1858.] On Regelation. 381 



deposition of solid particles upon them from the surrounding 

 fluid, that would not have been so deposited without the 

 presence of the previous solid portions; a fact sufficiently 

 proved by the growth of fine crystals of ice in ice-cold water. 

 This effect was admirably shown in Mr. Harrison's freezing 

 apparatus, where beautiful thin crystals of ice, six, eight, and 

 ten inches long, would form in the surrounding fluid ; and 

 these crystals, which could not be colder than the surrounding 

 fluid, exhibited the phenomena of regelation when purposely 

 brought in contact with each other. 



The next point may be considered as an assumption : it is 

 that many particles in a given state exert a greater sum of their 

 peculiar cohesive force upon a given particle of the like substance 

 in another state than few can do ; and that as a consequence 

 a water particle with ice on one side and water on the other, 

 is not so apt to become solid as with ice on both sides ; also 

 that a particle of ice at the surface of a mass in water is not 

 so apt to remain ice as when, being within the mass, there is 

 ice on all sides, temperature remaining the same. If that be 

 admitted, then regelation is sufficiently accounted for. Dif- 

 ference of temperature above or below that of the changing 

 points of water is not alone sufficient to cause change of state, 

 the change being independent of temperature throughout a large 

 range. At such times the particles appear to be governed by 

 cohesion. Cohesion resolves itself into the force exerted on 

 one particle by its neighbours, and this force seems to me to be 

 sufficient, under the circumstances, to account for regelation. 



Supposing this to be the true view of the state of things, 

 then a particle of ice within ice can exist at a temperature 

 higher than a like particle of ice on its surface in contact with 

 water ; and though it does not appear at present how a higher 

 temperature could be communicated to the interior of a mass 

 of freezing ice than that existing over its surface, still there 

 may be principles of action in radiation, and even in conduction 

 and liquefaction, producing that effect. Assuming, however, 

 that a piece of freezing ice is in such a state, then, if it were 

 to be pulverized, it ought to produce a mixed mass of ice and 

 water colder than the ice was before. Such seems to be the 

 result in one of Prof. Forbes's experiments, in which ice rapidly 

 pounded showed a temperature of 0*3 Falir, below the tern- 



