272 The Temperature of Water 



appear. It was at the bottom of the water, where this 

 liquid was in contact with the mercury, that the ice 

 formed. 



The layer of water which rested immediately on the 

 surface of the mercury having been cooled to about the 

 temperature of 41 F., where the density of water is at 

 its maximum, the particles of this water, which were 

 then in immediate contact with the mercury, losing still 

 more of their heat, became of necessity less dense, and 

 had consequently a tendency to leave the bottom of the 

 water and to ascend upwards ; but the rapidity with 

 which they were cooled by the mercury was so great 

 that they were frozen before they could escape from the 

 cooling influence of this cold body. 



After all that I have said about the warm and cold 

 currents which take place in a liquid which is warmed 

 or cooled, it might perhaps be thought that I regard 

 these currents as composed of single particles of the 

 liquid, which, having been in immediate contact with 

 the body which gives or which receives the heat, are 

 all of the same temperature. I am all the farther from 

 holding this opinion, since I know from the results 

 of several experiments made expressly for elucidating 

 this point, (and which I shall have the honor of present- 

 ing to the Class on another occasion,) that a liquid 

 current cannot pass through another liquid mass which 

 is at rest, and which is of the same kind and of about 

 the same specific gravity, without producing a per- 

 ceptible mixture of the two liquids ; much less, therefore, 

 can a small current of warm water pass without mixing 

 through a mass of cold water ; and the farther it advances 

 the more it will be mixed, and the more, in consequence, 

 will its temperature be found to be lowered. 



