Gases by penetrating Rontgen and Radium Rays. 611 
Gas, Dea | ie Bove | aa? | 
ae | 
0D co nae Ae 1 } | 1 | 
gee... 12 | ad 
MIORGIOPNE 22)... 22.2... 0s500 4°3 49 | 32 | 
Methyl Iodide .......:....... 50 4°8 | 72 | 
The values in the right column were found with soft rays, 
and it has been noted that the results obtained varied con- 
siderably with the type of bulb employed. Professor 
Rutherford suggested that the more penetrating rays from a 
hard bulb might give figures approximating to those obtained 
from y rays. Some preliminary experiments confirmed this 
forecast, and a short account of them was forwarded to 
‘Nature, 10th March, 1904, to which Rutherford added a 
_ letter on the theoretical explanation of the results. 
Apparatus. 
A large hard bulb was employed with a powerful in- 
duction-coiland W ehnelt interruptor. 
Fig. 1. Two electroscopes were placed at 
equal distances, about 60 cms., 
from the focus of the _ bulb. 
Hach electroscope was completely 
covered by a removable lead vessel 
1-7 mm. in thickness. In the earlier 
experiments trouble was caused by 
some of the gases attacking the 
leaves of the electroscope. The 
apparatus used was therefore modi- 
fied to the form shown in figs. 1 
and 2. The lower vessels were 
brass cylinders with zine ends, 
measuring 12 cms. in diameter, 
13 cms. in height, and 1°8 mm. 
in thickness. Brass rods along the 
axes of the cylinders were insulated 
by ebonite corks and passed up- 
wards into small _ electroscopes, 
5°5x4x9ems. These were covered 
by lead pots 1:7 mm. thick. The large and small lead covers 
were used whilst the bulb was running, and were removed in 
order to take the readings. The upper electroscopes were 
