16 
PHYSICS: MILLIKA N AND BARBER Proc. N. A. S. 
by alundum cement. The emittor is thus an equipotential surface. Con- 
centric with this emitting surface is a copper cylinder, s, 1.8 cm. in diameter, 
which will be called grid No. 1. About one-fiftieth part of its surface 
175 
150 
125 
100 
75 
50 
25 
— 
'T 
— - 
' r 
Sir 
Plate Voltnge • 10. "I 
Pressure » fl x 10- a cm.Hg. p~ 
Filament Current ■ 14 ampere* . 
N 
t 
r 
1 
w 
i 
;i3 
iii; 
iii: 
i 
# 
! :'. : 
n 
16 24 
Grid Voltage 
FIG. 5 
32 
40 
is perforated with holes, uniformly placed, 1 mm. in diameter. Just out- 
side this cylinder and insulated from it by quartz or porcelain rings 1 mm. 
thick is a second clyindrical grid, g, the holes of which are slightly larger 
800 
im 
*b 700 
X 600 
s — s 
in 
Vh 
pe 
8 
a 
S 400 
+-> 
g 300 
Plate Voltage 
» 6. 
Preej 
decreaslus 
= 61 10-°or 
^ 200 
Fll-:? 
» 14 amperes, tt 
, ,8 
CO 
s IOO 
1 
ill! 
lih 
( 
3 
I 
2 
3 4 
5 
6 
7 
8 
9 
1 
Grid Voltage. 
FIG. 6. 
(3 mm. in diameter) but exactly match those of grid No. 1. Outside this 
is a third cylinder of copper, 3 cm. in diameter, which will be called the 
plate. The plate can be heated by means of a coil of nichrome wire 
wrapped about it but insulated from it with a soap-stone coating 2 mm. 
thick. 
