Penetrating Radium Rays. 75 
TABLE A. 
I | II Ili. IV 
Welitintin <:..-..<. Cneye) 4 | 
| Mereury..........-. 726 661 538 493 
ear 641 563 ‘480 440 
Dee... 282 266 248 236 
Aluminium ...... "104 104 Fy Oa | 
Ct tes, 087 ‘087 087 ‘087 
7 O34 DS Bric ca ty O84 ny clos 084 
- 
ts ek EME iN Be Lk LE SE aa 0G it 
In this table, for the reason given above, no attempt is 
made to detect any change in the coefficient for water, giass, 
and aluminium. It will be observed that for the heavier 
substances there is a rapid decrease of the coefficient of 
absorption as greater distances of the substance are traversed 
by the rays; no such marked change takes place for the lighter 
substances. 
This points to the conclusion that the y rays are somewhat 
heterogeneous, and that the difference between the coefficients 
of absorption for the more penetrating and the less penetrating 
parts is more marked the greater the density of the substance 
used to absorb the rays. 
Table B gives the result of dividing the coefficient of 
TABLE B. 
I | Il | Iii. IV 
(RIC hr hi) oan | “054 
‘| Mercury ............ | O58. ‘048 039 ‘036 
is See b +056- f= 049 ee hn 08 
ince. | 039 | ‘037 ‘034 | ‘033 
| Atuminiwi  ....,. 7038 | "038 ‘038 | 
Ci aan I, 084 | 034 Os4 fi), 7Op4 
Pivabem oo. i a) 038 bee bia i 08 034 
| hale oe) 
absorption by the density of the substance. It will be seen 
‘than. in column I. the numbers vary considerably, the law 
that the coefficient of absorption is proportional to the density 
not being followed at all closely. The agreement is, however, 
much closer in succeeding columns until in column IV. it 
is very close indeed. For the less penetrating radiation the 
absorption increases more rapidly than the density; but this 
