Mr Wilson, The Hall Effect in Gases at Low Pressures. 391 
The Hall Effect in Gases at Low Pressures. (Second paper.) 
By Harold A. Wilson, B.A., D.Sc. (Bond.), Clerk-Maxwell 
Student, Fellow of Trinity College. 
[ Read 3 March 1902.] 
The experiments described in this paper are a continuation 
of those described in the paper entitled '* On the Hall Effect in 
Gases at Low Pressures” ( Proc . Camb. Phil. Soc. Vol. XI. Pt. iv.) 
read to this society last October. 
Measurements have been made of the Hall Effect and electric 
intensity in uniform positive columns in oxygen and hydrogen, 
and also of the variation of the Hall Effect along the discharge in 
air at various pressures. 
I. The Hall Effect in Uniform Positive Columns in Hydrogen 
and Oxygen. 
The apparatus used for the measurements in oxygen and 
hydrogen was identical with that described in the paper just 
referred to. The oxygen and hydrogen were obtained by electro- 
lysis of a strong solution of caustic soda prepared by dissolving 
metallic sodium in water. They were dried by calcium chloride 
and then by phosphorus pentoxide. The apparatus was pumped 
out and refilled until the light from the discharge, when examined 
with a pocket spectroscope, did not indicate the presence of any 
impurities in the gas. 
Tables I. and II. contain the results obtained in hydrogen. 
Table I. 
The Hall Effect 
in the Uniform 
Positive Column 
in Hydrogen. 
Pressure. 
Hall Effect. 
Magnetic Field. 
Zp 
(P) 
W) 
(H) 
H 
0T33 mms. 
7*20 volts per cm. 44-2 
2-16 x 10- 2 
0-175 
5-24 
44-2 
2-08 „ 
0-188 
4-82 
45-3 
2-00 „ 
0-275 
3-50 
45-0 
2-14 „ 
0-292 
3-17 
44-2 
2-10 „ 
0-42 
2-02 
40-9 
2-08 „ 
0 53 
1-63 
44-7 
1-93 „ 
0-83 
1-06 
44-2 
1-99 „ 
1-00 
0-95 
47-9 
1-99 „ 
Mean 2 -05 x 10~ 2 
