178 T. S. Taylor— Retardation of " Alpha Rays." 



the thin foil when near the polonium and when farther away 

 from it would scarcely be detected by measuring directly the 

 air equivalents in the two positions. This is probably the 

 explanation of the above statement by McClung, Levin and 

 Rutherford, since their determinations were made in this 

 direct way. 



i-i 



1-0 



0-9 



0-7 



0-6 



0-5 













RF 



% ^ 





•a 















p~ 



-^'" 















x - 



** 

 S 







XJ 

































^ 



































A Plr 



















02 



b> — 















J& 



y^- 



















































J^- 



















AJ 



U— 

















A(h 



) 





































1-8 



i-3: 



2-17 



2-57 



2-97 



Fig. 4. The abscissas are the ranges in air of the a particles when they 

 enter the metal sheets ; the ordinates the air- equivalents of the metal sheets. 

 The curve for BSn has the ordinates from 1*718 to 1 '80 as indicated on 

 right-hand side of the figure instead of 1*118 to 1*20 as shown on left-hand 

 side. 



