Page:The American Cyclopædia (1879) Volume I.djvu/377

 ALPS 353 tions containing nummulitic limestone was interpreted by some to indicate that the car- boniferous flora survived longer in this region than elsewhere; while others explained the apparent anomaly by an inversion of strata. True granite is rare in the vicinity of Mont Blanc, but occurs in several localities, of which Val- orsine is best known. Both here and at the Col de Balme and the Aiguilles Rouges a por- phyroid granite sends veins into the adjacent gneiss, and appears to be true eruptive granite. Many of the apparently eruptive granites, how- ever, are claimed by M. Alphonse Faure, who has recently (1867) published a valuable work on Alpine geology, as the results of aqueous infiltration. The protogine of the Alps seems to differ from ordinary granite in composition, according to Delesse, in the presence of one or two hundredths of oxide of iron and magnesia. The crystalline protogine forms the centre of Mont Blanc and other peaks, and appears in a curious fan-like form extruded through the secondary strata by breaks which Elie de Beau- mont compares to gigantic buttonholes. The flanks are formed by crystalline schists. Both the protogine and the schists have been con- sidered by all who have studied them stratified rocks, gneissic in structure, passing in places into more schistose varieties, and by no means well separated from each other or the chloritic, talcose, or mica schists of the flanks. The un- crystalline strata in the neighborhood of Mont Blanc includes representatives of the carbonif- erous, triassic, Jurassic, neocomian, cretaceous, and tertiary. The anthracite system, as held by Scipion Gras, was estimated to have a thick- ness of 25,000 to 30,000 feet, and included, besides dolomites and gypsum, now referred by Faure to the triassic, layers of anthracite, coal plants, limestones containing belemnites of Ju- rassic age, gneissic, micaceous, and talcose rocks supposed to be due to the local alteration of members of the anthracite system. To this miscellaneous collection Fillet added in 1860 nummulitic beds. The many recognized dis- turbances of the strata were made to explain all anomalies of grouping to the satisfaction of some, but Sismonda and Elie de Beaumont, in a memoir presented to the academy of sciences at Paris describing the sections exposed by the Mont Cenis tunnel, hold that there is no evidence of inversion, dislocation, or repetition in the series of 7,000 metres of strata. Faure indicates the geological history of Mont Blanc, and of the principal portions of the Alps, as follows: In a shallow ocean covering gneiss and crystalline schists, the carboniferous beds were deposited ; some disturbance occurred, as secondary depos- its are laid down unconformably over all the old- er formations, gneissic as well as carboniferous ; then came the nummulitic limestones and their overlying sandstones, thus embracing a bed from the trias up of a thickness of about 3,800 feet; then came the great upheaval folding these strata, enclosing nummulites and coal plants in crystalline schists ; then the work of 24 VOL. i. 24: denudation removed the secondary strata, leav- ing a few evidences of their former existence, as in the beds more than 100 feet thick of Jurassic and infra- Jurassic age which cap the Aiguilles Rouges. The glacier action on the slopes of the Alps has been studied by De Saus- sure, Agassiz, Forbes, Tyndall, and others, and, from its extent and the comparative accessibil- ity of the Alpine glaciers, has furnished ground for almost all the present knowledge of the geological work of snow and ice on mountain slopes. The formation of the Alps can no longer be considered an event of recent geological periods, at least so far as the crystalline rocks are concerned, although perhaps the extension and exposure of these ancient crystalline rocks may be recent geologically considered. The phe- nomenon of transportation of vast blocks of rock across Alpine valleys will be treated of in the article DRIFT. Many metals are abundantly distributed through the Alpine strata, which will be more particularly described under the head of the different countries in which they occur. The great height of many of the Alpine sum- mits gives an extraordinary variety to their vegetation. At the base of the mountains it is very rich and beautiful, commingling the productions of a temperate clime with those of a more elevated region, the result of the seeds brought down by the mountain torrents. At the height of 1,600 or 1,700 feet we find a change ; the flora is less beautiful, though still rich and abundant; the primula auricula or bear's ear, the gentiana acaulis, the aconitum napellus or wolf's bane, the trollius Europeans, and the ranunculus aconitifolius, are the most characteristic plants. At 3,300 feet the sol- danella alpina, the crocus vernus, and two spe- cies of rhododendrons, adorn the declivities. At the height of 6,500 feet all the vegetation of the plains, including maize and the cereal grains, has disappeared ; the common fruit and forest trees have ceased, and dwarfish larch, alder, and birch trees have taken their places, soon to be succeeded by the stunted pine, pinus mugho, and cembra, above which, from the line of 7,450 to about 8,500 feet, ex- tends pasturage of a very rich and nourishing character, and a flora which from its peculiar character is distinguished by botanists as al- pine. Its principal genera are androsace, sile- ne, saxifraga, ranunculus, gentiana, and pyre- thrum. Of most of these, several species are found. Even amid the eternal snows, Agassiz distinguished several varieties of lichen. Ani- mal life is abundant throughout the Alpine chains. Herds of cattle find pasturage on their slopes; the wolf, fox, lynx, and wildcat abound in their forests; the bear hibernates in their caves ; the marmot and the mole bur- row in their pasture grounds. Several animals are peculiar to the regions ; among these are the chamois, which inhabits the upper limit of the forest region, the mountain goat, and a species of white hare. Among the birds of prey, the lammergeier, a gigantic vulture, is