in Fluids. 357 



When a doubt arises with regard to the possibility of 

 any operation of a peculiar kind, which is supposed to 

 take place, in any process of nature among those infi- 

 nitely small integrant particles of bodies which escape, 

 and must ever escape, the cognizance of our gross organs, 

 however they may be assisted by art, the shortest way 

 of deciding the question is to put the known powers of 

 nature in action under such circumstances that the effects 

 produced by them must show, unequivocally, whether 

 the supposed operation be possible or not ; and if it be 

 found to be possible in one case, we may then argue with 

 less diffidence on the probability of its actually taking 

 place in the specific case in question. 



It has been abundantly proved by the experiments of 

 M. de Luc, and by those of my friend Sir Charles Blag- 

 den, that when water, in cooling, has arrived at the 

 temperature of about 41° F., its condensation with cold 

 ceases, and it begins to expand, and continues to expand 

 gradually as its temperature goes on to be farther dimin- 

 ished, till it is changed to ice. Availing myself of that 

 most important discovery, I made the following experi- 

 ment. 



Experiment No. 58. 



Having poured mercury, at the temperature of 60°, 

 into a common glass tumbler, till this Fluid stood at the 

 height of about an inch, I then poured about twice as 

 much water (at the same temperature) upon it ; and, 

 placing the tumbler in a shallow earthen dish, surrounded 

 it to the height of the level of the surface of the mer- 

 cury with a freezing mixture of snow and common salt. 

 Having done this, I was very curious indeed to see in 

 what part of the water ice would first make its appear- 



