820 Biographical Memoir of Count Rurnford. 



precipitated to the bottom to be heated. This he verified by di- 

 rect and ingenious experiments. So long as only the upper 

 part of a column of liquid was heated, the lower part 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 bot- 

 tom, did not melt a particle of it. A bit of ice kept under boil- 

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

 in three minutes. Whenever the internal motion of a liquid 

 was arrested by the interposition of some non-conducting sub- 

 stance, the cooling 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 before freezing. It is for this reason that ice always forms 

 at the surface, and that once formed, it pi'eserves 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 pre- 

 vents 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 possesses, the reverse of that of fresh water, by 

 which, at all degrees of temperature, its molecules are precipi- 

 tated when they are cooled ; so that the ocean, being always tem- 

 perate at its surface, softens the rigour of the winters along the 

 shores, and warms again, by its currents, the polar chmates, at 

 the same time that it cools those of the equator. 



The interest of Count Ruraford's observations, therefore, ex- 

 tended, 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 public and private economy. 



Their mere announcement must have made my hearers an- 

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



