298 SOUTH AMERICA— TUE ANDES EEGIONS. 



tiie sea-breezes, which are too dry to precipitate any moisture on the plains, at 

 times discharge torrents on the higher slopes, where the pressure of the aerial 

 masses extracts the rain as from a vast sponge. During these sudden downpours 

 the porous and friable clays on the slopes are transformed to huge masses of mud, 

 which rush like avalanches down to the gorges, where tliey move steadily forward, 

 absorbing the lateral rivulets, and sweeping away the trees, plantations and houses 

 along their passage. 



For six months, from April to October, a moist tepid fog hangs over the low- 

 Ij'ing Peruvian coastlands, especially in the Lima district. Towards October and 

 November the vapours lift and become light enough to admit the solar rays. At 

 times, particularly in August, the essentially foggy month, it is dense enough to 

 precipitate a kind of dew, locally called gariia, which farther inland is replaced by 

 rain. Tschudi mentions certain plantations where the gariia and rainy zones are 

 separated by a single wall. 



The general lack of moisture facilitates the development of saline efflorescences 

 wherever the air is too dry even to form dews. South Peru, though in a less 

 degree than in the provinces lately annexed to Chili, abounds in chemical 

 substances, such as gypsum, salts and nitre, and deposits of cadti, or native salt, 

 occur in every part of the country, even on the inter-Andean plateau, associated 

 in many districts with layers of caUche, or nitrate of soda. Certain coastlands 

 might be compared to flights of marble steps, being disposed in successive terraces 

 covered with white saline particles. To the same absence of moisture must be 

 attributed the formation of the guano -beds, which were formerly so valuable, and 

 which could never accumulate in regions enjoying even a moderate rainfall.* 



Y. 



Flora. 



The Peruvian flora, varying with the climate, is represented on the rocky and 

 argillaceous coastlands by a few grey plants and open scrub ; by a richer and 

 greener vegetation on the western slopes exposed to damp fogs and even rains ; by 

 a great variety of species in the inter- Andean regions, but diminishing in number 

 and size with the altitude ; lastly by a boundless exuberance of growth on the 

 Montana, where nature reveals herself in thousands of forms not yet fully known 

 to science. As elsewhere in the Andean regions, the botanical zones are super- 

 imposed, but with a few overlappings due to local contrasts of soil and climate. 



Amongst the native species the order of compositoe is best represented, 

 especially by the sunflowers, a family characteristic of the New World ; in some 



* Meteorological conditions of some Peruvian cities : — 



Altitude. 

 Latitude. Feet. 



Lima . . . 12° S . 544 



Arequipa . . 16" 24' 6,650 



Cuzco . . , 13^30' 11,390 



CerrodePaeco . ICôô' 14,280 



