PHYSICS: HULL AND RICE 
269 
The position of the K Hnes, and their relation to the general radia- 
tion at different voltages, has been studied by means of the ionization 
chamber also. Figure 3 shows the ionization current as a function of 
the angle of incidence of the rays on the crystal, for five different volt- 
ages, and figure 4 a part of the same in the second order. The position 
of the K lines in the first, second and third order respectively, is shown 
by the dotted lines marked ai, ^i, a2, ^2, etc. There is no trace of the 
IOC 
1 \ 
W T/ 
T2 .165 miT 
1 A/aC 
1 BB'CC 
1 
n W PILTER 
. 1 
Y CRYSITM- 
NDAmO THIfPO OROSP< 
t — .a 
/ — lU^ 
nV 
1 
1 
1 
il 
il 
4\ 
ao 
— 
2= 90 
3- ao 
KV/ 
' TT 
\\ 
1 1 
1 
'JO 
M 
III 
In 
1 1 
-H 
1 
1 
1 
60 
/ 1 
/ 1 
1 
> ■ 
A' 
1 
SO 

/.I 
ll 
./ 1 + 
y 1 1 
^ 1 1 
1 
M 
1 
1 1 
1 1 
1 
1 
1 
1 
1 
— n 
1 
1 
' 1 
3 
: 1 
\ 
to 
10 
ASJGLEOF 
CRYSTAL 
0' 
go 
3" 
5" 
FIG. 4 
lines at 70,000 volts, but at 80,000 they are clearly visible, and increase 
in intensity as the voltage increases. It is probable that the lowest 
voltage at which the lines appear is the 'quantum' voltage, i.e., that 
given by Duane and Hunt's equation, for the 7 line, about 70,000 volts 
for tungsten. This would be in harmony with the mechanism of radia- 
tion suggested by KosseP and has already been found by Webster^^ to 
hold for rhodium. It may be mentioned that the quantum relations 
