at Low Pressures. 393 



Table IV. 



The Elective Intensity in the Uniform Positive Column 

 in Oxygen. 



Pressure. 

 (p) 



0-139 



Electric Intensity. 

 (*) 



10-3 



X 



sjp~ 

 27-6 



0-31 



15-5 



27-9 



0-37 



16-3 



27-0 



0-40 



17-2 



27-1 



0-44 



17-7 



26-6 



0-64 



20-7 



25-9 



0-85 



24-3 



26-4 

 Mean 26-9 



The Hall Effect and Electric Intensity in oxygen are therefore 



TT _ 



given by the equations Z = 3"79 x 10 -3 — , and X = 26'9 Vp. 



In the previous paper it is shown that in a uniform part of 

 the discharge 



Z=\HX{h-h), 



k 2 and A- x being the velocities of the negative and positive ions 

 respectively due to one volt per cm. Consequently for hydrogen 

 we have 



2Z 2x 2-05 xl0~ 2 ,, _ .„ lA , lr 

 h - h = fig = 28 P = 1-47 x 10- 3 p- 15 . 



This must be multiplied by 10 8 to get & 2 — k x in cms. per 

 second, so that 



PTYlfi 



r sec. 



The value of k 2 — & 2 found in air was 1*42 x I0 5 p~ 1,5 . For 

 oxygen in the same way 



. 7 2 x 3-79 x 10- 3 x 10 8 .. „ 00 1A4 _.. 

 h ~h = ^9 p~ 1 - s = 2-82 x 10* jr 1 *. 



It thus appears that k 2 — k t in the uniform positive column in 

 oxygen is only about one-fifth of /c, — kj in hydrogen or air. 



