378 BENSITV OF WATE^l,' 



perhaps appear in a future volume. My prefent obje«!il is to 

 fliew that the refults oF Dr. Hope's experiments are explicable 

 on the fuppofition of water being denfeft at 36^, but on no 

 other. 

 Obfervations on ' Dr. Hope and myfelF concur in the opinion that water is 

 the expanfions (Jepfeft at fome one point of temperature, and that above and 



of water on each ' ^ 



fide of its point below that point it expands alike by heat and cold in a gradu- 

 of greateftden- ^\\y increafmg manner. De Luc vi'as the firft to obferve that 

 the expanfion is the fame quantity for the fame number of de- 

 grees, whether of increafe or diminution of temperature; the 

 remarkable fa6l was extended by my former experience from 

 ^ range of 8° to 25" or more, above and below the ftationary 

 point. I have lately examined (his fa6t with greater attention 

 to precifion than formerly, and find that it is accurate, except 

 that the expanfion for degrees below the ftationary point is al- 

 \vays fomewhat more than for a correfponding number of de- 

 grees above the faid point. Thus, water is flationary in a 

 glafs thermometer at 42°; if heated to 75*' by the mercurial 

 fcale, it expands very confiderably ; if plunged into a frigori- 

 fic mixture of IS'', it falls to 42°, and then expands again 

 to the fame point of 75°, at which it remains flationary as 

 long as continued in the mixture. It may be remarked too, 

 that congelation rarely if ever takes place in the bulb, when 

 the mixture is not below 15", which may eatily be procured 

 by putting fnow into water faturated with common fait. Hence 

 we fee that 29° below, afford the fame expanfion as 33° above 

 the flationary point. This, I imagine, is occafioned by the 

 error attached to the equal divifion of the mercurial fcate. 

 For a fmall number of degrees, however, we may admit that 

 the expanfions for correfponding intervals above and below 

 are equal; hence we obtain the following tableof correfpond- 

 ing temperatures at which water is of the fame denfity. 



at 36^ 



Siippofing 



greateft denfity at 

 (•39° and 41" 

 I 38 • 42 



40? 





Correfpond- 



\ 37 43 



C 



orrefpond- 



ing denfi- 



J 36 44 





ing denfi. 



ties will 



135 45 





ties will 



hit at 



/ 34 46 



1 33 47 



1 32 48 





beat 



(35° and 

 34 

 32 



]31 



J 30 



I 29 



(^28 



ST** 



38 



39 



40 



41 



42 



43 



44 



Dr. 



