330 



Prof. Frankland on the Physical Cause 



rays of summer to melt it. I have also seen in the Sor Fjord, 

 under similar abnormal conditions, a mass of snow lying early 

 in August last, within 10 feet of the level of the sea, although 

 the normal snow-line is there at least 4500 feet above the sea- 

 level. Mr. Hopkins calculates that the snow-line near the equa- 

 tor is 1000 feet lower than the mean line of 32°, whilst in the 

 Alps and at the Arctic Circle it is respectively 2000 and 3500 

 feet higher than the line of 32°. Hence by the influences above 

 mentioned, the snow-line at the equator is brought down no less 

 than 4500 feet below its thermal position at the Arctic Circle ; 

 and therefore, with the equatorial precipitation, and a more 

 equable temperature than at present, the snow-line in Norway 

 would descend to the sea at the Arctic Circle from its present 

 position of between 3000 and 4000 feet above the ocean. This 

 essential dependence of the height of the snow-line upon the 

 amount of precipitation and equable temperature is also con- 

 firmed by its comparative height on the coast and in the interior 

 of the Scandinavian peninsula, as given by Forbes in the follow- 

 ing Table, compiled partly from his own observations, and partly 

 from those of Von Buch, Naumann, and others* : — 



Latitude. 



Height of snow-line in feet. 



Interior. 



Coast. 



Difference. 



o 



60 

 62 

 64 

 66 



68 

 70 



5500 

 5200 

 4200 

 3700 

 3450 

 3350 



4450 

 4150 

 3650 

 3250 

 3000 

 2900 



1050 

 1050 

 550 

 450 

 450 

 450 



Thus the difference between the height of the snow-line near 

 the coast, where, owing to the impact of the Gulf-stream, the 

 winter is mild but the atmospheric precipitation great, and in 

 the interior, where the climate is one of extremes, and the air is 

 comparatively dry, amounts in some cases to as much as 1050 

 feet, or nearly one-fourth of the total height. Nor must it be 

 forgotten, in connexion with this depression of the snow-line, 

 that copious precipitation is altogether incompatible with great 

 summer heat. The incessantly clouded sky cuts off the solar 

 rays and moderates the summer temperature. It is a trite 

 observation, that a wet summer is always a cold one. 



Whilst, therefore, the tendency of augmented oceanic warmth 

 would be to raise the mean temperature of the limit of per- 

 petual snow, there would nevertheless be, within certain limits, a 



* Norway and its Glaciers, p. 214. 



