



Hence we can correct the curves obtained in the case of air 

 and obtain a value for the relative ionizations of air and 

 hydrogen under the same conditions. 



Table V. 



Ionizatic 



n of H 2 



Relative Ionization by Cu Hays 



Ionization of Air 



Relative Ionization by iSn Rays 



Cn Kays. 



Sn Bays. 





•0003 (?) 



•0063 





•0010 



•0010 





•0024 







•0016 



... 





•0010 







•0016 



•0026 





•0017 



•0060 



0-28 



•0014 



•0030 



0-47 



0025 



•0046 



0-54 



•0025 







•0019 



•0036 



0-53 



•0031 



•0029 



T07 



■0023 



•0034 



0-68 



•0023 



•0039 

 •0009 

 •0013 



059 



... 



•0031 

 •0033 

 •0036 





•0009 



... 





Mean = -0018 



Mean = -0035 



Me an =0 "59 



The rays used were those characteristic of copper and tin, 

 and the results obtained are given in Table V. On some 

 * Phil. Mag. June 1912. 



