264 STUDIES FOR STUDENTS 



forty inches of rain per year, distributed, however, rather uniformly 

 through tlie seasons. Where the cold is prolonged and intense, how- 

 ever, as found over the tundras within the Arctic Circle, a fifth class, 

 that of the frigid climates, may be considered. 



EFFECTS OF CONSTANTLY RAINY CLIMATES 



Constantly rainy climates are defined by W. Koppen as those 

 where no month has less than fifteen rainy days.' vSuch climates are 

 dominant south of south lat. 45°, touching southwestern Patagonia, 

 Tierra del Fuego, and southern New Zealand. xA.nother large area 

 exists in the North Atlantic, touching Iceland and approaching the 

 shores of Ireland, Scotland, and Norway. Certain tropical areas 

 also have nearly constantly rainy climates, at least six days in every 

 month being rainy, the northern half of the basin of the Amazon being 

 the most notable from the present point of view. In such regions the 

 forest vegetation attains its maximum development, the cooler parts 

 of the temperate zones hardly lagging behind the most favored tropics 

 in luxuriance, provided that the winter winds are moist, the soil and 

 antecedent vegetation have been spared by glaciation, and the more 

 recent forests by man. On the southwestern side of Patagonia, for 

 instance, in south lat. 55°, Hatcher speaks of a vegetation so profuse 

 as to suggest that he had been transported into the midst of some tropi- 

 cal jungle.^ Dusen states also that in the interior of Tierra del Fuego, 

 near the harbor of Puerto Angosta, the typical virgin forest reminded 

 him of the West African virgin forests which he had seen.^ 



In this connection the observations of Darwin upon the forests of 

 Tierra del Fuego are significant. He mentions the thick bed of 

 swampy peat covering the steep slopes above the timber line while 

 of the almost impenetrable forest below he states : 



In the valleys it was scarcely possible to crawl along, they were so completely 

 barricaded by great mouldering trunks, which had fallen down in every direc- 

 tion. When passing over these natural bridges, one's course was often arrested 

 by sinking knee-deep into the rotten wood; at other times when attempting to 

 lean against a firm tree, one was startled by finding a mass of decayed matter ready 



1 Bartholomew's Physical Atlas, Vol. Ill, 1899, Plate XIX. 



2 Princeton Patagonia Expeditions, Vol. I, 1903, p. 150. 



3 P. Dusen, "Ueber die Vegetation der feuerlandischen Inselgruppe," Englers 

 Jahrbiicher, Band XXIV, 1898. 



