364 PERU. [chap. xvi. 



unattached. This plant belongs to the genus Cladonia, and some- 

 what resembles the reindeer lichen. In some parts it was in suf- 

 ficient quantity to tinge the sand, as seen from a distance, of a 

 pale yellowish colour. Further inland, during the whole ride of 

 fourteen leagues, I saw only one other vegetable production, and 

 that was a most minute yellow lichen, growing on the bones of 

 the dead mules. This was the first true desert which I had seen : 

 the effect on me was not impressive ; but I believe this was owing 

 to my having become gradually accustomed to such scenes, as I 

 rode northward from Valparaiso, through Coquimbo, to Copiap6. 

 The appearance of the country was remarkable, from being co- 

 vered by a thick crust of common salt, and of a stratified salife- 

 rous alluvium, which seems to have been deposited as the land 

 slowly rose above the level of the sea. The salt is white, very 

 hard, and compact : it occurs in water-worn nodules projecting 

 from the agglutinated sand, and is associated with much gypsum. 

 The appearance of this superficial mass very closely resembled 

 that of a country after snow, before the last dirty patches are 

 thawed. The existence of this crust of a soluble substance over 

 the whole face of the country, shows how extraordinarily dry the 

 climate must have been for a long period. 



At night I slept at the house of the owner of one of the salt- 

 petre mines. The country is here as unproductive as near the 

 coast ; but water, having rather a bitter and brackish taste, can 

 be procured by digging wells. The well at this house was thirty- 

 six yards deep : as scarcely any rain falls, it is evident the water 

 is not thus derived ; indeed if it were, it could not fail to be as 

 salt as brine, for the whole surrounding country is incrusted with 

 various saline substances. We must therefore conclude that it 

 percolates under ground from the Cordillera, though distant 

 many leagues. In that direction there are a few small villages, 

 where the inhabitants, having more water, are enabled to irrigate 

 a little land, and raise hay, on which the mules and asses, em- 

 ployed in carrying the saltpetre, are fed. The nitrate of soda 

 was now selling at the ship's side at fourteen shillings per hundred 

 pounds : the chief expense is its transport to the sea-coast. The 

 mine consists of a hard stratum, between two and three feet thick, 

 of the nitrate mingled with a little of the sulphate of soda and a good 

 deal of common salt. It lies close beneath the surface, and fol- 



