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 and gathers on the seaward slopes of the coastal hills as the inflowing air ascends them in its journey castward (see Fig. 19 for illustration of the general principles involved). Some- times it lies as fog on the surface of the land and the water; more frequently it is cloud that hangs some distance above them. On many parts of the coast its characteristic position is

. 19 —Topographic and climatic cross section to show varying positions (A, B, C) of the cloud bank on the seaward edge of the desert of northern Chile and Peru.

from 2000 to 4000 feet above sea level, descending at night nearly or quite to the surface, ascending by day and sometimes all but disappearing except as rain clouds on the hills, Accord- ing to Mossman, the relative humidity on the coast between latitude 18° and 30° S. rarely falls below 50 per cent. At Iquique the monthly range is 74-77 per cent.

In Peru the coastal fog is known as gartia, in Chile as caman- chaca. ‘Vhere is much variation from place to place in its position and habits. Lima, in latitude 12° S., has a great deal of fog; while Trujillo, in latitude 1o° S., has little fog and a good deal of sunshine and is distinctly warmer. Fog is char- acteristic of Antofagasta during the winter season; by con- trast it is largely absent at Iquique. Where the hills of the Coast Range are high or there is a convergence of slopes to- ward a central point the fog may thicken to an actual drizzle and determine the location of a settlement. Paposo, as we have already mentioned, has a little pasture supported chiefly by the coast fog.

Copiap6 lies within (east of) the Coast Range, and, though its elevation is but 1300 feet above the sea, it enjoys a certain protection, On the coast at Caldera, the principal port of the