CONTRACTION OF WAT1R B.Y HEAT. 



357 



Applied to the middle of a column of ice-cold water. The 

 heated portion has an equal (hare of the column of cold fluid 

 above it and beneath it. There is nothing to determine its 

 courfe in one direction or another, excepting its actual change 

 of denfity. 



The thermometer evinces that the warm current fets down- Whence it 1$ 

 wards, and carries the increafed temperature to the bottom, ^^cuiTentof 

 There, this inftruraent indicates the fucceffive rife of feveral water between 

 degrees, before the furface indicates the fmalleft acquisition llf c ™dJ 9 b* 

 Or heat. Mu f e 'Jcnfer and 



The inference is plain, that the cold water is contracted by that when the 

 ., , ■ J temperature wat 



iheheat. more than 39+ 



The change of the effect of heat is equally well illuftrated the«ww cur- 

 by .hi, experiment. «££££ 



No fooner did the inferior portion attain the temperature of 

 39°, than the heated fluid altered its courfe, and, by amend- 

 ing, carried the increafe of temperature very rapidly to the 

 furface, fo that it foon furpafled the bottom, and continued to 

 rife, while the other remained ftationary. 



Exp. VJ. I filled the jar ufed in the laft experiment with Exp. 6. The 



water of temperature 39|°, the air and the fupport being at fiXd^thwatcf 



39°. Difpofing the thermometers in the ufual manner, I in- at 39*° and a 



troduced a mixture of fnow and fait into the bafon. freezing mix- 



ture applied to 



At commencement, 

 In 10 minutes, 



_25 



^-35 



;_ 55 



— an hour and 10 min, 

 35 



— 2 hours, 



Bottom. 

 39.5 

 39 + 

 39 + 

 39 

 39 

 39- 

 39- 

 39- 



Top. 

 39.5 

 38 + 

 36.5 

 36- 

 35 



34 + 

 34- 

 33 + 



Air. 

 39* 



the middle zone. 

 The fluid at 

 bottom wag 

 fcarcely changed, 

 but that at top 



► # : » At this time fr0 *«* 



ice began to be 



formed pn the 



fide of the vef- 



fel. 



This experiment fpeaks in as decided language as the pre- So that the 

 ceding. It (bows that when a portion, in the middle of a water cooled^ 

 column of water at temperature 39.5 is cooled, the colder rifeTyexpan- 

 fluid rifes, and does not defcend through the warmer mafs, fion. 

 and prefents the unequivocal demonstration, that water of 

 temperature 39|° is actually expanded by lofing heat. 



The different experiments which I have in detail recorded, 

 agree perfectly with each oth«r in the. evidence they give 



relative 



