E. W. Morley—Oxygen in the Aw. 171 
tube; these last meet the glass tubes and are connected wit 
them by short tubes of patent black rubber containing no free 
sulphur. The connectors are tied so as to endure the pressure 
of mercury having a head of several feet, and are surrounded 
with mercury so as to be absolutely air-tight. The plug of 
the iron stop-cock is also so surrounded with mercury that the. 
entrance of air is absolutely impossible, and the same precau- 
tion was taken at the junction of the two small iron tubes with 
the horizontal tube. The cast iron of this tube and stop-cock 
is well japanned, and no leakage through its pores has 
occurred. 
Such an adjustment can be accurately made by admitting 
fits 
the pressure tube and the rest of the apparatus. The mercury 
in the pressure tube is, by the use of this valve, always kept 
at such a height shinit any possible leakage 1S that of mercury 
Outward, and not of air inward. 
