CLIMATOLOGY OF THE. PERUVIAN ANDES 145 



colors between sky and sea. It is impossible not to be profoundly 

 moved by so majestic a scene. A long resplendent path of light 

 upon the water is reflected in the clouds. Each cloud -margin is 

 tinged with red and, as the sun sinks, the long parallel bands of 

 light are shortened westward, changing in color as they go, until 

 at last the full glory, of the sunset is. concentrated in a blazing arc 

 of reds, yellows, and purples, that to most people quite atones for 

 the dull gray day. and its humid air. 



At times the clouds are broken, up by the winds and scattered 

 helter-skelter through the west. A few of them may stray into 

 the path of the sun temporarily to hide it and to reflect its pri- 

 mary colors when the. suni reappears. From the main cloud masses 

 there reach out slender wind-blown streamers, each one delicately 

 lighted as the sun's rays filter through its minute water particles. 

 Many streamers are visible for only a short distance, but when 

 the sun catches them their filmy invisible fingers become delicate 

 bands of light, some of which rapidly grow out almost to the dome 

 of the sky. Slowly they retreat and again disappear as the rays 

 of the sun are gradually shut off by the upturning curve of the 

 earth. 



The unequal distribution of precipitation in the climatic zones 

 of western Peru has important hydrographic consequences. These 

 will now be considered. In the preceding figure four types of 

 stream profiles are displayed and each has its particular relation 

 to the cloud bank. Stream 1 is formed wholly upon the coastal 

 terraces beneath the cloud bank. It came into existence only 

 after the uplift of the earth 's crust that brought the wave-cut plat- 

 forms above sea level. It is extremely youthful and on account 

 first of the small seepage at its headquarters — it is elsewhere 

 wholly without a tributary water supply — and, second, of the re- 

 sistant granite that occurs along this part of the coast, it has very 

 steep and irregular walls and an ungraded floor. Many of these 

 "quebradas" are difficult to cross. A few of them have fences 

 built across their floors to prevent the escape of cattle and burros 

 that wander down from the grassy hills into the desert zone. 

 Others are partitioned off into corrals by stone fences, the steep 



