Page:Popular Science Monthly Volume 33.djvu/658

640 which they can not have been deposited except by the intermediary action of water.

These views, which the direct observation of Nature had suggested to Elie de Beaumont, have been experimentally verified by De Senarmont. Working with close tubes under pressure, and at a temperature very much higher than that of boiling water, this eminent observer succeeded in reproducing the minerals of the veins from the most common substances—quartz, sulphate of baryta, fluor-spar, iron and copper pyrites, blende, sulphuret of antimony, glance, spathic iron, and carbonate of zinc; all of which laboratory-minerals, in a crystallized condition, quite resembled the analogous natural minerals. The fact of the contemporaneous formation of many of these, as exemplified in the basins of existing springs, as at Bourbonne-les-Bains, come later to confirm and complete this demonstration. Deep fractures or faults, which so numerously furrow the crust of the earth, have therefore endured various destinies in the series of the ages. Some have remained empty, or have been filled only with fragments detached from their walls. Others have furnished a way of exit for fluid eruptive rocks, basalts and porphyries, for example; and, finally, there are those with which we are now concerned, which have served, by the intervention of water, as channels for metalliferous emanations.

These emanations have not been borne exclusively into faults. Sometimes they have filled interstices of irregular and various forms, thus constituting ore-bearing masses, now adjoining eruptive rocks, as if they had followed them, now incased in stratified beds. Whatever their forms, these masses are often in relation with faults which have served as vents for emanations, partly watery, from the interior of the earth.

Among the metalliferous deposits of the last category, some, still better than the veins, demonstrate the intervention of mineral or thermal waters. The masses of hydrated peroxide of iron, frequent at Berry, where the Romans mined for them, and in Périgord, Lorraine, Franche-Comté, and other districts, have been attributed, with much probability, to the presence of gaseous springs, in which iron was dissolved as a bicarbonate. The form of globules with concentric laminations, or pitholiths, which they affect, strikingly resembles the little spheroids of carbonate of lime that are deposited every day in the basin from which the thermal springs of Carlsbad gush and whirl. At times we may recognize clearly that solutions of peroxide of iron have acted upon the limestone which they bathed, for they have gradually corroded it. This chemical action has also been exercised on animal and vegetable matters. At many places in Alsace the mineral contains minute fibrous fragments consisting of woody