408 Royal Society :— 



ternally to simply .atmospheric pressure : — and though I shall also, in 

 what follows, point out some additional conditions, almost necessarily 

 present in the experiment, which, under my general view of the 

 plasticity of ice, would act in conjunction with those already adduced, 

 and would increase the rapidity of the union. 



Professor Faraday, holding it in view to remove the ground on 

 which my explanation of Principal Forbes's experiment was founded, 

 has contrived and carried out a set of new and very beautiful experi- 

 ments from which the capillary action referred to has been com- 

 pletely eliminated, and he lias still found the union of the ice to 

 occur, and to increase with time, and has met with a curious addi- 

 tional phenomenon of "flexible adhesion"*. In these experiments, 

 when two pieces of ice, rounded so as to be convex at their points 

 where mutual contact is to be allowed, are placed in water, and are 

 either anchored so as to be wholly under water, or are placed floating 

 when so formed that they can touch one another only under water, 

 and that, at the water surface, there shall be a wide space between 

 them so that there shall be no capillary action drawing them to- 

 gether, he showed that the pieces of ice, in either of these cases, if 

 brought gently into contact, will adhere together ; unless indeed the 

 movement bringing them into contact be so directed as to introduce 

 forces capable of tearing them apart again by obliquity of action, by 

 agitation of the water, or by other disturbances. He showed also 

 that, if when the two pieces of ice have become attached at their 

 point of contact, a slight force, such as may be given by one or two 

 feathers, be applied, tending to separate them, at one side of their 

 point of contact, they will roll round one another with a seemingly 

 flexible adhesion ; or that, if the point of a floating wedge-shaped 

 piece of ice is brought under water against the side of another float- 

 ing piece, it will stick to that piece like a leech. He showed that if 

 the pieces be allowed to remain for a few moments in contact, their 

 adhesion will become rigid, so that on a force being applied sufficient 

 to break through the joint, the rupture will occur with a crackling 

 noise, though the pieces may still continue to hold together, rolling 

 on one another with the flexible adhesion. He made some other ex- 

 periments nearly the same as these, but in which he showed the 

 flexible and rigid adhesion to occur while there is constantly a decided 

 tensile force applied externally tending to pull the pieces asunder 

 instead of any external force tending to press them together. He 

 thinks that the phenomena of flexible and rigid adhesion " under 

 tension" go towards showing that pressure is not necessary to " re- 

 gelation." He then gives his own idea of the flexible and rigid 

 adhesion in the following words : — "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 dispersed, more particles will solidify, and 

 ultimately enough to form a fixed and rigid junction, which will 

 * Phil. Mag. S. 4. vol. xxi. p. 146. 



