306 On the Physical Geography of Norway. 



VEGETATION IN LATITUDE 70°. 



The Pine (Pinus sylvestris) ceases at 

 The Birch (Betula alba) ceases at . 

 Bilberry ( Vacciniutn Myrtillus) ceases at 

 Mountain Willow (Salix Myrsinites) ceases at 

 Dwarf Birch {Betula nana) ceases at 

 The Snow line ..... 



237 metres = 780 Eng. ft. 

 482 metres = 1580 Eng. ft. 

 620 metres = 2030 Eng. ft. 

 656 metres = 2150 Eng. ft. 

 836 metres = 2740 Eng. ft. 

 1060 metres = 3180 Eng. ft. 



From the growth of the birch he has estimated the level 

 of the snow line in the islands of Qualoe and Mageroe, 

 though neither of these rise to the requisite limit. It is pro- 

 bable, however, that the direct sea blast to which those bare 

 rocks are exposed must act chemically upon vegetation in a 

 way which would render the deduction of the snow line con- 

 siderably doubtful — which doubt is confirmed by the more 

 recent determination of the snow line on the island of Sei- 

 land, opposite to Qualoe. Still, as a guide to fill up the gaps 

 of direct observation, I add some determinations of the limit- 

 level of the common birch in Norway, chiefly taken from the 

 Gaia Norvegica, from Naumann's Travels, and from the 

 observations of Wahlenberg, and of Smith the Norwegian 

 botanist. These are important, as indicating the law of the 

 phenomenon. Von Buch estimates the interval between the 

 limit of the birch and perpetual snow at about 1870 English 

 feet throughout Norway ; Wahlenberg, at 1960 English feet ; 

 which probably represents best the results in higher latitudes. 

 In the following table, I have inferred the height of the snow 

 line from the limit of the birch, by adding 1900 feet to the 

 latter number ; and I have added in another column the direct 

 determinations of the snow level previously given. 



