1858.] GRADATION OF TEMPERATURE IN FREEZING WATER. 229 



upon a horizontal glass rod passing through two holes in the 

 plates of ice, so that the plane of the plates was vertical. Con- 

 tact of the even surfaces was obtained by means of two very 

 weak pieces of watch-spring. In an hour and a half the cohe- 

 sion was so complete, that, when violently broken in pieces, 

 many portions of the plates (which had each a surface of 20 

 or more square inches) continued united. In fact, it appeared 

 as complete as in another experiment where similar surfaces 

 were pressed together by weights. I conclude that the effect 

 of pressure in assisting " regulation" is principally or solely due 

 to the larger surfaces of contact obtained by the moulding of the 

 surfaces to one another. 



3. Masses of strong ice, which had already for a long time 

 been floating in unfrozen water-casks, or kept for days in a 

 thawing state, being rapidly pounded, showed a temperature of 

 0-3 Fahrenheit below the true freezing point, shown by deli- 

 cate thermometers (both of mercury and alcohol), carefully 

 tested by long immersion in a considerable mass of pounded ice 

 or snow in a thawing state. 



4. Water being carefully frozen into a cylinder several 

 inches long, with the bulb of a thermometer in its axis, and the 

 cylinder being then gradually thawed, or allowed to lie for a 

 considerable time in pounded ice at a thawing temperature, 

 showed also a temperature decidedly inferior to 32, not less, I 

 think, than 0*35 Fahrenheit. 



I think that the preceding results are all explicable on the 

 one admission, that Person's view of the gradual liquefaction 

 of ice is correct (Comptes Rendus, 1850, vol. xxx. p. 526),* or 

 that ice gradually absorbs latent heat from a point very sensibly 

 lower than the zero of the centigrade scale. 



* Quoted by me in 1851, in my sixteenth letter on Glaciers [p. 225 above]. 

 [See also the anticipation of the fact in my paper of 1846, note to page 156 of this 

 volume. Even in 1851 I was unacquainted with Mr. Faraday's experiment, the 

 publication of which was, so far as I know, confined to the journals quoted at page 

 228. As I was in Germany at the time, they naturally escaped my notice. To 

 facilitate reference to Mr. Faraday's- observation, I have, as already mentioned, 

 thought it well to reprint the report of it in the Appendix.] 



