Prof. Faraday on Regelation. 151 
between the flexible and rigid adhesion may be examined very well in 
air, _ For this purpose, two of the bars of ice before spoken of, may 
be hung up horizontally by threads, which may be adjusted to give 
by torsion any separating force desired ; and when the ends of these 
bars are brought together, the adhesion of the ice, and the ability of 
placing these bars at any angle, and causing them to preserve 
that angle by the rigid adhesion due to regelation, will be rendered 
evident ; and though the flexible adhesion of the ice cannot in this 
way be examined alone, because of the capillary attraction due to the 
film of water on the ice, yet that is easily obviated by plunging the 
pieces into a dish of water at common temperatures, so that they are 
entirely under the surface, and repeating the observations there. All 
the important points regarding the flexible and rigid junction of ice 
due to regelation, can in this way be readily investigated. 
It will be understood that, in observing the flexible and rigid state 
of union, convex surfaces of contact are necessary, so that the contact 
may be only at one point. If there be several places of contact, 
apparent rigidity is given to the united mass, though each of the 
places of contact might be in a flexible and, so to say, adhesive con- 
dition. It is not at all difficult to arrange a convex surface so that, 
bearing at two places only on the sides of a depression, it should 
form a flexible joint in one direction, and a rigid attachment in a 
direction transverse to the former. 
it might seem at first sight as if the flexible adhesion of the ice 
gave us a point to start from in the further investigation of the prin- 
ciple of pressure. Ifthe application of pressure causes ice to freeze 
together, the application of tension might be expected to produce the 
contrary effect, and so cause liquidity and separation at the flexible 
jomt. This, however, does not necessarily follow ; nor do I intend to 
consider what might be supposed to take place whilst theoretically 
contemplating that case. I think the changes of temperature and 
pressure are too infinitesimal to go for anything; and in illustration 
of this, will deseribe the following experiment. Wool is known to 
adhere to ice in the manner, as I believe, of regelation. Some wool- 
len thread was boiled in distilled water, so as thoroughly to wet it. 
Some clean ice was broken up small and mixed with water, so as to 
produce a soft mass, and, being put into a glass jar clothed in flan-, 
nel that it might keep for some hours, had a linear depression made 
in the surface, so as to form alittle ice-ditch filled with water ; in this 
depression some filaments of the wetted wool were placed, which, 
sinking to the bottom, rested on the ice only with the weight which 
they would have being immersed in water; yet in the course of 
two hours these filaments were frozen to the ice. In another case, a 
small loose ball of the same boiled wool, about half an inch in 
diameter, was put on to a clean piece of ice ; that into a glass basin; 
and the whole wrapped up in flannel and left for twelve hours. At 
the end of that time it was found that thawing had been going on, 
and that the wool had melted a hole in the ice, by the heat conducted 
through it to the ice from the air. The hole was filled with the 
water and wool, but at the bottom some fibres of the wool were 
frozen to the ice. : 
