GREATEST DENSITY OF WATER. PS 



VI. 



■Facts tending to decide the Suejiion, at what Point of Temperature 

 Water pojfejfes the greateft DenjHy. In a Letter from Mr. 

 John Dalton. 



To Mr. NICHOLSON. 

 SIR, 



iiCCORDING to the doctrine in moft of our books treat- Genera! notion 



ihg of the elements of chemical fcience, it is confidered as a denfeilatAo 



decided fact, that water is of the greateft denfity at or near &c. 



40° of temperature of Fahrenheit's fcale ; and that, ahove or 



below that temperature, it expands alike by heat or cold for 



a certain number of degrees. I have taught a different doc- The autn °Cs 



r r ■ n i • ' i • • i -irn doctrine that 



trine tor iome time pair ; which is, that water is denied at , 2 o ; s tne po ; n t 



32 Q , or the freezing point, and that it expands alike above or " greateft den- 



and below that point for at lead 25° (provided it does not ' y ' 



freeze), and that (he quantity of expanfion is as the fquare 



of the temperature, reckoned from 32°, up or down; that 



is, if the expanfion from .'32 to 42° be denoted by 1, that from 



32 to 52° will be denoted by 4, and that from 32 to 62° by 9, 



tyc. or nearly fo ; the deviation from ftrici accuracy being, 



as I conceive, occafioned by (he mercurial thermometer not 



being an exact meafure of temperature: the expanfion at 22* 



is likewife 1, at 12° it is 4, and at 2° it is 9, fyc; the fame 



below as above the freezing point. In conlequence of thi*, Experiments 



a gentleman of profeflional eminence has undertaken to exa- P o°"^e for 



mine the fubject anew; and has been led, by an ingenious conclufion, 



train of experiments totally different from the following, to 



decide in favour of the common notion, that water is denfeft 



about 40°. Thefe experiments of his will foon be published. The author re- 



I am ftill, however, decidedly convinced, that my opinion ^ a ; ,ns hls . ?' 



nion, and in- 

 above ftated is true, and that principally from the fa£ts I am vires other expc* 



about to ftate, which thofe who adopt the common opinion nments « 

 mifft fee the abfolute neceffity of explaining upon their prin- 

 ciple, or otherwife, of controverting the facts themfelves. 

 As this feafon of the year is moft convenient for experiments 

 of this nature, I am the more folicilous to have the facts an- 

 nounced, leaving all explanation for the prefent. They are 

 of a very Ample nature, and may be inveftigated with little 

 trouble and expence. 



A number 



