380 Mr. R. W. Boyle on the Absorption of 



all removed by the air-current. In consequence, there will 

 he the same number of emanation atoms leaving the thorium- 

 tube per second for any speed o£ the air-current. 



The ionization current in the testing vessel is proportional 

 to the number of emanation atoms breaking up per second in 

 the testing-vessel ; and this number is X times the number 

 of emanation atoms present, \ being the coefficient of decay 

 of the emanation. 



Let N = the number of free emanation atoms given off by 

 the thorium hydroxide per sec, 

 (7 = the flow of the air-current in c.c. per sec, 

 T = the time for the air to pass from the thorium 

 hydroxide to the testing-vessel. 

 Then, with g c.c of air entering the testing-vessel are 

 associated N<T AT atoms of emanation. If we denote the 

 number of emanation atoms per c.c. of air at the entrance 

 of the testing-vessel by n , then 



«o = ■ 



9 



Let Y be the total free volume of the conducting tubes 



between the thorium hydroxide tube and the testing- vessel ; 



then v 



T = --, 



9 



and .* 



q q 



To obtain the total number of emanation atoms, P, present 

 in the testing-vessel, consider an element of volume dw, with 

 a volume w between the entrance and the element, as shown 



10 

 by fig. 4. — is the time for the air to traverse the volume w, 



and therefore, if n=the number of emanation atoms per c.c. 

 of air within the element, 



n = n e q . 

 The total number of emanation atoms in the element dw 

 = ndw 



Azy 



= n e q die ; 



W _\io 



P = n e -j~aw, 





 where W is the whole volume of the testing-vessel. 



