642 THE POPULAR SCIENCE MONTHLY. 



contained in the sedimentary beds originated chiefly from the 

 interior reservoirs of the globe, whence it has also been brought 

 by the agency of thermal springs. This is illustrated in the im- 

 portant beds of Estremadura, where phosphorite associated with 

 quartz constitutes numerous vertical veins, which have been filled 

 up from below. Incidentally, the substance has penetrated the 

 calcareous strata, and has assumed the forms of fossils within 

 them, thus bringing a new proof of aqueous precipitation. 



Still more frequently than any other substance, is quartz dis- 

 tributed in large veins. The granitic plateau of France, Brittany, 

 the Vosges, and the Pyrenees presents numerous examples of it. 

 These veins can often be perceived from a considerable distance. 

 Besides crystallized quartz, they frequently contain parcels of 

 metalliferous minerals, and thus represent transitions toward 

 metalliferous veins proper. The ribboned texture of chalcedony 

 and agate, which abound in these veins, and the manner in which 

 they are related to deposits of precisely the same nature, inclosed 

 in adjoining strata, confirm the view of their aqueous origin and 

 permit their age to be determined. This is exemplified in the 

 department of the Loire, where these veins are thus associated 

 with porphyry, and at the northern point of Morvan ; and in the 

 remarkable quartz-veins of the Sierra Nevada, in California, 

 which are auriferous at some points." Comprised within a zone 

 some nine or ten miles wide, they extend from north to south 

 along the chain for nearly two hundred miles. One of the most 

 considerable of these, " the great quartz-vein," can be followed 

 over more than thirty-five miles. 



In fact, all these outflowings of quartz and connected min- 

 erals, whatever may be the diversity of their forms, in veins, 

 masses, or strata, attest, not less authentically than the metallifer- 

 ous beds, the intervention and generative power of subterranean 

 waters which have been long since exhausted. We shall next see 

 that waters sufficiently superheated deposit as quartz-crystal the 

 silica which they hold in solution. It is thus explained how this 

 mineral has in a certain way become the binder-up of the fractures 

 of the terrestrial crust. — Translated for the Popular Science 

 Monthly from the Revue des Deux Mondes. 



A CONNECTION may be hypotlietically traced between the frequent earthquakes 

 in South America and certain subsidences which appear to be going on in the 

 Andes. The city of Quito has sunk 26 feet in 122 years ; the farm of Antisana — 

 the highest inhabited spot on the globe — 165 feet in 64 years ; and the peak of 

 Pichincha 218 feet in 122 years. The squeezing of the crust of the earth which 

 is produced by such sinking of the masses of these ranges must produce violent 

 dislocations in the surrounding regions ; and these are the terrible earthquakes 

 which we witness. 



