﻿Mr. Norman Campbell on Delta Rays. 



49 



was covered successively with aluminium, copper, silver, and 

 gold. The results are plotted in fig. 2 (p. 50), where the 

 ordinates now represent the absolute values of the current, 

 expressed in the units described in the previous paper, and 

 not the ratios of the current to the maximum current. In 

 Table II. the results are given in a form similar to that of 

 Table I., except that the " sum " column is omitted as 

 having no significance when the electrodes are of different 

 materials. 



Table II. 





Aluminium. 



Copper. 



Silver. 



Gold. 





+ 



+ - 



+ 



+ - 



v^o 



-•009 



-•064 



-•029 



-•040 



V=0 (magnet)... 



-•065 



-•056 



-•055 



-•0 F 6 



y=40 



0-313 



0-184 



0-360 



0-086 



0-321 



0-093 



0-328 



0-103 





Y-h 



•144 

 •252 

 •441 

 •559 

 •649 

 •757 

 •824 

 1-000 



•321 



•582 

 •788 

 •881 

 •918 

 •973 

 •994 

 1-000 



•127 



•259 

 •449 

 •562 

 •659 

 •754 

 •838 

 1000 



•296 

 •478 

 •675 

 •768 

 •861 

 •909 

 •949 

 1000 



•137 

 •271 

 •458 

 •576 

 •654 

 •766 

 •829 

 1-000 



•269 

 •484 

 •645 

 •763 

 •828 

 •914 

 •935 

 1-000 



•147 

 •269 

 •452 



•569 

 •654 

 •762 

 •829 



1-000 



1 



•285 

 •466 

 •650 

 •779 

 •839 

 •907 

 •942 

 1-000 



1 



2 



3 



4 



6. 



8 



40 



It may be noted in passing that additional evidence was 

 obtained for the conclusion, given in the previous paper, 

 that the quality of the delta rays excited in a substance is 

 independent of the speed of the alpha rays exciting them. 

 For most of the observations given in Table II. were repeated 

 with the polonium plate covered by a layer of aluminium 

 foil equivalent in its stopping power to about 3 cm. of air. 

 The presence of the foil increased all the values given in the 

 table below the thick line by about 50 percent. — the increase 

 is doubtless due to the greater ionizing power of the alpha 

 ray towards the end of its range- — but it did not change the 

 ratio of those values to any perceptible extent. The form 



Phil Mag. K y . 6. Vol. 23. Efo. 133. Jan. 1912. E 



