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Granite forms a considerable portion of the Lion's Head. It is composed of pale-red felspar, gray quartz, and brownish-black mica. It is more frequently coarse granular than fine granular, and is often porphyritic. It is occasionally traversed by veins of quartz, or of felspar, or of granite. In some parts the granite is traversed by veins of dolerite or augite-greenstone, and one of these veins, as described by Dr. Abel, appears divided and shifted. This appearance is.. represented in No. 3 of Dr. Abel's Geological Views at the Cape of Good Hope. As we ascend the mountain, we find the granite succeeded first by a reddish sandstone, and this, in its turn, is covered by a brown sandstone that reaches to the summit. These sandstones are principally composed of granular concretions of quartz, with a few disseminated grains of felspar and scales of mica. The sandstone is distinctly stratified, and the strata dip at a small angle all around the Lion's Head and the north-west side of the Table Mountain. On the opposite side of the latter, however, from the seabeach, we may see it, beyond the gorges, making an angle with the horizon of not less than 45°. Dr. Adams says, "During a ride to Constantia one day, I observed this high inclination more particularly on the ridge extending from the Devil's Peak by Simon's Bay; and, having afterward visited the spot on purpose, found the sandstone very much elevated in its position above the common level of the strata, and, at one place, nearly perpendicular to the horizon, running from north-east to south-west."
Table Mountain. The next and highest mountain, the Table Mountain, presents many interesting appearances. The lowest part of the mountain, on one side, is red sandstone; higher up, and apparently rising from under it, are clay-slate, greywacke, and gneiss. These rocks are disposed in strata, arranged nearly in a vertical position, with an east and west direction. They are intermingled with granite, which is the next rock on the ascent of the mountain. The granite, at its line of junction with the slate, both gneiss and clay-slate, is often much intermixed with them; and numerous veins of granite shoot from the mass of the granite rock itself into the bounding strata. At a higher level than the granite, sandstone makes its appearance, and continues upwards to the summit of the mountain. The lowest of the summit sandstone is of a reddish
colour; the next above it is of a yellowish colour; and the upper part, or that on the summit, is of a gray or beautifully white colour, and sometimes so coarsely granular as to appear in the state of conglomerate. In many places, the sandstone passes into quartz rock, and is very highly crystalline. The sandstone is distinctly stratified, and nearly horizontal.
Devil's Peak.-The most easterly mountain of the group we are describing, named the Devil's Peak, agrees with Table Mountain in the nature and arrangement of the rocks of which it is composed. The lower part of the mountain exhibits strata of clay-slate; these, as we ascend, are succeeded by granite; and the upper parts and summit are of the usual varieties of sandstone.*
*The following particulars, in regard to the mountains near Cape Town, were communicated to us by Captain Carmichael. The Table Mountain and Lion's Head rest upon a base of granite; Green Point, Table Valley, and the Devil's Peak, on a base of slate, of which the whole of the Lion's Back or Rump is composed. The granite extends up to the rocky crown of the Lion's Head, an elevation of nearly 1500 feet; and the declivity of the mountain is strewed with enormous masses of it. On the side of the Table Mountain, the space on which the granite is visible is contracted to about 500 feet, and occupies the centre of the decli vity. At the spot called Sea Point, the granite and slate come in contact. In the space of 200 yards along the shore, the reef is a mixture of these two rocks, each predominating in the mass as you approach its respective side, where it is pure and unmixed. In some parts they form alternating layers; in others, fragments of the slate, of all figures and sizes, lie imbedded in the granite, which appears to have pervaded their minutest fissures. Between this mixed mass, however, and this pure slate, there is interposed a rampart of granite, apparently different from the common sort, which, for about 200 yards, is unmixed; but, as it ap proaches the slate, becomes mingled with it in the same manner as the granite. From this to Green Point, and extending through Robben Island, a distance of about twelve railes, the slate is pure, and disposed in nearly vertical strata.
Close to the path which leads from Cape Town to the summit of the Table Mountain, there runs a stream, which, at the point where the granite and slate meet, has carried off the superincumbent earth, and exposed the surface of the rock from ten to twenty yards in diameter, and about 200 yards in length, dipping at an angle of about 30°. Along the whole of this space the slate is intersected by veins of granite, varying from three feet in width to as many lines. The veins branch off in all directions, some straight, others twisted in the most fantastic convolutions. In the face of the rampart which borders the channel on each side, the veins are equally conspicuous. In walking along the shore, from Campo Bay to Sea Point, we meet with numerous veins of augite greenstone in the granite, varying in breadth from an inch to ten feet, and branching in as many directions as those of the granite with the slate. Here also are to be seen numerous fragments of slate in the granite.
