464 Of the Propagation of Heat 



Bears, wolves, foxes, hares, and other like quadrupeds, 

 inhabitants of cold countries, which do not often take 

 the water, have their fur much thicker upon their backs 

 than upon their bellies. The heated air occupying the 

 interstices of the hairs of the animal tending naturally 

 to rise upwards, in consequence of its increased elasticity, 

 would escape with much greater ease from the backs of 

 quadrupeds than from their bellies, had not Providence 

 wisely guarded against this evil by increasing the ob- 

 structions in those parts, which entangle it and confine 

 it to the body of the animal. And this, I think, 

 amounts almost to a proof of the principles assumed 

 relative to the manner in which Heat is carried off by 

 air, and the causes of the non-conducting power of air, 

 or its apparent warmth, when, being combined with 

 other bodies, it acts as a covering for confining Heat. 



The snows which cover the surface of the earth in 

 winter, in high latitudes, are doubtless designed by an 

 all-provident Creator as a garment to defend it against 

 the piercing winds from the polar regions, which prevail 

 durinor the cold season. 



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These winds, notwithstanding the vast tracts of con- 

 tinent over which they blow, retain their sharpness as 

 long as the ground they pass over is covered with snow; 

 and it is not till, meeting with the ocean, they acquire, 

 from a contact with its waters, the Heat which the snows 

 prevent their acquiring from the earth, that the edge of 

 their coldness is taken off, and they gradually die away 

 and are lost. 



The winds are always found to be much colder when 

 the ground is covered with snow than when it is bare, 

 and this extraordinary coldness is vulgarly supposed to 

 be communicated to the air by the snow ; but this is an 



