Mineral Springs of Colorado. 



623 



scope. The problem was solved by constructing a num- 

 ber of ionization chambers to which could be attached in 

 turn the same electroscope head and leaf. The dimen- 

 sions, constants, and characteristics of these electro- 

 scopes have been fully discussed in a previous paper. 2 



Fig. 1, 



effidp: 



The essential features are shown in fig. 1. I is an air- 

 tight cylindrical brass ionization chamber having stop 

 cocks V near the top and bottom. Altogether four such 

 chambers were used, all taking the same electroscope 

 head but each having its own electrode E. 



The head screws on at T and is made air-tight by the 

 rubber gasket r. S is an insulation made of banker's 

 specie sealing wax. Through this passes a brass rod 



8 This Journal, 44, 225, 1917. 



