THE VOYAGE OF THE BEAGLE 385 



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 Co- 

 piapo. The appearance of the country was remarkable, from 

 being covered by a thick crust of common salt, and of a strat- 

 ified 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 asso- 

 ciated with much gypsum. The appearance of this super- 

 ficial 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 sur- 

 rounding 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 inhabit- 

 ants, 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 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 follows for a length of one hundred and 

 fifty miles the margin of a grand basin or plain; this, from 

 its outline, manifestly must once have been a lake, or more 

 probably an inland arm of the sea, as may be inferred from 

 the presence of iodic salts in the saline stratum. The surface 

 of the plain is 3300 feet above the Pacific. 



VOL. XXIX M HC 



