164 On the Contract ion of Water lij Heat. 



Did water observe the usual law, and lose volume along 

 vith tenipcra'iurc, this experiment, by its long duration, 

 afiordtd ample time tor the manifestation of it. 



For not less than two days did ice-cold water maintain 

 possession of'the top, and for the same period the temperature 

 ^t the bottom never fell below 39". No current, there- 

 fore, of cold and condensed fluid moved from the surface, 

 to affect the inferior thermometer, or to attest the con- 

 traction of water by cold. 



This experiment, however, I must remark, does not 

 Avarrant the conclu?if)n, that the water is actually expand- 

 -ed, though it in no degree opposes it. It proves no more, 

 than that the contraction ceases at 40°; and that water of 

 32" is not more dense than of 39" or 40°. Nay, some may 

 perchance allege, that it does not prove so nuich ; con- 

 ceiving, that if at 40" the contraction, without ceasing al- 

 together, becomes very inconsiderable, the difference of 

 density (jccasioned bv the subsequent reduction of tem- 

 perature may be so very trifling, as not to enable the cold 

 particles to take that situation which their gravity assigns to 

 'them, in opposition to the inertia and tenacity of the sub- 

 jacent mass; and therefore that the colder, though heavier 

 fluid, may be constrained to remain above. That this al- 

 ieg-ation should have no weight attached to it, the circum- 

 stances of the succeeding experiment will clearly show, as 

 I shall soon notice. 



Before quitting the consideration of the present experi- 

 ment, it may be worth while to remark, that it may seem 

 rather surprising, that the bottom of the tluid was not ap- 

 parently affected in its temperature by the ice which so long- 

 occupied its surface. It might be expected, though no cold 

 currents descended from above, that the caloric should be 

 conducted from below, and tliat the temperature should 

 by that have been reduced*. I suppose that the caloric 



did 



* This experiment mav perhaps be thought to give countenance to the 

 rpmion of the very ingenious Count Rumford, that fTuids cannot conduct 

 lieat, an.! that no interihange ot heat can take pl:;ce between the particles 

 of bod Ls in a fluid stale, seeing that for two days the fluid at the bottom of 

 the ves ;^.l never fell below S9", ihough the surface w;is at aL'". 



Fro,n ttie fircumstance^ detailed in his seventh essay, the Count conchi- 

 did, iliat b(a cannot desrcnd in a fluid. From the present, it miglit with 

 fqunl iistif i- he iiite. red, that heat cannot ascend. 



Ha-j 5 „„t lh<- t'i;lle-t conviciion that this celebrated philosopher has pu-h- 

 td h' ideas t<'>i f.r. ! might be disposed to consider this experiment as ac- 

 c- dinT ^'vel\ withthi hypfithesis. 



boon -ifter the iniCiLsting speculations of the Count appeared, 1 began »o 

 iu e'tig »•'>■' he .si;li'"'i'i ; .ir.il, by a pretty long train of exporin.ents, which I 

 h^yjai>BJ:tl'V tiikfu jh opportunity of detailing in my lectures, satisfied 



myself 



