480 



Dr. H. A. Wilson on the 



In fig. 3 these values of (Vi + V 2 ) are plotted against the 

 corresponding values o£ the current. The curve drawn is 

 the parabola C= l2'8\/V 1 -4- V 2 , an d it will be seen that 

 nearly all the points lie near this curve. It appears therefore 



Fur. 3. 



300 



200 



100 



1 









I 





























/ 















100 



200 



;00 



W0 



500 



600 l/OLTS. 



that the current varies approximately as the square root of 

 (Vi+V 2 ). Hence we have C = B A /V 2 + V 1 nearly, where 



B = 12-8 for the flame used, or V, + V 2 = ^-. 



But 



so that 



Y=-Y 2 + Y 1 + ACd, 

 V=2+A(U 



Prof. J. J. Thomson * has given the theory of the variation 

 of V with C in a uniformly ionized gas. He finds that when 

 the current is far from its maximum possible value so that 

 there is a region between the electrodes where the electric 

 intensity is uniform, then the relation between V and C is of 

 the form Y = aG 2 + bdC, where a and b are constants. The 

 significance of a and b in Prof. Thomson's formula is more- 

 over precisely that which has been deduced above for — 

 and A. B* 



It appears therefore that the conductivity of the flame is 

 due to approximately uniform ionization taking place 

 throughout the region between the electrodes, and, further, 

 that the current is always very far from its maximum 

 possible value even when a P.D. of 600 volts is applied to 

 electrodes only 1 cm. apart in the flame. 



* ' Conduction of Electricity through Gases/ p. 73. 



