in Fluids. 287 



not be propagated downwards in water as long as that 

 fluid continues to be condensed with cold ; and that it is 

 only in that direction (downwards) that it can be propagated 

 after the water has arrived at that temperature where it 

 begins to be expanded by cold, which has .been found 

 to be at about the 4Oth degree of Fahrenheit's scale. 



Reasoning on these principles, we are led to this re- 

 markable conclusion ; namely, that water which is only 

 eight degrees above the freezing-point, or at the temperature 

 of 40, must be able to melt as much ice in any given time, 

 WHEN STANDING ON ITS SURFACE, as an equal volume of 

 water at any higher temperature, EVEN THOUGH IT WERE 



BOILING HOT. 



My philosophical reader will doubtless think that I 

 must have had no small degree of confidence in the 

 opinion I had formed on this interesting subject, to have 

 had the courage to make, even in private, the experiments 

 which were necessary to ascertain that fact. 



Experiment No. 19. 



Into a cylindrical glass jar, 4.7 inches in diameter and 

 13.8 inches high, I put 43.87 cubic inches, or i Ib. iif 

 oz. Troy, in weight, of water, and placing the jar in a 

 freezing mixture, composed of pounded ice and common 

 sea-salt, I caused the water to freeze into one compact 

 mass, which adhered firmly to the bottom and sides of 

 the jar, and which formed a cylinder of ice just three 

 inches high. 



Had the bottom of the jar been quite flat, instead of 

 being raised or vaulted, the cylinder of ice would have 

 been no more than 2.67 inches high. 



As soon as the water in the jar was completely frozen, 

 the jar was removed from the freezing mixture and 