To what Class of Rocks do those of the Cape Peninsula belong?-To what class or classes of formations of the geognostical series are we to refer the rocks of the mountains just described? From the clay-slate containing beds of greywacke, we infer that the slate belongs to the transition class;-from the granite being intermingled with the slate, we consider it as probably belonging to the same epoch. The sandstone is generally considered as belonging to the secondary class,-an opinion, the accuracy of which may be questioned; because we find this rock in beds in the slate, and also passing into and alternating with beds of a transition rock, namely, quartz rock. This being the case, we are disposed to refer it also to the transition class; and the great mass of it to the newest or uppermost portion of the series.
At what Period did the Cape Rocks rise above the Level of the Sea? This question has been variously answered, according to the geological creed of those who have considered the subject. The Neptunians maintain, on plausible grounds, that all these rocks are crystallizations and deposites from the ancient waters of the globe, which have taken place in succession, the granite being the first formed, the slate and greywacke the next, and last of all, the principal portion of the sandstone; that, during the deposition of these different rocks, the level of the ocean gradually sunk; and that thus the mountains rose above its surface. The Plutonians, or the supporters of the igneous origin of the gra nular crystallized rocks, view the formation in a different manner. Some of the advocates of the igneous system maintain, that the slate was first deposited in horizontal strata, at the bottom of the sea,-that these strata were afterward softened by heat, and raised from their original horizontal to their present highly inclined position, by the action of fluid granite rising from the interior of the earth; and that in this way the granite and slate mountains were elevated above the sea: that the sea again invaded the land and covered it to a great depth; and that from this ocean was deposited the sandstone strata: that the sea again
The sandstone which forms the upper part of the Table Mountain, Lion's Head, and Devil's Peak lies on horizontal strata, intersected by vertical fissures. It is of a siliceous nature, and encloses rounded no dules of quartz.
retired, and left exposed mountains, and chains of mountains of sandstone. Other Plutonians are of opinion that the slate, greywacke, and sandstone were deposited, in uninterrupted succession, at the bottom of the sea; and that the whole mass of stratified matter was raised gradually or suddenly above the level of the ocean, forming mountains, chains of mountains, and table-lands, by that igneous agency which sent up the granite, and probably also the augite-greenstone rocks. This, of the two Plutonian views, is the most plausible, and indeed is that explanation which may be viewed as most in accordance with prevailing geological hypotheses.
Vegetables incrusted with Calcareous Sand confounded with Coral, and adduced as a Proof of the very recent Emergence, from the Ocean, of the Lands supporting them.-Somewhat to the eastward of Simon's Town is a large bank, one hundred feet above the level of the sea, formed by an accumulation of sand and shells, brought there by the action of the wind. On this bank Abel observed a number of cylindrical calcareous bodies scattered about, which at first appeared like bleached bones. On a closer examination many of them are found to be branched, and others are discovered rising through the soil, and ramifying from a stem beneath, thicker than themselves. They are incrustations of sand and calcareous matter on vegetables. Similar bodies have been found by Vancouver, Flinders, and Perron, on the shores of New-Holland, at considerable elevations. The first-mentioned traveller considered them all as coral, and as proofs of the land having been lately withdrawn from the dominion of the waters. The last has described two kinds of substances; the one he considers as coral, the other as incrustations on vegetables. Captain Flinders, at page 48, vol. i. of his Voyage Round the World, says,-" The appearance of this country along the coast resembles, in most respects, that of Africa about the Cape of Good Hope. The surface seemed to be chiefly composed of sand, mixed with decayed vegetables, varying exceedingly in point of richness, and, although bearing a great similarity, yet indicating a soil su perior in quality to that in the immediate neighbourhood of Cape Town. The principal component part of this country appeared to be coral; and it would seem that its elevation above the ocean is of modern date, not only from the shores and the bank which extends along the coast being, generally
RECENT EMERGENCE OF LAND DISPROVED. 281
speaking, composed of coral, as was evident by our lead