312 Dr. Carl Ochsenhis — On Metalliferous Depodts. 



they are the least soluble of the sea-salts, still remain in the mother 

 liquor, and their prominent presence in any form enables geologists 

 clearly to distinguish mother liquor from ocean water, even when in 

 a concentrated state. Now, as the formation of rock-salt can only 

 occur on the coasts, and as the volcanic action of our earth takes 

 jilace also on coasts or in regions adjacent, it follows that upheavals 

 of rock-salt layers, with quantities of mother liquor in the de- 

 pressions of the anhydrite, must have been of frequent occurrence. 

 From these considerations a very simple explanation is found of 

 those phenomena which are clearly the result of marine salts in 

 solution, but which cannot possibly have resulted from a direct 

 covering of the sea, and which cannot be connected with the 

 operation of even concentrated ocean water with its contents of 

 ordinary marine salts and organic beings. Such a phenomenon is 

 seen in the formation of the nitrate of soda beds of Tarapaca and 

 Atacama in So-uth America. The enormous salt wealth of the Andes 

 is well known ; there the mother liquors carried up with the salt 

 layers ultimately forced their way down the mountain slopes, either 

 over or underground, eastward and westward into the lower levels 

 on their way to the sea, leaving evidence of their passage in 

 metalliferous veins in the form of chloride, bromide, and iodide of 

 silver, etc. ; in Tarapaca and Atacama, however, the Coast Cordil- 

 leras, composed of granite and mica schist, stopped their course, and 

 the mother liquors, having been subject to the action of volcanic 

 carbonic acid, became partially transformed into carbonate of sodium, 

 and the latter, coming into contact with guano dust, carried inland 

 from the coast by the strong predominant westerly winds, furnished 

 the material for the formation of nitrate of sodium, the beds of 

 which contain, and contain exclusively, the characteristic mother 

 liquor salts or their immediate derivates. An intelligible explanation 

 is thus given of the enormous altitude of some of the nitrate of 

 soda fields (Maricunga upwards of 4000 m. above the level of the 

 sea), of the want of uniformity in the different salt beds; of the 

 common prevalence of the borates ; the total absence of fossils ; 

 the preponderance of phosphates in the coast guano south of Arica 

 as against the absence of phosphates in the guano of the interior of 

 the provinces of Tarapaca and Atacama ; and the consequent absence 

 of phosphoric acid in the nitrate of soda, the nitric acid of which 

 is supplied by light phosphorless guano dust. Eastward of the 

 Andes (in the Argentine Eepublic) mother liquor salts are found as 

 salt-swamps. "With reference to the formation of the carbonate of 

 soda, it must be further remarked that such a product is only found 

 where inorganic carbonic acid has come into contact with mother 

 liquor salts ; the effects of which are to be observed on a large scale 

 in the west of the United States. 



As to this it was stated before the same society in my treatise : 

 " Geologisches und Montanistisches aus Utah." In addition to the 

 foregoing remarks upon the thermal and salt springs of Utah, some 

 observations upon carbonate of soda must be made, as the absence of 

 this salt in Utah throws great light upon its genesis. The report 



