170 
rate nearly 30 inches down the tube, 
and then the appearance of the upper 
portion falling was very singular. The 
upper portion of the column remained 
intact, and a stream of mercury fell 
from its under surface, as shown in 
Fig. 4, breaking up into globules as 
it came into contact with the lower 
portion with a loud rattling noise. I 
was unable to get the column in the 
tube thus filled to maintain itself for 
more than 20 or 30 seconds, which 
failure was clearly due to the presence 
of air, for after the mercury had fallen 
a small quantity of air was always 
found to collect above it. Sometimes 
when, on inclining the tube, the liquid 
again reached the top, the bubble 
which remained was so small as to 
be scarcely visible, although subject 
to no pressure other than the surface 
tension, but its presence always became apparent in- 
stantly on erecting the tube. In no case was it possible, 
after the mercury had once fallen, to get it to remain up to, 
any considerable height above that due to the pressure of 
the atmosphere until the bubble of air collected had been 
allowed to pass out. 
The tube was then again emptied, washed, and filled with 
glycerine. This behaved much in the same manner as the 
water, but the difficulty of getting rid of the air was greater. 
Similar results were obtained when very dilute ammonia 
liquid was tried. 
The tube was then again carefully washed, first with 
water and then several times with concentrated sulphuric 
acid. The mercury was subjected to nitric acid, washed and 
dried, and then filtered into a bottle of sulphuric acid, from 
