Different Types of Beta Rays. 



139 



the chamber ; and the values of the saturation-currents are 

 given in columns I., II., III., IV., V., and VI. of Table IX. 



Table IX. 

 Ionization by /3 reflected Secondary Rays from Lead-foil. 





Saturation Current (arbitrary scale), with 







different thicknesses of Lead-foil. 





Current 

 in magnet 

















! 







(amperes). 



I. 



II. 



III. 



IV. 



V. 



VI. 





mm. 



mm. 



mm. 



mm. 



mm. 



mm. 





o-o 



0066 

 13150 



0-093 

 1337-0 



0-116 

 13490 



0241 

 13490 



0-964 

 1340-0 



00 



11610 



0-8 



799-0 





809-8 



... 



818-5 



801-3 



2-5 



146-0 





147-8 





139-8 



145-0 



4-5 



64-9 





59-5 





65-3 



63-8 



6-5 



58-9 



• . 



54-7 



... 



54-2 



55-5 



100 



57-8 





56-3 



58-3 



56-1 





150 



58-9 



57-8 



586 



58-0 





566 



220 



57-8 



56-9 



57-2 



56-6 



56-9 



569 



28-0 



56-9 



56-1 



56-3 



560 



55-3 



55-8 



From these it will be seen that with the lead reflectors of 

 different thicknesses, the saturation currents were practically 

 the same when magnetic fields of sufficient strength to 

 deflect all the ft rays were applied. In order to ascertain 

 the maximum ionization for the various lead reflectors due 

 to the* /3 ray effect, the mean of the readings obtained with 

 the high fields was taken as representing the conductivity 

 due to y radiations, that due to the secondary radiations 

 excited by these in the reflectors, and also that due to the 

 so-called natural ionization. This mean was subtracted 

 from the maximum ionization obtained with each of the 

 reflectors before the application of a magnetic field, and 

 the differences, which are recorded in column IV. of Table X. 



Table X. 



Thickness 



of lead 



over bottom 



of chamber. 



Max. /34-j3 secondary 

 4- y -f y secon dary -f 

 natural ionization. 



y + y secondary + 

 natural ionization. 



Max. /3 +/3 

 secondary 

 ionization. 



mm. 



o-o 



0066 

 0093 

 0-116 

 0-241 

 0-964 



1161 

 1315 

 1337 

 1349 

 1349 

 1340 



57-8 

 56-9 

 56-7 

 57-3 

 55-6 

 56-2 



11032 

 1258- 1 

 1280-3 

 1291-7 

 1293-4 

 1283-8 



