214 
Mr.  1ST.  R.  Campbell  on  the 
lation  was  assigned  to  the  metal  under  investigation.     We 
now  know  p',  v\  and  A. 
Fig.  15  shows  the  nature  of  the  agreement  attained,  and 
also  the  difference  between  formulae  (7)  and  (7').  (V)  is 
the  complete  line,  (7)  the  dotted  line. 
Fiar.  15. 
>^ 
■^S-* 
r     ' 
<     i 
OS 
<y* 
0-8 
/ 
// 
/ 
07 
// 
0-6 
OS 
h) 
[' 
C 
implt 
tc  lir 
e  y= 
,-e~< 
* 
07/ 
DJ 
d 
Wed 
line  - 
y+i 
k-< 
H» 
-]Llf 
v] 
'  1 
0-4 
Ac 
P   0-3 
0-2 
/' 
/ 
0-1 
0  /  8  3         4  5         6         7 
9         10        II 
12       13 
Since  only  two-thirds  of  the  external  radiation  was  cut  out 
by  the  screen,  the  curve  (A)  must  contain  half  the  effect  of 
the  agents  (4),  (5),  and  (6),  as  indicated  by  curve  (C). 
Hence  from  each  ordinate  of  (A)  half  the  corresponding 
ordinate  of  (C)  was  subtracted;  the  resulting  curve  (E) 
(equation  8)  gives  the  effect  of  (1)  and  (2)  only,  the  intrinsic 
radiations.  From  this  curve  p  and  v  can  be  found  imme- 
diately, and  by  subtracting  vx  all  through  the  curve  (F) 
drawn,  whose  equation  is 
zPx=*P 
r1_£/3    i,  ni 
a  \4       2     °a/J 
This  was  compared  graphically  with  the  curves  drawn 
from  formula  (7)  for  different  values  of  a;  one  value  was 
always  found  to  agree  fairly  well  with  the  experimental 
results,  and  was  accordingly  assigned  to  the  corresponding- 
radiation.     We  now  know  p,  v  and  a. 
Fig.  16  shows  a  case   of  good   agreement,  and  fig.  17  a 
