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of ice, having their corresponding surfaces ground tolerably flat, were 

 suspended in an inhabited room upon a horizontal glass rod passing 

 through two holes in the plates of ice, so that the plane of the plates 

 was vertical. Contact of the even surfaces was obtained by means of 

 two very weak pieces of watch spring. In an hour and a half the 

 cohesion was so complete, that, when violently broken in pieces, many 

 portions of the plates (which had each a surface of twenty or more 

 square inches) continued united. In fact it appeared as complete as 

 in another experiment where similar surfaces were pressed together 

 by weights." He concludes that the effect of pressure in assisting 

 ' regelation' is principally or solely due to the larger surfaces of con- 

 tact obtained by the moulding of the surfaces to one another. 



I have myself repeated this experiment, and have found the re- 

 sults just described to be fully verified. It was not even necessary to 

 apply the weak pieces of watch-spring, as I found that the pieces of 

 ice, on being merely suspended on the glass rod in contact, would 

 unite themselves strongly in a few hours. Now this fact I explain by 

 the capillary forces of the film of interposed water as follows: Firstly, 

 the film of water between the two slabs being held up against gravity 

 by the capillary tension, or contractile force, of its free upper surface, 

 and being distended besides, against the atmospheric pressure, by the 

 same contractile force of its free surface round its whole perimeter, 

 except for a very small space at bottom, from which water trickles 

 away, or is on the point of trickling away exists under a pressure 

 which, though increasing from above downwards, is everywhere, ex- 

 cept at that little space at bottom, less than the atmospheric pres- 

 sure. Hence the two slabs are urged towards one another by the ex- 

 cess of the external atmospheric pressure above the internal water 

 pressure, and are thus pressed against one another at their places of 

 contact by a force quite notable in its amount. If, for instance, be- 

 tween the two slabs there be a film of water of such size and form as 

 might be represented by a film one inch square, with its upper and 

 lower edges horizontal, and with water trickling from its lower edge, 

 it is easy to show that the slabs will be pressed together by a force 

 equal to the weight of half a cubic inch of water. But so small a film 

 as this would form itself even if the two surfaces of the ice were only 

 very imperfectly fitted to one another. If, again, by better fitting, a 

 film be produced of such size and form as may be represented by a 



