80 
Transactioyis of the Royal Society of South Africa. 
Table I. (Beattys Method.) 
Absorption Coefficients in Various Gases of the Corpuscular Rays produced 
—8 
hy Characteristic Silver X rays. w.l. — "560 x 10 cm. 
Absoiijing gas. 
Total ionisation by com- 
plete absorption of cor- 
puscular rays. 
Values in column II 
relative to air = 1 . 
For comparison with 
column III. 
p^ obtained from 
curves, fig. 3. 
Mean temp. 
a 
o 
CO 
si 
d 
o 
O 
OS 
Density [d). 
5; 
1,B. 102, B P. 
•SOB* 
•00009 
8900 
Air 
•748 
1 
1 
4^12 cm. 
23° C 
9-56 
7410 
' 9-3, Bf 
-00129 
7210 
0., 
•786 
1-05 
110, B.P. 
3 46 „ 
26° 
11^50 
00143 
8040 
•738 
•99 
102, B.P. 
2 32 „ 
23° 
16-97 
•00198 
8570 
so., 
■88 
1^18 
•96, B.P. 
2-30 „ 
22° 
17^06 
•00293 
5820 
Mean — 
7660 
B = Beatty, loc. cit. 
B.P. = Barkla and Pliilpot, ' Phil. Mag.,' [6], June (1913). 
The mean value of ^jd found by Lenard in two experiments on absorp- 
tion in air, two in hydrogen and one in sulphur dioxide was 3774. This was 
for cathode rays having a speed given by a fall through 30,000 volts. By 
using the value for ^jm and the relationship Vk = 10^ A, where is the 
above speed and A the atomic weight of the metal supplying the charac- 
teristic X rays which would produce this maximum speed, it was found that 
rhodium (at. wt. 103) is the approximate metal; it is known also that 
L — constant. In this way I estimate that Lenard's constant would have 
been of the order 3120 had he used cathode rays excited by silver X rays. 
It appears, therefore, that the absorption coefficients in Table I are abnormally 
high. 
It cannot be stated with certainty that Lenard's rays were homogeneous. 
The same is true of the rays employed in these experiments, as will appear 
from Part II of this paper. 
* Estimated from \ = •ol at 15° C. for corpuscular rays from silver produced by 
Sn. X rays, using the relationship \ (at. wt.)^ — constant. 
t Calculated from Beatty 's value 8*8 at 15° C. for Ag. X rays falling on silver. 
Beatty corrected his values to 15° C. and 76 cm. pressure. Subsequent writers quote 
his figures as at 0° C. and 76 cm. pressure. See ' Phil. Mag.,' [6] xx, p. 323 (1910). 
