EFFECTS OF CALORIC ON BODIES. 401 



artificial means bodies may be deprived of certain 

 portions of it ; and then the substance most usu- 

 ally contracts, and increases in weight. Water is 

 an exception to this ; for in losing a part of its 

 heat, the cause of its fluidity, and becoming ice, 

 it expands, and is rendered lighter, by enclosing, 

 during the operation, more or less of atmospheric 

 air : consequently it swims, covering the surface. To 

 this very simple circumstance, ice floating and not 

 sinking, are the banks and vicinities of all the 

 rivers, lakes, pools, or great bodies of water in 

 northern Europe, Asia, and America, rendered 

 habitable, and what are now the most fertile and 

 peopled would be the most sterile and abandoned, 

 were it not for this law of nature. Had ice 

 been so heavy as to sink in water, the surface on 

 freezing would have fallen to the bottom, and a 

 fresh surface would be presented for congelation ; 

 this would then descend in its turn, and unite with 

 the other ; and thus during a hard frost successive 

 surfaces would be presented, and fall to the bottom, 

 as long as the frost or any fluid remained. By 

 this means the whole body of the water would 

 become a dense concretion of ice : its inhabitants 

 would not only perish, but the indurated mass 

 would resist the influence of the sun of any sum- 

 mer to thaw it, and continue congealed through- 

 out the year, chilling the earth in its neighbour- 

 hood, and the winds that passed over it, preventing 



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