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 over broad tracts of land and sea. While we have a cold current along the entire west coast of South America as far north as Ecuador, and while the interplay between the cold current and the warm land has the general effect of causing a cloud bank to form over the coast, the position of the cloud bank, its density, whether or not it produces rain, are under at least the partial control of still greater forces relating to the broad outlines of the cordillera on the east and to the habits of the wind and rain belts in the terrestrial system.

It is only as we go north along the coastal belt of Peru that we find the belt of cloud and of slight precipitation on the sea- ward slopes of the Coast Range to have any influence upon sct- tlement and economic life. Even there the fogs and rains support too thin and narrow a belt of grass to form the basis of an important pastoral industry. For that the rainfall would have to be more regular in occurrence and distributed over a broader belt of country. Coming irregularly the rains furnish abundant pasture in one year and fail altogether the next, so that the pastures dry up and the herds must be driven down into the valleys. When the rains come their effect is truly amazing and appears the more striking because of the extreme aridity of the country to castward.

By good fortune I traveled through a part of the coastal belt of Peru during a period of rain and witnessed the delightful change of scene on passing from the burning desert into the belt of cloud. I repeat here the description of that experience already published in “The Andes of Southern Peru.”

During the winter the desert traveler finds the air tempera- ture rising to uncomfortable levels. Vegetation of any sort may be completely lacking. As he approaches the leeward slope of the Coast Range, a cloud mantle full of refreshing