J 



82 On the CONTRACTION- 



freezing point. The water began inftantly to rife as before, and 

 when it had afcended about one-fourth of an inch in the ftem, 

 the vefTel was taken out, the whole water remaining fluid. 



These experiments, fupported by others of a fimilar nature, 

 communicated by Dr Slare to the Society on the 20th of the 

 /ame month, appear to have fatisfied its members, in general, of 

 this fadl, that water, when on the point of congealing, and while 

 ftill fluid, is adtually fomewhat dilated previous to the remark- 

 able expanfion which accompanies its converfion into ice. 



Dr Hooke, however, continued unfliaken, and retained the 

 doubts he had expreflTed. 



Remarkable as the fadt, as now ftated, mufl: have appeared, 

 it feems not to have excited particular attention, nor to have foli- 

 cited more minute examination ; and indeed though philofophers 

 did not lofe fight of it, yet for near a century no one inveftiga- 

 ted it more carefully. Mairan, in his treatife on ice in 1749, 

 and Du Crfst in his difl"ertation on thermometers in 1757, ap- 

 pear to be well aware of this property of water ; but it is to M. 

 De Luc that we owe the knowledge of the leading and more in- 

 terefl;ing circumfl;ances, (vide Recherches, &c. 1772). 



Having devoted his attention to the examination and im- 

 provement of the thermometer, he was naturally led to the in- 

 vefligation, while engaged in afcertaining the phenomena of the 

 expanfion and contra6lion of different fluids by heat and cold. 



He employed in his experiments thermometer glafl"es ; and the 

 included water, at or near the term of liquefadlion, defcended in 

 the flem, and appeared to him to fufi'er a diminution of bulk by 

 every increafe of temperature, till it arrived at the 4ifl: degree. 

 From this point its volume increafed with its temperature, and it 

 afcended in the tube. This fluid, when heated and allowed to 

 cool, feemed to him to contradl in the ordinary way, till its tem- 

 perature funk to the 41 °, but to expand and increafe in volume, 

 as the temperature fell to the freezing point. 



The 



