j 7 1 Great ^uaniiuts ef Heat tranfmitled iy Sea Water. 



the lakes, and the trees, be defended againft the cold winds from the poles, it may be adced, 

 how this inundation of cold air is to be warmed ? The Count anfwers. By the waters of 

 the ocean, which there is the greateft reafon to think were not only defigned principally for 

 that ufe, but particularly prepared for it. 



Sea water contains a large proportion of fait in folution ; and thecondcnfation of a faline 

 folulion on its being cooled, follows a law which is extremely different from that obferved 

 in regard to pure water, and which (as may cafily be fhown) renders it peculiarly well 

 adapted for communicating heat to the cold winds which blow over its furface. 



As fea water continues to be condenfed as it goes on to cool, even after it has palTed the 

 point at which frefh water freezes, the particles at the furface, inftead of remaining there, af- 

 ter the mafs of tJie water had been cooled to about 40", and preventing the other warmer par- 

 -ticles below from coming in tlicir turns, and giving off their heat to the cold air (as we have feen 

 always when frefh or pure water is fo cooled) — thefe cooled particles of fait water defcend 

 as foon as they have parted with their heat, and in moving downward force other warmer 

 particles to move upwards ; and in confequencc of this continual fucceffion of warm parti- 

 cles which come to the furface of the fea, a vafl deal of heat is communicated to the air- 

 incomparably more tlian could poflibly be communicated to it by an equal quantity of 

 frefli water at the fame temperature, as will appear by the following computation : 



Without taking into the account that very great advantage which fea water poflcfles 

 over frefh water, confidered as an equalizer of the temperature of the atmofphere, which 

 arifes from the comparative lownefs o/the point of its congelation j fuppofing even fea water to 

 freeze at as high a temperature as frefh water, namely at 32° ; and fuppofing (what is (Iridlly 

 true^ that as foon as either fea water or frefli water is frozen at its furface, and this ice 

 covered with fnow, the communication of heat from the water to the atmofphere ceafes 

 almoft entirely ; the Count proceeds to determine how much more heat would, even on this 

 fuppofition, be communicated to the air by fait water than by frefh water, after both have 

 arrived at the temperature of 40°. 



When frefh water, in cooling, has arrived at this temperature, it ceafes to be farther con- 

 denfed with cold, and its internal motions (which, as hath already more than once been 

 obferved, are caufed folely by the changes produced in the fpecific gravity of its particles) 

 ceafe of courfe, and ice immediately begins to be formed on its furface : but as the conden- 

 fation of fait water goes on as its heat goes on to be diminiflied, its internal motions will 

 continue ; and it is evidently impoffible for ice to be formed at its furface, till the whole 

 mafs of the water has become ice cold, or till its temperature is brought down to the fiip- 

 pofed point 32'. It would therefore ^ive off a quantity of heat equal to 8 degrees at leaft 

 of Fal-irenheit's thermometer more than the frefh water would part with before ice could 

 be formed on its furface. 



To be able to form an idea of this enormous quantity of heat, we have only to recollect 

 ■what has already been faid, and we fliall find reafon to conclude tliat it would be fufTicient 

 to melt a covering of ice equal in thicknefs to •/■jths of the depth of the fea. It %vould there- 

 fore be fuflicicnt in that part of the North fea (lat." 67) where Lord Mulgrave founded at 

 the depth of 4680 feet, to melt a cake of ice 265 feet thick. 



But 



