132 



THE ANDES OF SOUTHERN PERU 



place to place. At Arica the low coastal chain of northern Chile 

 terminates at the Morro de Arica. Thence northward is a stretch 

 of open coast, with almost no rainfall and little fog. But in the 

 stretch of coast between Mollendo and the Majes Valley a coastal 

 range again becomes prominent. Fog enshrouds the hills almost 

 daily and practically every year there is rain somewhere along 

 their western aspect. 



During the southern winter the cloud bank of the coast is best 

 developed and precipitation is greatest. At Lima, for instance, 



EASTEPLV WINDS FEEBLE 



RAINY SEASON 



SEA BREEZE 



HUMBOLDT CUBBEN 



DRY SEASON 



^ ; * — 



'■ MABITIWi COBMtLERA. 



Fig. 82 — The wet and dry seasons of 

 the Coast Range and the Cordillera are 

 complementary in time. The " wet " 

 season of the former occurs during the 

 southern winter; the cloud bank on the 

 seaward slopes of the hills is best devel- 

 oped at that time and actual rains may 

 occur. 



EASTERLY WINDS ATMGH ELEVATION 



HtlMgoLDTf.UBBtN 



DRY SEASON 



SEA BREEZE 



MUHITIMC COBPIU-EHA 



Fig. 83 — During the southern summer 

 the seaward slopes of the Coast Range are 

 comparatively clear of fog. Afternoon 

 cloudiness is characteristic of the desert 

 and increases eastward (compare Fig. 

 S6), the influence of the strong sea winds 

 as well as that of the trades (compare 

 Fig. 93B) being felt on the lower slopes 

 of the Maritime Cordillera. 



the clear skies of March and April begin to be clouded in May, and 

 the cloudiness grows until, from late June to September, the sun 

 is invisible for weeks at a time. This is the period of the garua 

 (mist) or the "tiempo de lomas," the "season of the hills," when 

 the moisture clothes them with verdure and calls thither the herds 

 of the coast valleys. 



During the southern summer on account of the greater relative 

 difference between the temperatures of land and water, the sea- 

 breeze attains its maximum strength. It then accomplishes its 

 greatest work in the desert. On the pampa of La Joya, for exam- 

 ple, the sand dunes move most rapidly in the summer. According 

 to the Peruvian Meteorological Records of the Harvard Astronom- 

 ical Observatory the average movement of the dunes from April 

 to September, 1900, was 1.4 inches per day, while during the sum- 

 mer months of the same year it was 2.7 inches. In close agree- 

 ment are the figures for the wind force, the record for which also 



