Radiation  from  Ordinary  Materials. 
217 
§11.  In  Table  II.  the  following  quantities  are  given :  — 
s,  the  number  of  ions  produced  per  sec.  by  the  intrinsic 
absorbable  radiation  from  1  sq.  cm.  of  the  surface  of  the 
metal,  when  totally  absorbed  in  air.  (The  ionic  charge  is 
taken  as  3*1  x  10-10  electrostatic  units.) 
s\  the  number  of  ions  produced  per  sec.  by  the  easily 
absorbable  secondary  radiation  from  1  sq.  cm.  of  the  metal 
under  the  conditions  of  the  experiment,  when  the  radiation 
is  totally  absorbed  in  air. 
V,  the  number  of  ions  produced  in  1  c.c.  by  the  intrinsic 
penetrating  radiation  from  the  whole  box  (and  the  lead 
screen) . 
V',  the  number  of  ions  produced  in  1  c.c.  by  the  external 
radiation  and  the  penetrating  secondary  radiation  excited  by  it. 
a,  Bragg's  constant  for  the  intrinsic  absorbable  radiation. 
\,  the  absorption  coefficient  of  the  easily  absorbable  secon- 
dary radiation. 
To  find  s  from  p  of  curve  (E)  we  must  divide  by  the  total 
area  of  the  ends  of  the  wire-gauze  cage.  This  area  is 
2  x  182  cm.2 ;  but  since  a  few  ions  are  probably  dragged 
through  the  meshes  of  the  gauze,  the  effective  area  was 
taken  slightly  larger  =  700  sq.  cm. 
To  find  s'  from  p'  of  curve  (C)  we  must  divide  by  the 
same  area  and  multiply  by  1|,  sine  e  p'  gives  only  two- 
thirds  of  the  secondary  radiation. 
Y  =  v  of  curve  (E). 
Y/=|w/  of  curve  (C),  since  that  curve  only  denotes  two- 
thirds  of  the  secondary  radiation. 
Table  II. 
Material. 
Lead  (1)... 
Lead  (2)... 
Copper  (1)... 
Copper  (2)... 
Aluminium  . 
Tin 
Silver  
Platinum    ... 
Gold   
Zinc    
Iron    
§ 
§• 
s. 
,'. 
V. 
V. 
a 
X 
^~?,2. 
Pv-Pi. 
;  270 
0 
V1 
Pi 
10-2 
142 
12-0*  } 
12-5t  i 
•39 
0 
!  260 
0 
13-4 
26-3 
12-5*  1 
12-Ot  J 
•44 
0 
103 
160 
2*2 
22-0 
9-0 
0-6 
•47 
•29 
!  110 
91 
8-L 
27-4 
9-0 
0-5 
•51 
•29 
!H7 
0 
14-8 
17-0 
6-0  *  | 
6-5 1 J 
•36 
0 
!  144 
156 
31 
18-9 
9-0 
0-5 
•57 
•35 
146 
146 
255 
170 
8-5 
09 
•27 
•33 
74 
411 
17-3 
14-1 
120 
0-4 
•30 
■r^ 
78 
169 
10-4 
16-8 
100 
0-6 
•43 
•46 
72 
51 
15-4 
16-8 
10-0 
0-5 
■33 
•28 
119 
124 
12-3 
10-5 
130 
05 
•31 
•34 
*  Calculated  from  "  screened  "  curve. 
,,  „     "  unscreened  "  curve. 
Sco£14^S\ 
