130 
POPULAR SCIENCE REVIEW. 
To begin with, the tin bottle was placed in the position G 
and filled with a freezing mixture of salt and ice. Some boiled 
water was then passed up the tube DE, sufficient to form a 
column at M about two inches deep. The thermometer H had 
been previously arranged, so that its bulb might be one or two 
inches above the surface of the water M. The bottle A was 
next surrounded by a good quantity of a freezing mixture of 
salt and ice, in order that any vapour given off from the water 
at M might be condensed in A as fast as it was formed, and 
thus the internal pressure might never be more than about TO 
to 1*5 millims. When A had been sufficiently cooled, which 
required about fifteen minutes, the tin vessel G was slid down 
the tube DE, and its freezing mixture removed. The water at 
M had then solidified to a mass of ice, which on heating with 
the flame of a Bunsen’s burner melted either wholly or partially, 
and the liquid formed began at once to boil. The fusion com- 
menced first at the bottom of the column of ice, whereas the 
upper part fused only with difficulty, and required rather a 
strong heat. The fusion in this case was probably due to the 
steam evolved from the lower portions of the ice column being 
imprisoned and unable to escape, and hence producing pressure 
sufficient to cause fusion. 
When the greater part of the ice had been melted the tube 
was tightly clasped by the hand, the heat of which was suffi- 
cient to produce a somewhat violent ebullition. The liquid in 
boiling splashed up the side of the tube and on to the bulb of 
the thermometer, where it froze into a solid mass, as repre- 
sented in fig 2. By this means the ice was obtained in mode- 
rately thin layers. The tube at the points indicated by the 
arrows was then strongly heated by the flame of a Bunsen’s 
burner, with the following results : — 
The ice attached to the sides of the tube at first slightly 
fused, because the steam evolved from the surface of the ice- 
next the glass being imprisoned between the latter and the 
overlying strata of ice, could not escape, and hence produced 
pressure sufficient to cause fusion, but as soon as a vent-hole 
had been made fusion ceased, and the whole remained in 
a solid state, and neither the ice on the sides of the tube nor 
that on the bulb of the thermometer could be melted, however 
great the heat applied, the ice merely volatilizing without 
previous melting. The thermometer rose to temperatures vary- 
ing between 120° and 180° in different experiments, when the 
ice had either wholly volatilized or had become detached from 
the bulb of the thermometer. The ice attached to the latter 
did not partially fuse at the commencement of the heating, 
because, the heat reaching the outer surface of the ice first, 
evaporation could take place from a free surface, and the vapour 
