Ch. XIII.] 



COVERING OY SNOW AND ICE. 



285 



n 



time 



area ana enaurmg iui <* xung^* ^— ? 



preventing loss by radiation, snow being a very bad con- 



ductor of heat. 



New 



meado 



wind having blown away its snow, are often frozen for a depth 

 of two feet or more, so that when spring returns this portion 



remains 



heat. 



field is green and clothed with a rapidly growing vegetation 

 a check having been given by the snow to the radiation of 



Dr. Hooker found in like manner that, after the melting 

 , snow on the Himalaya, the warmth of the soil was far 

 above the mean temperature of the region, owing to the same 

 cause. In this way there may be some compensation the 

 excess of heat absorbed by the land, during a short but hot 



summer 

 snow. 



, being less ireeiy paaueu. wj.^ **- 



This loss by radiation during a protracted winter, is 

 only one of many elements as yet undetermined which com- 

 plicate the problem on which we are now speculating. 



Quantity of polar ice and its influence in altenng the level oj 

 the ocean.-Among other data respecting which we require 

 accurate information, and which at present the meteorologist 

 cannot supply, is the quantity of ice now resting on land 

 above the sea-level in the arctic and antarctic zones. Ante- 

 cedently to experience it might have been thought that the 

 thickness of the ice would increase as it extended northwards ; 



i— x -r,_ ^o+ori within about seven degrees, and Kane 



North Pole, and they both of them 



Zn7open7e & a there, though they had reached a latitude so 

 much higher than that in which the continent of Greenland 

 is enveloped in a winding-sheet of perpetual snow. ^ 



- - • i earn that, although m the 



From 



st may i« 

 mountain 



may have been buried 



much 



vasx covering ui x^c, j^" —~ 



higher latitudes may not at the same period have been frozen. 

 wo o^ Tw no means called upon as geologists to embrace 



We are by no means 



embrace 

 from 



temperate 



the pole to lat. 50°, still less to 40° in the 



It has long been a favourite opinion of northern voyagers that 



