ISil.] Limits of perpetual Snow in the NorfJ.. 341 



English feet. 



Scotch fir {pinus sijlvestris) 778 



Birch {hetula alha) 1580 



BWherry {vacciimimmyrtillus) 2033 



Sallx tnyrsenites 2152 



The sal'u lanata goes higher, and reaches ahiiost to the snow 

 line. 



English feet. 



Dwarf birch {hetula nana) 2745 



Snow line 35 J 7 



Hence the perpendicular distance between these respective 

 heights is as follows : 



Eiig. feet. 



From the place where the Scotch firs disappear to the 7 g^^ 



line of birches j 



From the line of birches to that of dwarf birches 1165 



From the line of dwarf birches to the snow line 77^ 



Distance of the Scotch firs from the snow line 2739 



Ditto of tlie birclies 1 937 



The same distances exist in everj' part of the Norwegian coast. 

 If the line of firs be elevated to the height of 3000 feet, then the 

 birches rise to 3802 feet, and the snow line is situated at an eleva- 

 tion of 5739 feet. The sam« diiferences probably exist over the 

 whole surface of the earth. Hence it is not the soil which occa- 

 sions these lines of elevation, but tlie temperature ; and it deter- 

 mines it with such precision, that we cannot without admiration 

 observe upon so many mountains of this coast, how the spruce firs, 

 the Scotch firs, and the birch, appear to be cut off by a determinate 

 horizontal line. They have reached the medium temperature of 

 tlieir growtli, and it is not permitted them to ascend higher. 



This would furnish us with an excellent method of determining 

 the snow line directly, even when it is not in our power to ascend 

 so high up into the atmospliere, if it were not that the growth and 

 flourishing of trees in many cases depend more upon the length and 

 intensity of the summer, than upon the mean temperature of the 

 place. If it were not for this difliculty, a single moderately high 

 mountain would enable us to determine the height of the snow line 

 in any country. A mountain from which the laurels and cypresses 

 had disappeared, would enable us to determine how far we must 

 ascend to reach the line of chesnuts, then that of filberts, beeches, 

 oaks, spruce firs, Scotch firs, birches, and last of all the snow 

 line. In this manner we might ])y immediate observations deter- 

 mine the curve of the snow line in various meridians, and finally 

 establish the law of the variation of temperature over the whole 

 surface of the earth. 



V. 



Almost a degree north from Allen, and just in the neighbour- 

 Iio(m1 of the great Ocean, lies llavimerj'est, upon the island Qaalue, 

 at the north end of Altcnfiord, the farthest north town in the world. 



