McCLeLuand AND Hackurt—The Absorption of B Radium Rays by Matter. 39 
absorbed with a corresponding generation of secondary. The coefficient w is taken 
to be the same for all the radiations primary and secondary ; this assumption is 
justified by previous work. 
In exactly the same way we have 
dr K 
cee a nie © 
or 
OF =~ ah + br (1) 
and 
= =ar— bh (2) 
where 
TS /b (1 — +) 
and 
ee es 
i 2 
From (1) and (2) we get 
aR i 
de = (a an b*) Rh, 
2p 
ao = (@ — D’)r. 
For values of « less than unity we have 
R = Age aee® A Ae? - b2 
ss ’ 
and 
=a Be~"?- b? IL Brew’ -” 
For a plate thick enough to transmit no radiation, we have 
Ra Rgrne — 0? 
The coefficient of absorption of the total radiation passing through the plate, 
partly primary and partly secondary, is 
Jib = or p/l—k. 
The ¢rue coefficient of absorption for any specified set of particles is the 
quantity p. 
Ht 2 
