446 



point of contact, then I think that the union is broken up among the 

 particles on the opening side of the angle, whilst the particles on the 

 closing side come within the effectual regelation distance ; regelation 

 ensues there and the adhesion is maintained, though in an apparently 

 flexible state. The flexibility appears to me to be due to a series of 

 ruptures on one side of the centre of contact, and of adhesion on the 

 other, the regelation, which is dependent on the vicinity of the ice 

 surfaces, being transferred as the place of efficient vicinity is changed. 

 That the substance we are considering is as brittle as ice, does not 

 make any difficulty to me in respect of the flexible adhesion ; for if 

 we suppose that the point of contact exists only at one particle, still 

 the angular motion at that point must bring a second particle into 

 contact (to suffer regelation) before separation could occur at the 

 first ; or if, as seems proved by the supervention of the rigid adhesion 

 upon the flexible state, many particles are concerned at once, it is not 

 possible that all these should be broken through by a force applied 

 on one side of the place of adhesion, before particles on the opposite 

 side should have the opportunity of regelation, and so of continuing 

 the adhesion. 



It is not necessary for the observation of these phenomena that a 

 carefully-arranged water-vessel should be employed. The difference 

 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, 



