at its Maximum Density. 269 



contact with the cold water that the vertical descending 

 currents could exist by which the thermometer was at 

 length heated. At the beginning of the experiment 

 made with the tin ball warmed in boiling water, the 

 particles of water which were in immediate contact with 

 the conical point while it was still very warm, were 

 heated to a temperature higher than that at which the 

 density of water is at a maximum, and the density of 

 these particles being diminished by this high degree of 

 heat, the vertical currents in the cold water were at the 

 beginning ascending currents, as I satisfied myself by 

 means of a small thermometer placed by the side of the 

 conical point at a distance of T 2 of an inch from its base, 

 and immediately below the surface of the cold water : 

 this thermometer began to rise very rapidly as soon as 

 the warm metallic point was plunged into the cold 

 water. 



Another small thermometer, the bulb of which was 

 situated at about the same distance from the axis of the 

 conical projection, but -J- of an inch below the surface of 

 the cold water, preserved throughout the entire experi- 

 ment the appearance of perfect rest. 



The results of this last experiment are all the more 

 interesting because they afford a demonstrative proof that 

 it was neither by a direct communication of heat in the 

 water, which was at rest, from molecule to molecule, de 

 proche enproche, nor by calorific radiations passing through 

 the water, that heat was communicated from the metallic 

 point to the bulb of the thermometer, but actually by a 

 descending current of warm water ; for it is perfectly 

 evident that if this heat had been communicated either 

 by a direct transfer in the water from molecule to mole- 

 cule or by calorific radiations passing from the surface 



