Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/688

 indications must surely prove that here they must have been deposited in still water, below or beyond the influence of the tidal and other waves ; while, on the other hand, the shells of the "raised beach" appear to have been deposited on a kind of outer reef, exposed to the full force and constant action of the sea, which broke them into fragments, and rounded off their fractured edges.

§ 4. The Red Clay. — The deposit which seems to follow these is the red clay, as shown at g g, in Section (fig. 4). The exact position of this clay, to which I have before alluded (p. 518), requires more careful examination than has yet been given to it. There appears to be little doubt, from the section just referred to, that it must be more recent than the shell-deposits we have been describing ; for upon the flat, at a little distance from the north end of Port Elizabeth, they are found cropping up through it. These shell-beds, judging from their fossils, are identical with those of Ferreira's River. However, as I have said, little is at present known of this clay, except that it varies considerably in thickness in different localities: thus it may form merely a superficial covering to the shell- banks mentioned; while the late Dr. Rubidge informed me that at the New Prison it is some 60 or 80 feet thick ; and, at Oliphants Hoek, Dr. Atherstone states it to be 100 feet. Whatever may be its thickness, it must have been deposited under totally different circumstances from any thing preceding it. The transition from the one to the other is so sudden that, with the limited information we have about it, it will have to be left to future investigation before its history can be written, as well as to discover (what is probably the case) deposits on other parts of the coast that may intervene between the shell-banks and the clay, and others between the clay and the formation which follows, thus more clearly explaining the changes that led to its deposition.

§ 5. Latest Shell-heels. — The next known deposit of the ancient sea is that marked C, C, in section T No. 1, and C in T No. 2. This is evidently the most recent, previous to the existing order of things. In the Bight, as shown in the section, it is found in detached mounds of drift-sand, with a thick horizontal bed of shells on the top. These, however, from their position and structure, are merely the isolated remains of what, at one time, was a continuous and wide-spread deposit. It is found on different parts of the coast, and is especially remarkable on the south side of Port Elizabeth, towards a small indentation called the Shark's-River Mouth. In this locality the quartzite rocks (near the top of the ridge, and at an elevation of 180 feet above the sea) have been worn away to a long slope by the action of the waves &c. About one-third up the ascent, and resting upon the quartzite, is a mass of conglomerate composed almost entirely of quartzite fragments imbedded in limestone, with fragments of shells. There is another accumulation of conglomerate at the same place, at a lower level, composed of waterworn pebbles. These conglomerates have been found at other parts of the coast. Upon this conglomerate, or, where it is wanting, upon the quartzite itself, are