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PROCEEDINGS OE THE GEOLOGICAL SOCIETY. 



[Nov. 21, 



Water 



Organic matter 



Chloride of ammonium 

 Phosphate of lime . . . 



Sulphate of lime 



Chloride of sodium . . . 

 Sand 



12-45 

 17-48 

 30-20 

 10-00 



0- 80 

 16-03 



1- 60 



98-56 



From the above results it is evident that this substance had been 

 produced by the action of sea- water, probably thrown up in the form 

 of spray, on the guano-beds. The amount of ammonia contained in 

 this material being much greater than in the unaltered guano itself, 

 this substance, formerly thrown aside as worthless, is now exported 

 in large quantities, under the name of " Huano petrificado," realizing 

 a price considerably higher than the guano with which it occurs. 

 The low elevation of these guano-deposits above the present sea-level, 

 and their thickness, which is frequently not less than 10 to 15 feet, 

 sufficiently prove that, in parts at least, they are of later origin than 

 the shell-beds previously described. Other similar guano-deposits 

 are met with at Mexillones, Algodon Bay, the newly discovered San 

 Felipe Islands, and at various parts along the coast. 



At several places along the coast the raised beaches are strongly 

 impregnated with salt, which occurs both in the form of small layers, 

 or imbedded, as well as irregularly distributed in the diluvial detritus. 

 This is the case at Molle, Ceremono, and Patillos, all to the south of 

 Iquique, and several other places. These saline deposits are found 

 at the height of from 10 to 40 feet above the present sea-level ; at 

 the two first- mentioned places the salt is so abundant that cargoes 

 have occasionally been shipped from them. On the top of the Morro 

 de Arica, a hill about 500 feet above the sea, small superficial layers 

 of tolerably pure salt, from | in. to 3 inches in thickness, are also 

 met with ; and the fissures on the side of the same hill are often found 

 to be filled with veins of salt. 



At Arica I was not successful in finding Balani and Milleporce 

 attached to the sides of the " Morro " hill, as described by Lieutenant 

 Freyer* ; and the many loose sea-shells met with on the sides and 

 summit of the same I believe to have been brought there by the nu- 

 merous sea-birds, probably assisted, on the south slope, by the action 

 of the winds and shifting sands. 



That no very perceptible elevation has taken place in the imme- 

 diate neighbourhood of the Morro of Arica (or, if such an elevation 

 had taken place, that it has been followed by a subsequent depression 

 to nearly the same level) during the last 350 years, or since the 

 Spanish conquest, appears from the numerous Indian tumuli found 

 along the beach, for miles south of the Morro ; many of these are not 

 20 feet, and some probably considerably less, above the present 

 sea-level. That these tumuli have not been constructed since the 



* Darwin's ' Geology of South America,' p. 47. 



