442 



atmosphere, only. It seemed to me that experiment might be so 

 applied as to advance the investigation of this beautiful point in 

 molecular philosophy to a further degree than has yet been done ; 

 even to the extent of exhausting the power of some of the principles 

 assumed in one or more of the three views adopted, and so render 

 our knowledge a little more denned and exact than it is at present. 



In order to exclude all pressure of the particles of ice on each 

 other due to capillary attraction or the atmosphere, I prepared to 

 experiment altogether under water ; and for this purpose arranged a 

 bath of that fluid at 32 F. A pail, surrounded by dry flannel, 

 was placed in a box ; a glass jar, 10 inches deep and 7 inches wide, 

 was placed on a low tripod in the pail ; broken ice was packed be- 

 tween the jar and the pail ; the jar was filled with ice-cold water to 

 within an inch of the top ; a glass dish filled with ice was employed 

 as a cover to it, and the whole enveloped with dry flannel. In this 

 way the central jar, with its contents, could be retained at the un- 

 changing temperature of 32 F. for a week or more ; for a small piece 

 of ice floating in it for that time was not entirely melted away. All 

 that was required to keep the arrangement at the fixed temperature, 

 was to renew the packing ice in the pail from time to time, and also 

 that in the basin cover. A very slow thawing process was going on 

 in the jar the whole time, as was evident by the state of the indi- 

 cating piece of ice there present. 



Pieces of good Wenham-lake ice were prepared, some being blocks 

 three inches square, and nearly an inch thick, others square prisms 

 four or five inches long : the blocks had each a hole made through 

 them with a hot wire near one corner ; woollen thread passed through 

 these holes formed loops, which being attached to pieces of lead, 

 enabled me to sink the ice entirely under the surface of the ice-cold 

 water. Each piece was thus moored to a particular place, and, be- 

 cause of its buoyancy, assumed a position of stability. The threads 

 were about 1| inch long, so that a piece of ice, when depressed 

 sideways and then left to itself, rose in the water as far as it could, 

 and into its stable position, with considerable force. When, also, a 

 piece was turned round on its loop as a vertical axis, the torsion 

 force tended to make it return in the reverse direction. 



Two similar blocks of ice were placed in the water with their 

 opposed faces about two inches apart ; they could be moved into 



