388 PERU CHAP. 



reindeer lichen. In some parts it was in sufficient quantity to 

 tinge the sand, as seen from a distance, of a pale yellowish 

 colour. Farther 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 Copiapo. The appearance of the country was remarkable, 

 from being covered by a thick crust of common salt, and of a 

 stratified saliferous 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 

 saltpetre 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, employed in carrying the saltpetre, are fed. 

 The nitrate of soda was now selling at the ship's side at four- 

 teen 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 follows, for a length of 



