Absorption of y Rays. 



603 



closed by a thin sheet o£ the same material as the absorbing- 

 sheets. The walls and base, however, were o£ lead 9*5 mm. 

 thick to keep out soft scattered radiations. The windows 

 consisted o£ glass plates 8 mm. thick, which were protected 

 by lead cylinders 9 mm. thick. A very small sulphur bead 

 was used for the leaf-suspension, so that constant readings 

 of the leak were obtained. The experiments were carried 

 out in the centre of a large room, all substances from which 

 scattered radiation might possibly arise being at least 2 metres 

 distant from the electroscope. 



The results are given in Tables I. and II. and shown in 



Table I. — Al Absorbers. 



Hardeners. 



Values of £ X 100. 



None 



9-57 

 3-58 

 3-18 

 3-54 

 2-92 

 2-77 

 2-67 

 2-52 



4-27 

 3-85 

 3-51 

 375 

 3-21 

 315 

 3-01 

 292 



4-23 

 402 

 371 

 3-85 

 3-41 

 323 

 3-22 

 3-15 



4-24 

 4-03 

 3-83 

 396 

 3-61 

 3-41 

 3-30 

 327 



4-23 

 404 

 3-81 

 3-99 

 364 

 3-48 

 3-38 

 335 





2-4 cm. Cu 



2'5 cm. Sn 



•2 cm.Pb 



1-1 cm.Pb 



2-0 cm.Pb 



2-9 cm.Pb 



3'8 cm.Pb 



Thickness of 

 Absorbers, 



•2 



3-4 



66 



9-8 



130 



16*2 cm. 



Table II. — Fe Absorbers. 



Hardeners. 



Values of ^X 100. 



None 



4-o3 



4-28 

 4-21 

 411 

 3-84 

 396 

 353 

 339 

 332 

 3-29 



420 

 4-08 

 4-02 

 389 

 3-98 

 3-67 

 357 

 351 

 3'50 



413 

 4-02 

 4-01 

 390 

 3-97 

 376 

 3-70 

 3-64 

 361 



4-02 

 3 97 

 393 

 3-89 

 396 

 3-78 

 372 

 3-68 

 367 



395 

 394 

 392 

 3-89 

 3-92 

 383 

 3-76 

 3-72 

 3-70 





7*5 cm. Al 



2-4 cm. Ou 



2*5 cm. Sn 



•2 cm.Pb 



11 cm.Pb 



2'0 cm. Pb 



29 cm.Pb 



3-8 cm.Pb 



4' 

 4- 

 3- 

 3- 



291 



2-79 



275 



271 



58 



16 



56 



83 

 3-37 

 3-15 

 307 

 304 



Thickness of 

 Absorbers. 



•2 



1 



2 



4 



6 



8 



10 



12 cm. 



