Taylor — Retardation of Alpha Bays by Metals. 361 



Table II. 



Eange 



















in cms. c 



f 

















entering 

















a-par- 

 ticle 



A Al 



B Al 



C Al 



DAI 



A Au 



B Au 



C Au 



D Au 



5-7 



0-597 



1-209 



1-803 



2-672 



0-719 



0-980 



1-375 



1-900 



5'3 



0-597 



1-206 



1-792 



2-659 



0-706 



0-966 



1-352 



1-869 



4-9 



0-597 



1-202 



1-781 



2'644 



0-693 



0-947 



1-328 



1-837 



4-5 



0-597 



1-198 



1-769 



2-628 



0-680 



0-929 



1-303 



1-802 



4-1 



0-597 



1-193 



1-757 



2608 



0-668 



0-910 



1-276 



1-763 



3-7 



0-597 



1-187 



1-742 



2-582 



0-657 



0-889 



1-248 



1-720 



3-3 



0-596 



1-178 



1-724 





0644 



0866 



1-214 



1-659 



2 9 



0*595 



1-168 



1-705 





0-630 



0-837 



1-178 



1-598 



2-5 



0-592 



1-152 







0-616 



0-805 



1-127 





2-1 



0-584 



1-131 







0-600 



0-757 







1-7 



0-570 









0-582 









1-3 



0-555 

















Range 

 in cms. of 

















entering 

















a-par- 



ticle 



ASn 



B Sn 



APb 



BPb 



CPb 



Paper 



Celloidin 



5-7 



1-011 



1-995 



1-104 



1-396 



2-325 



1-020 



0-520 





5-3 



1-002 



1-980 



1-085 



1-371 



2-596 





a 





4-9 



0-993 



1-960 



1-064 



1-343 



2-260 





a 





4-5 



0-984 



1-938 



1-042 



1-320 



2-220 





a 





4-1 



0-971 



1-914 



1-020 



1-289 



2-180 





a 





3-7 



0*957 



1-884 



0-999 



1-263 



2-124 





tt 





3*3 



0-941 



1-845 



0-977 



1-232 



2-046 





(( 





2-9 



0-923 



1-795 



0-950 



1-200 







a 





2-5 



0-902 





0-923 



1-163 







u 





2*1 



0-882 





0-888 









a 





1-7 



0-853 













tc 





1-3 















a 





The height of the plug containing the radium was 0-9 cm above 

 the radium. Therefore the maximum available range of the 

 alpha particles entering the sheet is 5*70. The values of the 

 air-equivalents for each of the metal sheets in Table II repre- 

 sent the average results obtained from a series of from six to 

 ten separate determinations, the details of which have been 

 omitted for the sake of brevity. 



Experiments were also made with sheets of paper and cel- 

 loidin." Two sheets of paper of about 1 and 2 cms air-equivalent 

 respectively, and three sheets of celloidin of air-equivalents of 

 the order of 0'5, 1*0 and 2'0 cms respectively were used. For 

 these sheets of paper and celloidin, the ionization did not 

 increase as the sheets were moved away from the radium, but 



* Celloidin is a specially pure preparation of collodion. 



