340 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
to remove all j)0ssibility of leakage around the stopper A, the flame of a 
Bunsen’s burner is applied to the sealing-wax until it is sufficiently 
softened for the pressure of the atmosphere to force it into any crevice 
that it has not reached. When the column of mercury in D becomes 
stationary, admit hydrogen by means of I, until the vacuum in A is 
Fig. 31. 
destroyed. Close I and Id and open L until exhaustion is complete ; 
close L and open H and I successively. The alternate exhaustion and 
tilling are repeated until there is no possibility of any air remaining in 
A, when the tubes a and a! are drawn apart and sealed in the flame. In 
order that the pressure within A may be only very slightly different 
from that of the atmosphere, H is not opened after the last exhaustion. 
