CHAPTER XIV. 



TEMPERATURE AND ALTITUDES OF SNOW-FIELDS 

 AND GLACIERS. 



AT altitudes varying in different localities according to 

 their latitudes, we reach a zone of perpetual or, rather, 

 as it should be called, perennial snow. The snow-fields 

 beyond are known as nave's, while the fringe of ice begirding 

 their lower edge are known as glaciers. In Norway we 

 find both in the higher- lying plateaux, the remains, it may 

 be, of a far more extensive Arctic snow-field than that 

 which now exists in polar regions, one which, with snow 

 and ice, during what in geology is called the glacial period, 

 covered extensively the whole of Europe. 



While it is the case that difference in soil and difference 

 in atmospheric pressure at different altitudes in a moun- 

 tainous country are not to be altogether ignored in con- 

 sidering causes of the geographical distribution of plants, 

 it is chiefly as an indication of temperature at which dif- 

 ferent kinds of trees are found at different altitudes that 

 it is deemed of importance by the student of forest science. 

 In this connection the line of perpetual snow is supposed to 

 supply him with a valuable indication of a temperature 

 which never falls much below the freezing point, from 

 which he learn much by ascertaining how near to this may 

 different species of trees can grow and flourish. 



In Norway in the zones of the oak, and of the birch, and 

 of the cultivated fields, the temperature is moderate. In the 

 midland districts the cold is more severe ; but there pine 

 and fir forests of boundless extent rise on high stony 

 ranges, intersected with plains and valleys of meadow and 

 cultivated land, and dells where the willow and the alder 

 vegetate in great luxuriance. ' And here/ writes one who 



