380 On the CONTRACTION 



late, and continues to dilate, as the temperature falls, till con- 

 gelation adually commences, whether this occurs as foon as the 

 water reaches the 32°, or after it has defcended any number of 

 degrees below it. 



Supposing this peculiarity of water to be eftablifhed, it muft 

 appear, indeed, a very odd circumftance, that heat fliould pro- 

 duce contradlion in this fluid, while it caufes expanfion in other 

 bodies ; and no lefs ftrange, that within one range of tempera- 

 ture it fliould contract, and in another expand, the very fame 

 fubftance. Before a deviation from fo general a law fliould be 

 received as matter of facft, the proofs pf its exillence ought to be 

 clear and indifputable. 



The experiments hitherto publiflied, from which this Angula- 

 rity has been deduced, have all of them been performed upon 

 water contained in inftruments fliaped like a thermometer glafs, 

 and confifting of a ball with a flender fl:em ; and the expanfive 

 or contratHive effecfls of heat and cold have been inferred, from 

 the afcent or defcent of the fluid in the ftem. 



To fuch experiments it has been objedled, that the dimenfions 

 and capacity of the inftrument undergo fo much change, from 

 variation of temperature, that it is difficult, if not impoflible, to 

 determine how much of the apparent anomaly ought to be im- 

 puted to fuch changes, and that it is not improbable that the 

 whole of it may be afcribed to them. 



The objedl of this paper, which I have now the honour to 

 read to the fociety, is to prove by a fet of experiments, conduc- 

 ed in a manner altogether different, that the common opinion is 

 founded in truth, and that water prefents itfelf as that fl;range 

 and unaccountable anomaly which I have already defcribed. 



It is worth while, before detailing my experiments, to give a 

 fliort account of thofe obfervations which led to the difcovery of 

 the fadl, and which in fuccefllon have extended our knowledge 

 of it, as well as of thofe obfervations which have at different 

 periods been offered to difcredit, and to bring it into doubt. 



The 



