Gases by penetrating Rontgen and Radium Rays. 615 
760 mms. was found to be a straight line (fig. 5). The 
values obtained were practically the same as those given by 
Strutt, Proc. Roy. Soc. 5th Aug. 1903. 
Fig. 5. 
tt ays. Ar. 
Current 
(@) Zoo 400 6°90 goo 
Fressure 197) mms. 
| Gas. ve | Density. | Strutt. | ee 
| > ee ee es es a 
RM nos tinea a's bax suvwaveces | 1-0 1:0 | 1-0 | 
Es: eee ener 1*2 1:23 
SOTTO © .....0.2 .2..0:.-- | 4°32 4°88 4:8 
| Methyl Iodide ............... 53] | S67 56 | 
| Carbon Tetrachloride ...... | 5°05 4:80 52 
Secondary Radiation. 
‘With the Roéntgen rays there was abundant evidence of 
secondary and tertiary radiation. The block of lead and the 
large and small lead covers effectively screened the upper 
electroscopes. The amount of secondary radiation in the 
lower brass cylinders was proved to be large. A sheet of 
cardboard painted with phosphoric acid reduced the current 
from 100 to 40, two sheets from 100 to 26. The cardboard 
appeared to be an unsatisfactory conductor, and the interior 
of the brass cylinder was therefore coated with sheet 
