296 SOUTH AMEEICA— THE ANDES EEGIONS. 



IV. 



Climate. 



The Peruvian climate is more temperate than might be expected from its 

 tropical position between -3° and 18° south latitude. Thanks to their great elevation, 

 the inhabited regions enjoy a temperature resembling that of the lowlands in 

 higher latitudes ; even on the coastlands in the immediate vicinity of the sea the 

 heat is lower than under corresponding latitudes elsewhere, being tempered by the 

 influence of the marine current setting steadily from the Antarctic Ocean towards 

 the equatorial waters. 



The "Humboldt Current," as this stream is called, in honour of the great 

 traveller and physicist by whom it was first observed and described, contains a 

 liquid mass some hundred miles broad and of enormous thickness. The soundings 

 of the Romanche have shown that the temperature falls rapidl}^ down to the bottom, 

 undisturbed by any counter-current of warm water. In fact, it is the lower 

 strata which, by continually returning to the surface, tend to modify the normal 

 heat of the coastlands, for they are as cold at Callao as at Valparaiso, 21° of 

 latitude farther south. Under the action of the south-east trade winds the 

 surface waters are driven seawards, while near the coast the void thus created is 

 filled by the cold layers rising from the lower depths. 



The mean temperature, which increases slowly in the equatorial regions, onl}^ 

 reaches 59° or 60° Fahr. off the coast of Lima ; hence it is some 18° below the 

 normal heat of the oceanic waters at a distance from the seaboard. Speaking 

 generally, the atmospliere above the marine current is scarcely warmer, and thus 

 refreshes by several degrees the coastlands exposed to its influence. Lima, situated 

 near 12° south latitude, a little nearer to the equator than Bahia on the opposite side 

 of the continent, enjoys a perceptibly more temperate climate.* The fogs in 

 which the maritime plains of Peru are shrouded for a great part of the year also 

 tend to temper the heats. In winter the south wind is occasionally rej)laced by 

 a northern monsoon ; which, however, never blows in high gales, so that the 

 surrounding waters remain, if not calm, at least amongst the most tranquil of the 

 " Pacific " Ocean. 



But if the Peruvian seaboard is exempt from the torrid heats of coasthmds 

 lying under the same latitude, the Andean uplands enjoy a much warmer climate 

 than might be supposed from their great altitude. In this respect the climate 

 of Peru is unparalleled in the whole world. Usually there is a fall of 1° Fahr. for 

 about 828 feet of increased altitude ; but on the Andean slopes the average is no 

 more than 1° for every 935 feet. Thus the climate of Lima is entirely local, 

 while the isothermal lines of the higher regions correspond to those of the 

 African mountains, t 



In Peru the normal trade wind, which in the torrid zone usually blows from 



* Mean temperature of Lima (12° 3' S. lat.), 67° Fahr. ; of Bahia (12° 58' S. lat.), 77° Fahr. 

 t John Ball, op. cit., p. 100. 



