SECTION III, 1912. [75] Trans. R.S.C. 
A Comparison of the [onization within closed vessels due to Rôntgen and 
Gamma rays. 
By Dre AUS. Eve, E.RS.C: 
(Read May 16, 1912). 
If closed cylindrical vessels, made of various metals, equal in height 
and diameter, and with walls about half a millimetre thick, are exposed 
to the action of Réntgen rays and of the y rays from radium C respec- 
tively, then the results obtained give a comparison of the ionizing effects 
of the two types of rays. 
The results are at first sight surprising. 





Tonizations. 
| | i | | | 
| | | Atomic 
Metal | Thickness | Density | X Rays | 7 Rays Weight 
Ines RER gee Rosemont es 1-8 100 207 
Coppers ees oon eos | = 54! 8-9 | 82 | 69 63-6 
DIG ee Co ie dec. | .44 Zi See | 69 | 65-4 
eae oe Lu 55 ES O0 68 | 55.9 
ATUMIDIUME 5 6 oma eye | -60 2-60 126 58 (751 
Cardboard...0. 0:72 RE AR te | 125 | 49 | 


It will at once be seen that with Rôntgen rays the heavier metals 
permit of less ionization, within the testing vessel, than do the lighter 
metals. But with y rays the metals with the higher atomic weight 
give rise to stronger ionization, within the vessels, than do those with 
lower atomic weight. 
Experimental Details. 
Three different methods were emploved and these gave, broadly 
speaking, concordant results. 
(1) A very thin walled electroscope, supported on light pillars, 
was covered in turn with cylinders, having the upper end closed, made 
of the metals named above. After taking the initial reading the electro- 
scope was covered with the inverted vessel and exposed for a known 
time to the action of X or y rays. The vessel was then removed and the 
fall of potential determined. 
(2) An axial rod was placed in turn within the cylindrical vessels, 
and this rod was connected to a small electroscope above a lid covering 
the vessel. 
