Mr. Norman Campbell on Delta Rays. 



289 



generally greater than the difference between "V=0" and 

 " V = (magnet)/' but there is a certain parallelism between 

 the two differences : when one is large, so is the other. The 

 general nature of the effect is such as would be expected ; 

 the discrepancy in magnitude will be noted in a subsequent 

 discussion : it is in part due, no doubt, to the uncertainty 

 about the true zero noted already. It may be noted that if 

 a correction were introduced for the decay of the polonium 

 the charge on the alpha rays would decrease continuously 

 with an increase in the thickness of the absorbing layer. 



13. Similar experiments, though less exhaustive, have 

 been performed on copper, silver, and gold. In these cases 

 A was covered by a plate of the metal impenetrable to alpha 

 rays, while one thin leaf (in the case of silver also two leaves) 

 were placed over B. The thickness (surface density) of the 

 leaves was approximately as follows : — 



Cu 0*0003 gr./cm. 2 : Ag O'OOl gr./cm. 2 : An 0'0002 gr./cm. 2 



The results are given in Tables III., IV., V., which should 

 be comprehensible without further explanation. A word 



Table III. 

 Gold. 



Table IV. 

 Copper. 





+ 



- 



Sura. 



v— 



0-138 



0-138 





Y = (magnet). 0-152 



0-152 | 



V = 40 0-569 



1 



0-284 



0853 



V-£ 



0-216 



0-199 

 •348 

 552 

 •659 

 •735 

 •848 

 •905 

 •955 



1-000 



0-208 

 •355 

 •543 l 

 •662 

 •736 

 •827 !| 

 •900 

 •962 



1-000 ; 



1 



2 



•362 

 ■533 

 •663 

 •735 

 •805 

 •893 

 •966 

 1-000 



3 



4 



6 



8 



12 



40 





Ratio +/- 0-S4. 



+ |-| Sura. 



V = 



0123 



i 



0-123 



V=0 (magnet) 



0135 



0135 



V = 40 



0381 0-452 



1 1 



0833 



v=* 



1 







3 



4 



0266 

 •420 

 •617 



1 -748 

 •817 

 •898 



; -940 



, 1-000 



1 



0-266 

 •410 

 •608 

 •715 

 •812 

 •889 

 •934 



1000 



0-266 

 0-415 

 0-613 

 0-735 

 0814 

 0-893 

 0-936 

 1000 



6 



8 



40 



Phil Mag. S. 6. Vol. 22. No. 128. Aug. 1911. 



U 



