Substance emitted from Thorium Compounds. 



Table IV. 



Length of cylinder = 30 cms. 



Internal diameter outer cylinder = 5*5 cms. 

 External „ inner „ = *8 cm. 



100 volts between cylinders. 



11 



Time in Seconds. 



1 

 Current in Scale-divisions 

 per second. 







2-4 



75 



33 



23 



65 



40 



100 



53 



12-5 



6-7 



13-8 



96 



17-1 



12 5 



194 



18-4 



227 



244 



253 



30 4 



25-6 



48-4 



25-6 



The results are expressed in fig. 2, curve B, where the 

 ordinate represents current and the abscissa time. It will be 

 observed that the curve of rise of the current is similar in 

 form to the rise of an electric current in a circuit of constant 

 inductance. The current reaches half its value about one minute 

 after the current of air has stopped,— a result which agrees 

 with the equation given, for e~ xt = ^ when £ = 60 seconds (see 

 Table IV.). At the instant of stopping the current of air 

 the current has a definite value, since most of the ions given 

 oft' by the emanation, before it is blown out of the cylinders, 

 reach the electrodes. 



When the source of the emanation is removed, q = Q, and 

 the decay of the number of ions produced by the emanation is 

 given by the equation 



tin 



If w=N when £ = 0, it is easily seen that 



N ' 



