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THE POPULAR SCIENCE MONTHLY. 



shallow, containing a plastic soda-mud in the form of chloride and car- 

 bonate, deriving its carbonic acid from one source and its chlorine from 

 another during its deposition, or, subsequently, fissures were opened 



Crystal of Native Borax from Borax Lake, Natural Size. 



in the subjacent strata, allowing the escape of a limited amount of jets 

 of boracid acid from beneath in vapor, we should have all the con- 

 ditions required to account for the formation of the borax in the midst 

 of the two more loosely combined salts. 



