35$ CONTRACTION OF WATER BY HEAT. 



The general faft relative to the fubject of inquiry. The general import of 

 caufefice^cold them * s ' { ^ 1 water wn *ch is ice-cold, or a few degrees 

 water to contraft warmer, when heated, becomes fpecifically heavier, — that 



to 40 , and water of 40° when heated becomes fpecifically lighter,— 

 afterwards to , , _ , , * „ \ , 1 1 • 



cj*j>and. tnat water above 40 , by the lofs of heat, or by cold, is 



rendered fpecifically heavier ; and that water below 40° is, 

 by the fame caufe, rendered fpecifically lighter. 



Such being the general import, the conclufion is irrefiftible, 

 that heat, in low temperatures, caufes water to contract, and 

 at fuperior temperatures to expand. The opinion, therefore, 

 is founded in truth, that water pofleflfes a peculiarity of con- 

 stitution in relation to the effects of caloric, and that it is, 

 within a fhort range of temperature, an exception to the 

 general law of. " expanfion by heat." 

 Thegreateft So far as lean judge from thefe experiments, lam dif- 



denfuy Hesb e . rj to j, e ]j eve t j lat t j ie po ; nt at w hi c h the change in' the 

 tween 39!'' and r * , 1 1 i- 



40?, conftitution of this fluid in relation to heat takes place, lies 



between 39l°, and the 4.0th degree. 



I am not at prefent aware of any objection to the method X 

 have followed in eftablifhing this lingular anomaly, and in re- 

 moving any doubts which may have arifen from the unavoid, 

 able influence which the internment muft have in the mode of 

 conducting the inveftigation that had previoufly been adopted. 

 Thefe exneij- The plan of operation above defcribed, however, only af- 

 ments /hew the ce rtains the fact ; it gives no data for ascertaining the amount 

 change, but not °f tne anomalous effect of heat. 



its amount. j have already ftated, that M. de Luc alledged, that from 



expanfions and tne temperature of 41°, the expanfion occafioned by colcj 



contractions be was very nearly equal to that produced by the fame number. 



^uatintervals °^ degrees °f ^eat > anc * confequently that water poflelTes the 



from4o° ? fame denfity at any given number of degrees of temperature 



above and below 41 p . The firft experiments of Mr* Daltorj 



appeared to confirm this opinion, and to enlarge the range to 



which it applied, by extending it to temperatures as far 



below 32°, as water allows itfelf to be cooled before it begins 



to freeze. From oue circumftance that constantly occurred, 



I am inclined to think, that the amount of the dilatation by 



cold is inferior to that caufed by heat. 



During the heating or cooling of water below 40°, the dif- 

 ference of temperature between the top and bottom of the 

 fluid was lefs than what occurred during the cooling or heat, 



in§ 



