1 70 On the Contraction of Water hf Heat. 



sesses a p^culiai itv of constitution in relation to the effects 

 of caloric, and liiat it isj within a short range of tempera- 

 ture, an exception to the general law of " expansion by 

 hcai." 



So far as 1 can jiulge from these experiments, I am dis- 

 posed to believe that the point at which the change in the' 

 constitution of this fiuid in relation to heat takes place, lies 

 between the snv" and the 40th degree. 



I am not at present aware of any objection to the method 

 I have followed in establishing this singidar anomaly, and 

 in removing anv doubts which mav have arisen from the 

 unavoidable uiiluence vihich the instrument nmst have in 

 the mode of conducting the investigation that had previ- 

 ously been adopted. 



The plan of operation above described, liowever, only 

 ascertains the fact ; it gives no data for ascertaining the 

 amount of the anomalous eflVct of heat. 



I have already stated, that M, de Luc alleged, that from 

 the temperature of 41", the expansion occasioned bv cold 

 was very nearly equal to that produced by the same num- 

 ber of degrees of heat ; and consequently that water pos- 

 sesses the same density at any given number of degrees of 

 temperature above and below 41°. The ilrst experiments 

 of Mr. Dalton appeared to confirm this opinion, and to 

 enlarge the range to which it applied, bv extending it to 

 temperatures as far below 3'2°, as water allows itself to be 

 cooled before it begins to freeze. From one circumstance 

 that constantly occurred, I am inclined to think, that the 

 amount of the dilatation by cold is inferior to that caused 

 by heat. 



During the heating nr cooling of water below 40", the 

 difference of temperature between the top and bottom of 

 the fluid was less than what occurred during I he cooling or 

 heating of the fluid through the same number of decrees 

 above it ; and I conceive that, when other circumstances, 

 feut particularly the rate of the change, are alike, the dif- 

 ference of temperature between the upper and lower parts 

 of the fluid, as it depends upon, may prove a measure of, 

 the difl'erence of density. 



Alcohol, when heated or cooled, presents, by reason of 

 its greater expansibility, a greater difi'erence of temperature 

 m these situations than water; and upon the same principle 

 I inter, that water from 40" is more expanded by an equal 

 number of degrees of elevation than of depression. 



As the concurrence of the testimony of the experiments 

 above related with the general opinion, will probably re- 



aiove 



