CLIMATOLOGY OF THE PERUVIAN ANDES 147 



masses in the path of the stream. Here and there are villages. 

 The streams have fish. When the water rises the river may be 

 unfordable and people on opposite sides must resort to boats or 

 rafts. 4 



EASTERN BORDER CLIMATES 



On windward mountain slopes there is always a belt of maxi- 

 mum precipitation whose elevation and width vary with the 

 strength of the wind, with the temperature, and with the topog- 

 raphy. A strong and constant wind will produce a much more 

 marked concentration of the rainfall. The belt is at a low eleva- 

 tion in high latitudes and at a high elevation in low latitudes, with 

 many irregularities of position dependent upon the local and espe- 

 cially the minimum winter temperature. The topographic con- 

 trols are important, since the rain-compelling elevation may scat- 

 ter widely the localities of maximum precipitation or concentrate 

 them within extremely narrow limits. The human effects of these 

 climatic conditions are manifold. Wherever the heaviest rains 

 are, there, too, as a rule, are the densest forests and often the 

 most valuable kinds of trees. If the general climate be favorable 

 and the region lie near dense and advanced populations, exploita- 

 tion of the forest and progress of the people will go hand in hand. 

 If the region be remote and some or all of the people in a primi- 

 tive state, the forest may hinder communication and retard devel- 

 opment, especially if it lie in a hot zone where the natural growth 

 of population is slow. . . . These are some of the considerations 

 we shall keep in mind while investigating the climate of the east- 

 ern border of the Peruvian Andes. 



The belt of maximum precipitation on the eastern border of 

 the Andean Cordillera in Peru lies between 4,000 and 10,000 feet. 

 Judging by the temporary records of the expedition and especially 



4 In most of the coast towns the ford or ferry is an important institution and the 

 chimbadores or taleadores as they are called are expert at their trade: they know 

 the regime of the rivers to a nicety. Several settlements owe their origin to the 

 exigencies of transportation, permanent and periodic; thus before the development of 

 its irrigation system Camana, according to General Miller (Memoirs, London, 1829, 

 Vol. 2, p. 27 ) , was a hamlet of some 30 people who gained their livelihood through 

 ferrying freight and passengers across the Majes River. 



