[BOYLE] TEMPERATURE AND VELOCITY OF GAS CURRENT 91 
Let WM = the number of free emanation atoms given off by the 
thorium hydroxide per sec., 
q = 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 ¢ ¢.c. of air entering the testing vessel are associated 
nh T 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,, 

vA oi 
then idles eae te ‘ 
q 
Let V be the total free volume of the conducting tubes between 
À : \ L Ve 
the thorium hydroxide tube and the testing vessel, then 7 = — | 
q 
r AV 
71 Tr ho 
and No = i 
. 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 by the figure 3. —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, 
AZ 
n-= n, e 2 
The total number of emanation atoms in the element dw 
= n dw -yd 
UNS et OID 
Ww a 
bi) Bie) tale do 
where W is the whole volume of th> testing vessel. 
