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 
