Dr. IIolyoke's Estimate of tJie Excess of Had and Cold. 



69 



^. 



be supposed tliat tliey increase tlie cold, before that period. 

 Add to tliii^, 4th. That this surface of ice, •svhicli covers the 



lakes every winter, is pretty early in the season clothed with 

 snow, more qr less deep, as well as the whole surface of 

 these northern countries: Now, no one can suppose that 



snow, because it lies upon a surface of water or ice, is capa- 

 ble of producing a greater degree of cold in the atmosphere, 

 than if it covered an equal extent of ground. These ' obser- 

 I vations do, I think, evidently shew, that this hypothesis is 

 not admissible. 



Others have supposed, " that our woods and thick forests, 



by harbouring large quantities of snow every winter, 



and 



screening it from the action of the sun's 



rays, 



do 



occasion 



the air, which blows over it, to be much coldci', than 



it 



would be otherwise 



than it is in Europ 



This may 



indeed in some measure account for the length of our win- 



and the sharp 



of the YsindiB 



the 



sp 



as 



snow will remain longer undissolved, when shaded fr 



the 

 the 



than 



open and 



ted p 



of the country: 

 lich lies in the 



But, I do not conceive liow^ the snow, wl 



woods, should communicate any extraordinary keenness to 



the 



Taeyond that 



covers the ground 



1 



in these regions, whether cleared or imcleared, during tlie 



winter season. 



However, that the woods of America are somehow the 

 occasion of its greater cold, must, I beheve, be admitted. 

 Several writers have observed, that the winter's cold in the 



old 

 the 



formerly mucl 



] more 



severe and 



climate, aiid 



same spot, th 



ay 



#^ 



Th 



i 



