166 
MESSRS. W. DE LA RUE AND H. W. MULLER OR THE 
observed. The current was then reversed and similar observations were made. 
Next, for the purpose of making a better examination of the tube in detail, the 
induction plate I was lowered to that distance which gave • as large a deflection 
for the difference of potential between the two ends of the tube as was con- 
venient. After the potentials of the several rings had been measured in succession 
with both currents, the induction plate was restored to its original position, and one 
or two of the first observations were repeated for confirmation. The current was 
then varied by altering the resistance in circuit, 45 ' and fresh measurements made in the 
same order. Thus the following values were obtained : — 
I. Circuit : — 2400 rod-cells, 1 megohm resistance, tube 150. Induction plate at 
2 inches distance from the quadrant. 
Current + 
Differences. 
Current — 
Differences. 
Zero 
6 right = 0 
Full potential (open circui 
t) 154 left =160 I 
. . 1 
200 „ =194 ' 
t 2 
(closed „ 
) 153 or 4 „ =159 j' 
A 7 
198 „ =192 < 
F * • 4 
! ct 
Potential at ring 1 
106 „ =112 J ’ 
. . ‘hi 
133 „ =12 7< 
| 
v j) 2 
96 „ =102 1 
108 „ =102 
„ „ 3 
not observed | 
100 „ = 94 
„ „ 4 
„ i 
95 „ = 89 
,, ,, 5 
” f ’ 
. . 112 
00 
<x> 
II 
00 
CO 
. . . 127 
„ „ 14 
26 left =32 1 
not observed 
„ ., 15 
20 „ =26 [ 
25 right = 19 
„ „ 16 
16 „ =22 j 
20 ,, = 14 
„ „ 1 7 
6 right = 0 J 
6 „ = 0, 
II. Circuit varied by substituting 800,000 ohms for the 1,000,000 ohms of wire, and 
inserting liquid resistance No. 3 (Part I., page 64) between the wire resistance 
and ring 1. 
Current + 
1st Observation. 
2nd Observation. 
Zero 
. 5 right— 0 
5 right = 0 
Full potential (open circuit) 159 left=164 
159 left =164 1 
,, (closed 
„ ) 159 or 8 ,,=163 
158 „ =163 \ 
Potential after 800,000 ohms 139 „ =144 
138 „ =143 j 
„ at ring 1 
112 right=117 
111 „ =116 ■<- 
„ „ 2 
not observed 
103 „ =108 
„ „ 3 
,, 
97 „ =102 | 
„ „ 4 
,, 
90 „ = 95 ] 
„ „ 15 
,, 
25 „ = 30 
„ „ 16 
18 „ = 23 
„ 17 
5 right = 0 
5 right = 0 - 
Mean Differences. 
1 
19-5 
27 
116-5 
* This method of varying the current is arranged to save time. The circuit must not be interrupted 
in the course of a set of observations. 
