The texture and quality of these columns are not less different than their forms. Those of the Monte del Diavolo present a smooth surface, and, when broken, appear within of a dark iron-gray color, manifesting also a very solid and uniform texture; in which characters they correspond with the columns of the Giant’s Causeway, and those of most other basaltic groups. But the columns of Monte Rosso are in these respects very different, having not only a very rough (and sometimes knotty) surface, but displaying likewise, when broken, a variegated color and unequal texture of parts. They are commonly speckled, more or less distinctly, and resemble an inferior sort of granite, of which Monte Rosso is itself formed, and which serves as a base to the range of columns in question. It is, in general, not quite so hard as the alpine and oriental granites, and is sometimes even friable. This species of granite abounds in France, where large tracts of it are to be seen in Auvergne, and the adjoining regions. But it is still more common in Italy, seeing that, besides Monte Rosso, the bulk of the Euganean hills, of which that is a part, principally consists of it; and these hills occupy a considerable tract in the plains of Lombardy. It is also common in the Roman and Tuscan states; and of this substance the mountain close to Viterbo, on the road to Rome, is entirely composed. The columns of Monte Rosso appear, therefore, of a different character from any hitherto described by mineralogists, who mention those only of an uniform color and texture. But the great singularity here is, that such a range of prismatic columns should be found, bedded as it were, in a mass of granite, and composed nearly of the same substance. An instance of this kind, relative to any other causeway, is not recorded; and this circumstance seems to render that of Monte Rosso, in one respect at least, more curious and singular than the celebrated Giant’s Causeway is known to be, from the regular articulation of its columns. It is certain, that the basaltic group of Monte Rosso is not only highly curious in itself, but interesting on account of the great light it throws on the origin of granites in general.
It is likewise remarkable, that the columns in the two groups of Monte Rosso and Monte del Diavolo, preserve respectively the same position, nearly parallel to each other; which is not usually the case in basaltic groups. For, although the principal aggregate of which the Giant’s Causeway is formed, stands in a direction perpendicular to the horizon, still other small detached groups of columns also appear on the eminence above, assuming by their position different degrees of obliquity. Among the numerous basaltic hills of Auvergne and the adjoining regions, in France, phenomena which seem to abound in those provinces more than in any other part of Europe, and, perhaps, of the known globe, nothing is more common than to see the columns of the same group lying in all possible directions, as irregularly almost as the prisms in a mass of common crystal. Nor is this variety of position so observable in single columns as in whole masses or ranges of them, that often present themselves on the same hill, disposed in different strata or stages, as it were, one above the other, many of them assuming very different, and even opposite directions. The columns of the Monte del Diavolo are bedded in a kind of volcanic sand, by which, in many parts of the hill, they are entirely covered: it is probable, however, that they repose beneath on a base of basaltic rock of a similar nature. Nothing is more common, in the provinces of France, above mentioned, than to see insulated basaltic hills almost exclusively composed of different layers of columns, which present themselves in stages, one above the other, often without any other stratum between them, resembling in some measure, if the comparison can be allowed, a huge pile or stack of cleft wood. Although the columnar crystallization of Monte Rosso is the only one yet known or described, in a mass of granite, still other groups of columns have elsewhere been met with, which are equally of a heterogeneous substance or texture, however they may otherwise differ from those of Monte Rosso, as well as from the common basalts.
NATURAL BRIDGES.
NATURAL BRIDGES OF ICONONZO.
Amid the majestic and varied scenery of the Cordilleras of South America, that of their valleys most forcibly strikes the imagination of foreign travelers. The enormous hight of these mountains is not discoverable but at a considerable distance, and while the spectator is on one of those plains which extend from the sea-coasts to the foot of the central chain. The flats, or table-lands, which surround the snow-clad summits of the mountains, are themselves, for the greater part, of an elevation of from seven to nine thousand feet, or nearly a mile and three-quarters, above the level of the sea. This circumstance diminishes, to a certain degree, the impression of greatness produced by the colossal masses of Chimborazo, Cotopaxi, Pichincha, &c., when seen from the flats of Riobamba, or from those of Quito. It is not, however, with the valleys as with the mountains: deeper and narrower than those of the Alps and the Pyrenees, the valleys of the Cordilleras present situations still more wild than these, and more adapted to fill the soul with admiration and with terror. Fissures and chasms present themselves, having their bottoms and sides ornamented with a vigorous vegetation, and of such a depth, that Vesuvius and the Puy-de-Dome might be placed within several of them, and not show their summits above the edge of the neighboring mountains. In passing along the back of the Andes, from Pasto to Villa d’Ibarra, and in descending the Loxa toward the banks of the river Amazon, the traveler reaches the celebrated fissures of Chota and Cutaco, the former of which is nearly a mile, and the latter upward of three-quarters of a mile, in perpendicular depth. To give a more complete idea of the grandeur of these geological phenomena, it should be observed, that the bottoms of these fissures are by one-fourth only, less elevated above the level of the sea, than the passages of St. Gothard and Mount Cenis.
The valley of Icononzo, or of Pandi, is less remarkable for its dimensions, than for the extraordinary form of its rocks, which appear as if shaped by the hand of man. Their naked and barren summits form the most picturesque contrasts with the tufts of trees and herbaceous vegetables which cover the edges of the fissure. The little torrent which has worked itself a passage through the valley of Icononzo, bears the name of Rio de la Summa Paz. It descends from the eastern chain of the Andes, which, with the republic of New Grenada, separates the basin of the river of Magdelena from the vast plains of the Meta, Guaviare and Oronoco. This torrent, confined within a bed almost inaccessible, could not have been crossed without many difficulties, had not Nature herself formed TWO BRIDGES OF ROCKS, which are justly regarded in the country as among the objects most worthy of the attention of travelers. These NATURAL BRIDGES are on the route from Bogota to Popayan and Quito.
Icononzo is the name of an ancient village of Muyscas Indians, situated on the south side of the valley, and of which scarcely any vestige now remains, except a few scattered huts. The nearest inhabited place to this remarkable spot is the little village of Pandi, or Mercadillo, distant about a mile. The road from Bogota to Fusagasuga, and thence to Pandi, is one of the most difficult and least beaten to be met with in the Andes. None but those who passionately love the beauties of Nature, would fail to prefer the usual road which leads from the flat of Bogota to the banks of the Magdelena, to the perilous descent from the Paramo de San-Fortunato, and the mountains of Fusagasuga, toward the natural bridges of Icononzo.
The deep chasm through which the torrent of Summa Paz precipitates itself, occupies the center of the valley of Icononzo. Near the first natural bridge, it maintains, for a length of nearly four-fifths of a mile, a direction from east to west. The river forms two fine cascades, the one at the spot where it enters the chasm on the west of Doa, and the other at that where it leaves it, in descending toward Melgar. It is possible that this chasm, which resembles, but on an enormous scale, the gallery of a mine, may have been the result of an earthquake, and that, at its formation, the compact bed of quartz, composing the superior stratum of rock, had resisted the force which tore asunder these mountains. The uninterrupted continuation of this quartzose bed would thus form the bridge, which affords a passage from one part of the valley to the other. This surprising natural arch is forty-eight feet in length, forty in width, and eight feet in thickness at the center. By experiments carefully made on the fall of bodies, its hight above the level of the water of the torrent, has been ascertained to be about three hundred and twenty feet. The depth of the torrent at the mean hight of the water, may be estimated at twenty feet. The Indians of the valley of Icononzo, for the security of travelers, have formed a fence of reeds, which extends to the road leading to this first natural bridge.