136 Prof. P. 0. Pedersen on the 



The same holds also for other values of y 

 approximation we can therefore put 



log?=7^-l) • • 



or 



n 



— — e ; 



n 



sufficient 



• (17) 



• (18) 



here 7 is a coefficient which only depends on y. 

 In place of Townsend's relation 



(19) 



n = e ' 

 we thus obtain the equation 



7l a ya(a-l ) 



In the table below are given approximate values of 7 

 calculated on the basis of equations (16) and (17) for values 

 of y between and 0*368 = e _1 , which latter value is the 

 highest y can obtain : — 



y- 



r- 



y- 



r- 



y- 



•00 ... 



.. 1-00 



010 ... 



.. 0-92 



020 



•01 ... 



.. -98 



•11 ... 



... -91 



•21 



•02 ... 



.. -98 



•12 ... 



... -90 



■22 



•03 ... 



... -97 



•13 ... 



... -89 



•23 



•04 ... 



... -96 



•14 ... 



... -89 



•24 



•05 ... 



... -96 



•15 .. 



... -88 



•25 



•06 ... 



... -95 



•16... 



... -87 



•26 



•07 ... 



... -95 



•17... 



... -87 



•27 



•08 ... 



... -93 



•18 ... 



... -86 



•28 



•09... 



... -92 



•19 ... 



... -86 



•29 



85 

 84 

 84 

 83 

 83 

 82 

 82 

 81 

 81 

 80 



y- 



0-30 .. 

 •31 .. 

 •32 .. 

 •33 .. 

 •34. 

 •35 . 

 •36 . 

 •368 



)-79 



•79 

 •79 



•78 

 •78 

 •77 

 •77 

 •76 



5. The determinations of l , V , 7, and a are made on the 



basis of measurements of corresponding values of -° and a, 



and by use of equation (17) as well as the table above. As 

 example, we will treat the following series of measurements 

 by Townsend {loc. cit. p. 277 ; Phil. Mag. (6) vi. p. 598, 

 1903) :— 



Atmospheric air ; Pressure 1 mm. Hg. 

 L = 3'2 x 10- 2 cm. ; X = 350 volt/cm. 



a =0 .... 



. 0-2 



0-4 



0-6 



0-8 



10 



1*1 cm 



^ 1 .... 



. 2-86 



8-3 



24-2 



81-0 



373 



2250 



log- =0 



. 1-05 



2-12 



3-19 



4-39 



5-92 



7-72 



