Imatges de pÓgina

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 declivity. 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 embedded 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 approaches 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 miles, 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

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

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.

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 nodules of quartz.

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 granular 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 afterwards 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 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 superior in quality to that in the im

mediate 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 speaking, composed of coral, as was evident by our lead never descending to the bottom without bringing up coral on its return, but by coral being found on the highest hills we ascended, particularly on the summit of Bald Head, which is sufficiently above the level of the sea to be seen 12 or 14 leagues distant. Here the coral was entirely in its original state, particularly in one level spot, comprehending about eight acres, which produced not the least herbage on the white sand that occupied this space, through which the branches of coral protruded, and were found standing exactly like those seen in the beds of coral beneath the surface of the sea, with ramifications of different sizes, some not half an inch, others four or five inches in circumference. In these fields of

coral, (if the term field be allowable,) of which there were several, seashells were in great abundance, some nearly in a perfect state, still adhering to the coral, others in different stages of decay. The coral was friable in various degrees; the extremities of the branches, some of which were nearly four feet above the sand, were easily reduced to powder, whilst those close to, or under the surface, required some small force to break them from the rocky foundation from whence they appeared to spring. I have seen coral in many places at a considerable distance from the sea; but in no other instance have I seen it so elevated and

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