the Hot-wire Anemometer. 



533 



used in the case of 0, N, C0 2 , air. The value of s x is given by 

 Joly (1891)as jjrrO-1715 + 0-02788/0, where p = density of 

 the air in grms. per c.c., and 5 2 = 0'165-f 0'2125/o4-0-34/3 2 

 (Joly, 1894). Applying the appropriate values of p, it 

 is seen that it is quite sufficiently accurate to use the 

 values S]=0*1715 and s 2 = 0*165. We have therefore, since 

 7^=87*5 and V 2 = 100'6 (the numbers are relative and are 

 taken from the diagram), 



Kco, _ 1-2 93 x 0-17 15x87-5 

 Kair ~ 1-977 x 0-165 x 100-6 



This ratio, and the similar ratios of conductivities in the 

 cases of oxygen and nitrogen, are set out in the accom- 

 panying table, together with the values of the ratios at 

 0° 0. and at 350° Q. } the ratios at 0°C. being experimental 

 numbers derived from Winkelmann's observations, and those 

 at 350° C. being calculated therefrom by means of 0. E. 

 Meyer's formula, K=l'603?7^c r , the value of 7) t being calcu- 

 lated by means of: Sutherland's formula *, 



Vt = V 



273 + 



e 



3+c/ o \ 3/2 



+ c \2T6) 



the values necessary for the calculations being all derived 

 from Kaye and Laby's Tables. 



Table VI. 



Gases. 



Values of Ratio of Conductiviti 



Experimentally 



by Flow method. 



At 0° C. from 

 Winkelmann's 

 observations. 



Calculated 

 at 350° C. 



Iv . Carbon dioxide 

 K . Air 



K . Nitrogen 



Iv . Aii 



0-591 

 1-014 



0-588 



1-004 



0-858 



0-9.: 



Iv . Oxygen 



" K . Air 



0-909 



1-078 



1-091 



* Phil. Mag. xxxi. (1893). 



