EXISTENCE OF ICE AT HIGH TEMPERATURES. 
131 
not become imprisoned, as was tbe case with the ice attached 
to the sides of the tube. 
These experiments were repeated many times, and always 
with the same result, except in one case in which the heat 
applied had been very strong indeed, and the ice attached to 
the sides of the tube fused completely. On removing the 
lamp, however, for a few seconds the water froze again, not- 
withstanding that the portion of the glass in contact with 
it was so hot that it could not be touched without burning the 
hand. 
Fig. 2. 
The chief conditions necessary for success appear to be — - 
(1) That the condenser (A, fig. 1) is sufficiently large to main- 
tain a good vacuum. In the present case the capacity was 
about three quarters of a litre ; (2) That the ice is not in too 
great mass, but arranged in thin layers. Further, in the case 
where the heat is applied to the under surface of the layers of 
ice, the latter must be sufficiently thin to allow of a vent-hole 
being formed for the escape of the steam coming from below, 
