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to it, could be made (by retaining it quiescent for a moment) to 

 assume and hold permanently any of these positions when the ex- 

 ternal force was removed., could be changed from that position into 

 a new one, and, within certain limits, could be made to possess at 

 pleasure, and for any length of time, either a flexible or a rigid attach- 

 ment to its associated block of ice. 



So, regelation includes a flexible adhesion of the particles of ice, 

 and also a rigid adhesion. The transition between these two states 

 takes place when there is no external force like pressure tending to 

 bring the particles of ice together, but, on the contrary, a force of 

 torsion is tending to separate them ; and, if respect be had to the 

 mere point of contact on the two rounded surfaces where the flexible 

 adhesion is exercised, the force which tends to separate them may 

 be esteemed very great. The act of regelation cannot be considered 

 as complete until the junction has become rigid ; and therefore I 

 think that the necessity of pressure for it is altogether excluded. 

 No external pressure can remain (under the circumstances) after the 

 first rigid contact is broken. All the forces which remain tend to 

 separate the pieces of ice ; yet the first flexible adhesions and all the 

 successive rigid adhesions which are made to occur, are as much effects 

 of regelation as those which occur under the greatest pressure. 



The phenomenon of flexible adhesion under tension looks very 

 much like sticking and tenacity ; and I think it probable that Pro- 

 fessor Forbes will see in it evidence of the truth of his view. I 

 cannot, however, consider the fact as bearing such an interpretation ; 

 because I think it impossible to keep a mixture of snow and water 

 for hours and days together without the temperature of the mixed 

 mass becoming uniform ; which uniformity would be fatal to the 

 explanation. My idea of the flexible and rigid adhesion is this : 

 Two convex surfaces of ice come together ; the particles of water 

 nearest to the place of contact, and therefore within the efficient sphere 

 of action of those particles of ice which are on both sides of them, 

 solidify ; if the condition of things be left for a moment, that the 

 heat evolved by the solidification may be conducted away and dis- 

 persed, more particles will solidify, and ultimately enough to form 

 a fixed and rigid junction, which will remain until a force sufficiently 

 great to break through it is applied. But if the direction of the 

 force resorted to can be relieved by any hinge-like motion at the 



