58 NOTE ON REGELATION. 
united; and, assuming a new position, would, in a second or less, 
again become rigid, and remain inflexibly conjoined as before. 
By managing the continuous motion of one piece of ice, it could 
be kept associated with the other by a flexible point of attachment 
for any length of time, could be placed in various angular positions 
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 mto 
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- 
