382 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 (tern, 

 the veffel 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 

 fame month, appear to have fatisfied its members, in general, of 

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

 {till fluid, is actually fomewhat dilated previous to the remark- 

 able expanfion which accompanies its converfion into ice. 



Dr Hooke, however, continued unfhaken, and retained the 

 doubts he had expreffed. 



Remarkable as the fact, as now ftated, muft 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 inveltiga- 

 ted it more carefully. M air an, in his treatife on ice in 1749, 

 and Du Crest in his difTertation 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- 

 terefting circumftances, (vide Recherches, &c. 1772). 



Having devoted his attention to the examination and im- 

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

 vestigation, while engaged in afcertaining the phenomena of the 

 expanfion and contraction of different fluids by heat and cold. 



He employed in his experiments thermometer glaffes ; and the 

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

 the ftem, and appeared to him to fuffer a diminution of bulk by 

 every increafe of temperature, till it arrived at the 41ft 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 contract 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 



