Coiifi-qiienees which ivotdd enfiie if TVater could contrsH t'lU frozen . 571 



cooling tny given number of degrees, is to the given quantity of water as the number of 

 degrees which it is cooled to 140°. 



Hence it follows, that when the tennperature of the water is 8° above the freezing point. 

 It gives off in cooling.down to that temperature, as much heat as would melt .-J-jths or ^\ths 

 of Its weight of ice : the water therefore which is cooled from the temper.uuve of 40" to 

 that of ;i2°, if it be 35 feet deep, will give off as much heat, in being fo cooled, as would 

 melt a covering of ice two feet thick. 



But this even is not all ; for, as the particles of water, on being cooled at the furface, 

 would in confequence of the increafe of their fpecific gravity, on parting with a portion of 

 their heat, immediately defcend to the bottom, the greatelt part' of the heat accumulated 

 during the fummer in the earth on which the water repofes would be carried off and loit 

 before the wnter began to freeze ; and when ice was once formed, its thicknefs would in- 

 creafe with great rapidity, and would continue increafing during the whole winter. And 

 It feenis very probable, that, in climates which are now temperate, the water in the large 

 lakes would be frozen to fuch a depth in the courfe of a fevere winter, that the heat of the 

 enfuing fummer would not be fulEcient to thaw them; and Ihould this once happen, the 

 following winter could hardly fail to change the whole mafs of its waters to one folid body 

 of ice, which never more could recover its liquid form, but mull remain immoveable till 

 the end of time. 



In the month of February, after a froft which had laded a month, the temperature of 

 the air being 38°, M. De Sauffure found the temperature of the water at the Lake of Ge- 

 neva, at the furface, at 41% and at the depth of 1000 feet, at 40°. Had the froft conti- 

 nued but a little longer, ice would have been formed ; but had the conflitution of water 

 been fuch, that the whole mafs of that fluid in the lake mud have been cooled down to the 

 temperature of 32° before ice could have been formed, this event could not have happened 

 till the water had given off as much heat as would be fulEcient to melt a covering of ice 

 above 57 feet thick. 



This quantity of heat would be fufficient to heat to the point of boiling a quantity of ice- 

 cold water as large as the lake, and 49 feet deep. 



When we trace ftill further the aftonidiing effefts which are produced in the world by 

 the operations of that fimple law, which has been found to obtain in the condenfation of 

 water on its being deprived of heat, we diall find more and more rcafon to admire the wif- 

 doin of the cotitrivance. 



That high latitudes miglit be habitable, it was neceffary that vegetables fliould be proi 

 te<f^ed from the effe£ls of the chilling frods of a long and fevere winter ; but if it be true 

 that watery liquids do not part with their heat but in confequence of their internal motion, 

 and if thefe motions are occafioned merely by the change produced in the fpecific gravity of 

 thofc particles of the liquid which receive heat, or which part with it, who does not fee 

 how very powerfully the fudden diminution and final ceffation of the condenfation of 

 water in cooling, as foon as its temperature approaclics to the freezing point, operates to 

 prevent the fap in vegetables from being frozen ? 



13ut if, for the purpofes of life and ycgct.ition, it be neceffary that the ground, the rivers, 



4 D 2 the 



