166 . Prof. Faraday on Regelation, 



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 govei-ned by 

 cohesion. Cohesion resolves itself into the force exerted on one 

 particle by its neighbours ; and this force seems to me to be suf- 

 ficient, 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 Fahr. below the tem- 

 perature of snow in a thawing state. The experiment, however, 

 would require much consideration in every point of view, and 

 much care before it could be considered as telling anything 

 beyond the temperature of ice-cold water. 



On the other hand, if a spherical cup of ice could be pre- 

 pared containing water within, to which no heat could pass 

 except by conduction through the ice itself, that water ought 

 to be a little colder than the ice cup around it : also if a 

 mixture of snow and water were pressed together, the tempe- 

 rature should rise whenever regelation occurred, being an effect 

 in the contrary direction to that which Prof. J. Thomson con- 

 templates ; and such a mixture, as a whole, ought to be warmer 

 than the water in the ice sphere mentioned above. No doubt 

 nice experiment will hereafter enable us to criticise such imagi- 

 nary results as these, and, separating the true from the untrue, 

 will establish the correct theory of regelation. 



On the Conservation of Force. 

 During the year that has passed since the publication of cer- 

 tain views regarding gravitation, &c., I have come to the know- 



