Note 322 — Chapter LIX

Nearly all travellers, from Cieza de Leon downwards, who have been on the west coast of South America, have had something to say concerning the rainless region of Peru: but “the natural reasons for these things,” for which our author asks, are given in the most agreeable form in Captain Maury’s charming book. “Though the Peruvian shores are on the verge of the great South Sea boiler, yet it never rains there. The reason is plain. The south-east trade winds in the Atlantic ocean strike the water on the coast of Africa. They blow obliquely across the ocean until they reach the coast of Brazil. By this time they are heavily laden with vapour, which they continue to bear along across the continent, depositing it as they go, and supplying with it the sources of the Rio de la Plata and the southern tributaries of the Amazon. Finally they reach the snow capped Andes, and here is wrung from them the last particle of moisture that the very low temperature can extract. Reaching the summit of that range, they now tumble down as cool and dry winds on the Pacific slopes beyond. Meeting with no evaporating surface, and with no temperature colder than that to which they are subjected on the mountain tops, they reach the ocean before they again become charged with fresh vapour, and before, therefore, they have any which the Peruvian climate can extract. The last they had to spare was deposited as snow on the tops of the Cordilleras, to feed mountain streams under the heat of the sun, and irrigate the valleys on the western slopes.” Physical Geography of the Sea, para. 195. See also Acosta’s way of accounting for the absence of rain on the Peruvian coast, in his Historia Natural y Moral de las Indias, A.D. 1608, lib. iii, cap. 23.