ABNORMAL CONDITIONS 229 



COMPARISON OF NORMAL AND ABNORMAL CONDITIONS 



ON THE WEST COAST 



CLIMATE 



On earlier pages, the normal wind on the west coast has been shown to be the south- 

 east trade, modified locally as a south wind, or as a sea-breeze, the virazon. These winds 

 reach a fairly high degree of saturation (80 per cent), yet as they originate from a high- 

 pressure centre, and blow from higher to lower latitude, they are essentially drying 

 winds; and as they enter the upwelling zone, condensation seldom amounts to more 

 than the production of gariia or of coastal cloud. Where the moisture capacity is in- 

 creased by the higher inland temperature, and possibly also by admixture with drier 

 inland air, the coastal cloud vanishes and the desert character of the west coast is pre- 

 served (Bowman, 19 16). The persistence for thousands of years of Chilean saltpetre 

 deposits is often cited as proof of the extreme aridity of the coastal deserts. The 

 contrast noted by Darwin (p. 109) between this and other climatic regions of South 

 America is illustrated in Plate XIV. 



Meteorological conditions reach their greatest abnormality after the summer solstice, 

 when, as pointed out on p. 205, the north-east trades enter the southern hemisphere and 

 approach the Peruvian coast as a north-west monsoon. In exceptional years these bring 

 torrential rains. On this coast rain is so seldom seen that the majority of houses, the 

 Lima cathedral included, are built of mud ; and since rivers are few and there is little 

 vegetation to hold the soil together, rains are unusually destructive. 



EL NiNO 



The Nino counter-current is shown by Schott (1931) to be a consequence of the 

 northerly winds. References to it are made on pp. 158 and 205, and we shall do no more 

 here than summarize its effects in abnormal years. In place of the cool Peru Current 

 diverging from the shore, hot poorly saline water of the Equatorial Counter-current 

 flows southwards and converges with it. The rise in temperature kills fish and plankton 

 which then decompose and emit sulphuretted hydrogen on an enormous scale. This is 

 the " Callao Painter " and it blackens the paintwork of ships lying in harbour (Raimondi, 

 1891), and on one occasion Chilean troops of occupation are said to have been called out 

 to inter miles of putrifying organisms on the beach. At the same time and no less serious, 

 the guano birds lose their food. Many die of disease and starvation, and others fly south- 

 wards in search of food, forsaking their nests and leaving the young to perish. This loss 

 to the guano industry is said to run into thousands of pounds. In abnormal years. El 

 Nino may reach as far south as Pisco, and the months of January to March are usually 

 given for its occurrence. 



AGUAJE 



Under " Irregularities of the Current", p. 216, attention has been drawn to observa- 

 tions made by Lavalle (1924) on a warm counter-current which appears off the Peruvian 

 coast from April to July, well after the retreat of El Nino. In its effects, it bears close 



16-2 



