chap. x. Saline Beds at Iqtiique. 303 



M. d'Orbigny, and from finding on a fresh examination 

 of this agglomerated sand, that it is . not irregularly 

 cemented, but consists of thin layers of sand of different 

 tints of colour, alternating with excessively fine paral- 

 lel layers of salt, I conclude that it is not of alluvial 

 origin. M. d'Orbigny l observed analogous saline beds 

 extending from Cobija for five degrees of latitude 

 northward, and at heights varying from 600 to 900 

 feet : from finding recent sea-shells strewed on these 

 saliferous beds, and under them, great, well-rounded 

 blocks, exactly like those on the existing beach, he 

 believes that the salt, which is invariably superficial, 

 has been left by the evaporation of the sea-water. This 

 same conclusion must, I now believe, be extended to 

 the superficial saliferous beds of Iquique, though they 

 stand about 3,000 feet above the level of the sea. 



Associated with the salt in the superficial beds, 

 there are numerous, thin, horizoutal layers of impure, 

 dirty- white, friable, gypseous and calcareous tufts. The 

 gypseous beds are very remarkable, from abounding 

 with, so as sometimes to be almost composed of, irregu- 

 lar concretions, from the size of an egg to that of a 

 man's head, of very hard, compact, heavy gypsum, in 

 the form of anhydrite. This gypsum contains some 

 foreign particles of stone ; it is stained, judging from 

 its action with borax, with iron, and it exhales a strong 

 aluminous odour. The surfaces of the concretions are 



1 ' Voyage,' &c. p. 102. M. d'Orbigny found this deposit inter- 

 sected, in many places, by deep ravines, in which there was no salt. 

 Streams must once, though historically unknown, have flowed in 

 them; and M. d'Orbigny argues from the presence of undissolved 

 salt over the whole surrounding country, that the streams must have 

 arisen from rain or snow having fallen, not in the adjoining country, 

 but on the now arid Cordillera. I may remark, that from having 

 observed ruins of Indian buildings in absolutely sterile parts of the 

 Chilian Cordillera (' Journal,' 2nd edit. p. 357), I am led to believe 

 that the climate, at a time when Indian man inhabited this part of 

 the continent, was in some slight degree more humid than it is at 

 present. 



