.1881.] Existence of Ice and other Bodies in the Solid State. 287 



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 not become imprisoned, as was the case with the ice 

 attached to the sides of the tube. 



Fig. 2. 



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, notwithstanding that the portion of the glass in 

 contact with it was so hot that it could not be touched without burning 

 the hand. 



The chief conditions necessary for success appear to be — (1) That 

 the condenser (A, fig. 1) is sufficiently large to maintain 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 



