UNDERGROUND WATERS AND MINERAL VEINS. 635 



mineral is subject to a special influence from its particular 

 planet." TKus, in a little work of only a few pages, and ■whicli 

 was simi^ly intended to give the most necessary knowledge to the 

 practical miner, was placed for the same consideration of utility 

 as determines the employment of the compass, the notion of this 

 pretended affinity between the metals and the planets. 



The mode of formation, or, as Buff on said, the genesis of miner- 

 als is one of the most interesting questions of their history. But 

 the problem could not be approached until geologists had fur- 

 nished precise data on the conditions of their bearing. Satis- 

 factory solutions have recently been obtained in the case of a cer- 

 tain number of mineral species. Synthetic experiment, placing 

 itself in the circumstances that seem to have presided at their 

 formation, has succeeded in reproducing them, with their crystal- 

 line forms, and all their essential characteristics, and has thus 

 completed the demonstration of their origin. By means of this 

 method of demonstration, we have been able to ascertain that 

 many minerals are due to the action of subterranean waters. From 

 the most ancient epochs, these waters have circulated through the 

 crust of the earth, where they have left, at a multitude of points, 

 signs revealing the part they have played, and the course they 

 have taken, even more clearly than contemporary phenomena 

 •have done. 



The sedimentary beds, formed like the deposits which the sea 

 spreads every day in the bottom of its basin, are often distin- 

 guishable from one another, even at first sight, by certain exterior 

 characters. The differences are, for the most part, produced by 

 the action of subterranean waters, as is demonstrated by the ani- 

 mal and vegetable fossils, which were for a long time designated 

 as petrifactions, or, rather, by the chemical changes which these 

 fossilized bodies have evidently undergone. 



Here, shells and corals, showing forms perfectly preserved 

 down to their slightest details, are no longer composed of carbon- 

 ate of lime, as they certainly were during the life of the animal 

 to which they belonged, but are essentially different substances, 

 quartz having entirely taken the place of the calcium carbonate. 

 There are also other minerals, such as pyrites and sulphate of 

 baryta, which have penetrated and crystallized within the cavities 

 which the bodies of these invertebrates occupied. 



The silicified woods, which are very frequently met, assert still 

 more clearly the intervention of a liquid. Not only can the least 

 trained eye recognize their external shape, but the ligneous text- 

 ure also is still maintained, even to the cells and other inmost 

 parts, as distinctly as in the living wood. It is not, then, a simple 

 molding of silica, performed in the vacant spots that have been 

 left by the disappearance of the vegetable substance, but the ef- 



