of Radium, and Secondary Rays which they produce. C)47 
Table III. 
Screen belonging to Group I 
Radiator 
and its 
thickness. 
Pb screen. 
Radiator 
and its 
thickness. 
Pb screen. 
1 mm. 
4 mm. 
1 mm. 
4 mm. 
Pb 1-8 mm 
Zn 3 „ 
100 
193 
100 , Pb 1*8 mm 
141 C 20 „ 
100 
240 
100 
178 
Screens belonging to Group II. 
Radiator 
and its 
thickness. 
Fe screen. 
Radiator 
and its 
thickness. 
Fe screen. 
1*3 mm. 4*3 mm. 
1-3 mm. 
4-3 mm. 
Pb 1-Smm 
Zn 6-5 , 
100 100 
252 290 
Zn 6'5 mm 
C 20 „ 
100 
355 
100 
329 
Al screen. 
Cu screen. 
38 mm. 7*5 mm. 
1*6 mm. 
4*6 mm. 
Pb 1'8 mm 
Zn 3 „ 
100 100 
190 224 
Pb 1-8 mm 
Zu 6-5 „ 
100 
329 
100 
355 
Screen belonging to Group III. 
Radiator 
and its 
thickness. 
C screen. 
Radiator 
and its 
thickness. 
C screen. 
4 mm. 24 mm. 
4 mm. 
24 mm. 
Pb 3 mm 
100 100 Zn 6-5 mm 
230 237 C 20 „ 
100 
85 
100 
92 
C 20 „ 
^ " 
C screen. 
4 mm. 24 mm. 
100 100 
207 228 
C 20 , 
2 X2 
