Mr. J. Gill on Beg elation. 123 



quantity corresponding to the lowering of its freezing-point by 

 the pressure. But the freezing-point of the uncompressed water 

 is not lowered. [This is said of the glacier-water supposed to 

 be free to escape through fissures ; but it applies here, as the 

 cause assigned to the pressure on the ice is the shrinking of the 

 intervening water.] Here, then, we have ice colder than 0° C. 

 in contact with water at 0° C. [the water of liquefaction]. The 

 consequence is, that round the place of pressure the water will 

 freeze and form new ice, while, on the other hand, a portion of 

 the compressed ice continues to be melted." The water of lique- 

 faction would in the first place form zones round the solid points 

 of contact, displacing laterally the surrounding water of the liquid 

 films, while the particles of ice simultaneously forming round 

 the solid prominences would act as wedges or props to compen- 

 sate the lowering of the points by liquefaction, and so maintain 

 the original distance of the surfaces (approximately), and con- 

 sequently the partial vacuum originally formed by the shrinking 

 of the liquid films. Meanwhile the heat thrown out by the 

 forming ice, and the heat of the enclosed films which are at a 

 temperature above that of the surrounding ice, would pass into 

 the solid mass, — perhaps quite through it without causing lique- 

 faction, according to TyndalFs idea ; but at least, in the case 

 under consideration, the heat should naturally pass from the 

 water into the ice, because the temperature of the water should 

 be sensibly higher. 



When fragments of ice are floating in warm water with the 

 appressed surfaces submerged, we must suppose that before con- 

 tact took place the surfaces were melting and sending off liquid 

 particles at or very little above 32° at the moment of their sepa- 

 ration from the solid mass, which particles would be floating 

 away with a certain amount of vis viva in their motion of trans- 

 lation. On the contact of the two pieces of ice this motion would 

 be stopped and changed into heat, which would act locally on the 

 liquid film formed by the arrested particles themselves, convert- 

 ing their previous motion of translation into heat-motion ; and 

 hence the shrinking of the liquid films, and consequent pressure 

 on the solid points of contact required to explain the fact of 

 regelation. 



Palermo, December 24, 1865. 



