214 CLIMATOLOGY. 



land maintains, must find grass and lichens, whereon they 

 fatten.* 



On the north side of Lake Superior, the duration of 

 the winter's snow is less by at least sixty days than it 

 is in lat. 65° N., that being the difference due to about 

 twenty-seven degrees of latitude. In favourable seasons, 

 at Melville Island, in lat. 74f° N. and long. 110° W., 

 the snow towards the end of June lies only in the 

 valleys where it had drifted deeply, and the level mea- 

 dows remain uncovered for seventy days, or till the 

 beginning of September. In Regent's Inlet, which is 

 more to the eastward, the snow dissolves less rapidly ; 

 and at Igloolik, still further east, notwithstanding a 

 difference of 5^° of southing, the soil is uncovered for 

 a still shorter period, furnishing an illustration of the 

 depression of temperature on the eastern coasts, on which 

 some observations will be made in a subsequent page. 

 The subjoined tables will furnish the dates of the dis- 

 appearance of the snow in the spring, of various more 

 southern localities. 



The opinion held at no distant date by eminent mete- 

 orologists, that a mean annual temperature of the freez- 

 ing point of water coincides with the snow line, has been 

 satisfactorily disproved by observation. Everywhere to 

 the eastward of the Rocky Mountains, the isothermal of 

 32° F. is below the fifty-seventh parallel of latitude. 



When the rigour of the climate of Arctic America is 



* The Herald Island, discovered by Captain Kellett in lat. 71° 19' 

 N., long. 175° 23' W., to the north of Beering's Straits, is 1200 feet 

 high, and consists of granite precipices to the height of 900 feet, and 

 then a succession of terraces, on which there grows a turfy vegetation. 

 Eight species of plants were gathered from these terraces, viz. a Hepatica, 

 Poa arctica and another grass, Artemisia borealis, Cochleariafenestrata, 

 Saxifraga laurentiniana, a moss and a red lichen, which covered the 

 rocks. 



