Bottom of a Vcjjel of BoiUng Wafcy. 347 



It certainly ran out of the circular excavation in the middle of the ice ; and though it 

 inight at firft appear difficult to explain the fafl, and to fiiew how this hot water could ar- 

 rive at that place ; yet it was quite evident that the immediate caufe of the motion of this 

 ftream of water could be no other than its fpecific gravity being greater than that of the 

 reft of the water at the fame depth; and that this greater fpecific gravity was at the fame 

 time accompanied by a higher degree of heat, is evident from the deep channel which this 

 ftream had melted in tlie ice, while other parts of the furface of the ice at the fame level 

 were not melted by the water which refted on it. 



This experiment, though attended with remarkable clrcumftances, did not clearly fhew 

 that the fufion of the uncovered part of the ice had been efl'etled by radiant heat. It oc- 

 curred to the author, t'lat radiant heat, like light, might probably be rcflefted downwards 

 in part from the internal furface of the water; and confequently, that it might be expefled 

 that a light black body, namely, a circular piece of deal board, covered over with black filk, 

 Tvould abforb a portion of the whole body of rays which were directed to the ice. This 

 trial was made, but with no fenfible effeil. 



As it is uncertain whether heat in the radiant ftate can be reflefted in this manner, 

 the experiment may perhaps be confidered as likely to afford a lefs equivocal conclufion 

 than might have been obtained from the application of a poliflied metallic furface to the 

 fuperior termination of the cylinder of water. But the appearance of a channel worn in 

 the plate of ice in the preceding experiment gave rife to meditations which clearly pointed 

 out the manner in which the ice was melted, and rendered the attempts to detedi: the fup- 

 pofed operation of latent heat unnecefTary. The Count's explanation, in his own words, 

 is as follows : 



Though it is one of the moft general laws of nature with which we are acquainted, that 

 all bodies, folids as well as fluids, are condenfcd by cold, yet, in regard to water, there ap- 

 pears to be a very remarkable exception to this law. Water, like all other known bodies, is 

 indeed condenfed by cold at every degree of temperature which is confiderably higher than 

 that of freezing; but its condenfation, on parting with heat, does not go on till it is changed 

 to ice ; but when in cooling its temperature has reached to 40 degrees of Fahrenheit's fcale, 

 or eight ilegrees above freezing, it ceafes to be farther condenfed ; and on being cooled Hill 

 farther it actually expands, and continues to expand as it goes on to lofe more of its heat, 

 till at laft it freezes; and at the moment when it becomes folid, and even after It has become 

 foljd, it expands ftill more on growing colder. This fad, which is * noticed by M. de Luc, 

 in his excellent Treatife on the Modifications of the Atmofphere, has fiiice been farther 

 inveftigated and put beyond all doubt by Sir Charles Blagden. (See Philofophical Tranf- 

 actions, vol. Ixxviii.) 



Now, as water in conta£l with mehing ice is always at the temperature of 32", it is evi- 

 dent tliat water at that temperature mud be fpecifically lighter than water which is eight 

 degrees warmer, or at the temperature of 40''; confequently, if two parcels of water at thcfe 

 two tciTiperaturcs be contained in the fame vcflcl, that which is the coldeft and lightcfl mud 

 neccirarily give place to that which is warmer and heavier, and currents of the warmer 

 water will dcfcend in that which is colder. 



• Tlic fimplc faa was alfu cbfcrvol l)y ilic cvkbiatiJ Rubcrt r."ylc. 

 y y 2 



