CONTRACTION OF WATER BY HL^AT. 35$ 



tng of the fluid through the fame number of degrees above 

 k ; and I conceive that, when other circumftance s, but par- 

 ticularly the rate of the change, are alike, the difference of 

 temperature between the upper and lower parts of the fluid, 

 as it depends upon, may prove a meafure of the difference of 

 denfity. 



Alcohol, when heated or cooled, prefents, by reafon of its 

 greater expanfibility, a greater difference of temperature in 

 thefe fituations than water; and upon the fame principle I 

 infer, that water from 40° is more expanded by an equal 

 number of degrees of elevation than of depreflion. 



As the concurrence of the teftimony of the experiments it is a difficult 



above related with the general opinion, will probably remove problem toex- 



, , r ^- , r r r> • • plain, how thefe 



every doubt refpecting the matter of tact, it remains a very contrary changes 



difficult problem for thofe who are fond of philofophical in- by heat are 

 veftigation, to explain how heat (hall occafion' in the fame 

 fluid, without producing any alteration of mechanical form 

 of chemical condition, at one time contraction and at another 

 expanfion, and to reconcile the contractive effect to the con- 

 ceived notions of the mechanifm of the operations of this 

 .energetic agent. 



When heat caufes expanfion, it is imagined to act by indue- Tne queftioa 

 ing a repulfion among the particles of bodies, which, oppofing 

 and overpowering the cohefive attraction, caufes the particles 

 io recede. x 



In what manner, then, the addition of heat can occafion, or 

 allow, the particles of water to approach each other, and how 

 the fubtraction of it can make them retire to a greater diftanGe, 

 I confefs I can in no meafure comprehend. 



An explanation, abundantly plaufible at firft view, very s * r Charles 

 i'i r r, • r ir i ex Blagden's ex- 



readily luggefts ltlelt to every one who is aware or the great pt ana ti n j viz. 



and forcible expanfion which happens to this fluid at the 

 moment of its congelation. It it jftated by §ir Charles Blag- 

 den, in the paper already quoted. 



The remaikable dilatation which water experiences at the As water ex-^ 

 inftant of being converted into ice, is very generally afcribed, by^h-tueof a'" S 

 and I prefume very properly, to a new arrangement which the new arrange- g 

 particles aim me, determined probably by their polarity ; by me " t |° * c 

 which one fide of the particle A is attractive of one fide of B; 

 %yhjle it is repulfive qf another. 



Now, 



