ALTITUDES OF SNOW-FIELDS AN 



parallel to the plane of perpetual snow, the intervals, 

 observed by him at Alten, being given by the following 

 table of limiting heights of vegetation above the sea : 



VEGETATION IN LATITUDE 70. 



The Pine (Pinus sylvestris) ceases at 237 metres = 780 Eng. feet. 

 The Birch (Betula alba) 482 =1580 



The Bilberry ( Vaccinium 



Myrtillus), 620 = 2030 



The Mountain Willow 



(Salixmirsinites), 656 = 2150 ,, 



The Dwarf Birch (Betula 



nana), ,, 836 = 2740 



The Snow-line, 1060 = 3480 



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 

 probable, however, that the direct sea-blast to which those 

 bare rocks are exposed, must act chemically upon vegeta- 

 tion in a way which would render the deduction of the 

 snow-line considerably doubtful which doubt is confirmed 

 by the more recent determination of the snow-line on the 

 island of Seiland, opposite to Qualoe. 



Von Buch estimates the interval between the limit of 

 the birch and perpetual snow at about 1,870 English feet 

 throughout Norway ; Wahlenberg estimates it at 1,960 

 English feet ; which probably represents best the results 

 in higher latitudes. 



And as a guide to fill up the gaps of direct observation, 

 he adds, some determination of the limit level of the 

 common birch in Norway, taken chiefly from the Goea 

 Norvegica, from Naumanris Travels, and from the obser- 

 vations of Wahlenberg and of Smith, the Norwegian 

 botanist. These he has given in tabular form, represent- 

 ing the estimated altitude of the snow-line in twelve 

 different localities, ranging from 59J to 71 2', adding to 

 the mean limit of the birch 900 feet, as the limit of the 

 birch and perpetual snow, and in six of the cases the alti- 

 tude of the observed snow-line, which shows a general 

 accordance, and, in some cases, an approximate conformity, 

 of the one with the other. 



