302 On the Physical Geography of Norway. 



the burning plains of Hindostan. This is chiefly due to the 

 excessive dryness of the climate of Thibet. In like manner* 

 five times less rain falls on the coast of the Baltic than at 

 Bergen. All this confirms the excellent generalization of Von 

 Buch, that it is the temperature of the summer months which 

 determines the plane of perpetual snow. It is thus easy to 

 understand why the mean temperature of the snow line dimi- 

 nishes towards the pole, because for a given mean temperature 

 of the whole year the summer is far hotter in proportion. 

 Also, places at which the temperature of the summer is low, 

 are those which have a moderated or coast climate ; but there 

 also the fall of rain and snow is most abundant, whilst in ex- 

 cessive or continental climates the precipitations are compara- 

 tively small. The red lines on the small chart which indicate 

 the mean temperature of July, have therefore a peculiar sig- 

 nificance as respects perpetual snow ; to take only one instance 

 at present, they explain why in Iceland snow lies all the year 

 at a height of only 3100 feet, whilst in Norway, on the same 

 parallel, the snow line would approach 4000. 



The same general principle holds good in the Southern 

 Hemisphere. Its temperature, on the whole, being greatly 

 inferior to that of the north (though the extremes are less), it 

 acts towards the rest of the globe in some measure as the 

 refrigeratory of a great distilling apparatus (as some one has 

 correctly observed), and its higher latitudes are the seat 

 of almost continual storms and fog, of which the climate of 

 Cape Horn is a familiar example. Summer there can hardly 

 be said to exist, and the snow line is proportionally low. Ac- 

 cording to Sir James Ross,* the first living authority on the 

 subject, the snow line does reach the level of the sea in the 

 antarctic regions, at a latitude between 67° and 71°, under 

 which forests still grow in Norway, and even corn in some 

 sheltered places. 



The following are the only estimates I have met with of 

 the level of perpetual snow in Norway, although it is pro- 

 bable that others exist. We shall commence with the south- 

 west district. 



From a private letter with which he kindly favoured 



me. 





