33 Biographical Memoir of Count Rumford. 



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commences below, the warm molecules, becoming lighter, ascend and 

 the cold molecules are precipitated to the bottom to be heated. This 

 he verified by direct and ingenious experiments. So long as only 

 the upper part of the column of liquid was heated, the lower did 

 not in any degree partake of the heat. A piece of red hot iron 

 plunged in oil to a short distance from a bit of ice which lay at the 

 bottom, did not melt a particle of it. A bit of ice kept under boiling 

 water was two hours in melting, while at the surface it melted in 

 three minutes. Whenever the internal motion of a liquid was arrest- 

 ed by the interposition of some non-conducting substance, the cool- 

 ing or heating, in a word, the equilibrium, was retarded in it. Thus 

 feathers or hair would produce the same effects in water as in air. 



As it is known that fresh water is at its maximum of density at 

 seven degrees above the freezing point, it becomes lighter a little be- 

 fore freezing. It is for this reason that ice always forms at the sur- 

 face, and that once formed, it preserves the water which it covers. 

 Count Rumford found in this property the means by which nature 

 preserves a little fluidity and life in the countries of the north ; for, if 

 the communication of heat and cold took place in fluids as in solids, 

 or only in fresh water as in other liquids, the streams and lakes would 

 .quickly be frozen to the bottom. 



Snow, on account of the air which is mingled with it, was, in his 

 eyes, the mantle which covers the earth in winter, and prevents it 

 from losing all its heat. He saw in all this distinct precautions of 

 Providence. He saw the same in the property which salt water pos- 

 sesses, the reverse of that of fresh water, by which, at all degrees 

 of temperature, its molecules are precipitated when they are cooled ; 

 so that the ocean, being always temperate at its surface, softens the 

 rigor of the winters along the shores, and warms again, by its cur- 

 rents, the polar climates, at the same time that it cools those of the 

 equator. 



The interest of Count Rumford's observations, therefore, exten- 

 ded, in some measure, to the whole economy of nature in our 

 globe, and perhaps he made as many cases of those relations to them 

 which he perceived in general philosophy, as of their utility in pub- 

 lic and private economy. 



Their mere announcement must have made my hearers anticipate 

 this utility ; and, besides, there is no one who does not know their 

 effects from experience. It was by a regular application to these 



discoveries, that Count Rumford construct I fire-places, furnaces, 



