024 



Mr. D. C. II. Fl 



orance 07? 



by string from a board overhead. Thus care was taken to 

 prevent secondary radiation from surrounding bodies. In 

 these experiments the leak of the electroscope was fairly 

 large, and no difference was observed when the small glass 

 windows were screened by lead. 



Radium (20 nigra. Ka) was placed 56 cms. from the electro- 

 scope. The absorption coefficient was measured for narrow 

 pieces of lead -1 72 cm. thick placed against the radium. The 

 length, breadth, and thickness were (11 X 3'5 X -172)cm. 



Thickness of Screen. 



Tfaicki 



it 

 '172 cm. 



•516 

 ■684 cm. 



•854 



1-04 cm. 



1-38 



1 '55 cm. 



A 



■99 





•70 



•65 



•58 



Prom this experiment it would seem that the lead screen 

 simply cut out the less penetrating 7-rays. 



Compare these results with those; obtained by other 



investigators. 



McClelland*...] 



T!,i ' 



f -8 

 [ 1-05 cm. 



lor, 

 1-3 cm. 



•66 



13 



1-8 cm. 



•48 



1-8 



2-3 cm. 







•44 





64 



Tuomikoski 1 ... 



Thickness 



f -4 



1 1-0 cm. 



10 



2-2 

 5-4 



5-4 



120 



x 



•70 



•58 



•52 



•50 



: E«*i 



Thickness 



f -64 1 21 1-79 

 1 1-21 cm. 1-79 2-36 



24 



30 



•46 



i 



\ 



•57 



•56 



•46 



* Phil. Mag. July 1904. t Phys. Zeit. June 1909. 



Phil. Mag. April 1906. 



As we have seen, 

 for the absorption 

 should be \ = *50. 



A glance at the 

 too large to be ascri 



The radium still 

 lead. A piece (11 

 of the radium and 



Soddy has concluded that the true value 

 coefficient right from the initial stage 



above results shows discrepancies much 

 bed to experimental errors, 

 in the same position is surrounded with 

 x 5x1*4) cm. is placed directly in front 

 lead 1*5 cm. thick placed at the side. 



