Page:Quarterly Journal of the Geological Society of London, vol. 28.djvu/31

 locality*. It is situated about twelve miles from the river, and is about 100 feet higher than Pniel. The boulder-clays and gravels which are found nearer the course of the river appear to be wanting here. In many places the uppermost stratum is a red marl, largely impregnated with calcareous tufa ; in others, the tufa takes the place of the marl. Below this is a stiff red clay, called " Braakgrond " (fallow ground). Both these vary very much in thickness.

Beneath the clay is a deposit which has been described as a decomposed trappean (?) rock. This is full of angular fragments of many of the constituents of the other deposits, besides diamonds and innumerable small garnets. (See Nos. 13, 14, 15, in Appendix.) This stratum is twenty feet thick, and rests upon " clay-slate "(?). It has been described as out-poured volcanic rock, now decomposed ; and the pan itself has been termed a " crater" ; but this idea does not receive the least support from an examination of the deposit itself. Mr. Ella informs me that the floor of the pan is composed entirely of " clay-slate " [hard shale ?], and that in it no fissures can be traced through which an out-pouring could have taken place. The so-called " volcanic-ash " is merely a dark soil, strongly impregnated with calcareous tufa. The sharp, angular, fragmentary condition of most of the rocks found in the deposit above mentioned seems to indicate that the stratum in which they are now found could not have been their original matrix. Had it once been a molten mass, as has been suggested, these imbedded fragments would certainly have borne evidence of the intense heat to which they had been subjected. Again, in some portions of the diggings at the Pan these strata are said to bear unmistakable testimony of their being sedimentary rocks. My brother informs me that he has found leaf-impressions and plant- stems : unfortunately none of these have been preserved.

At a depth of seven feet from the surface, at one spot fragments of Ostrich egg-shells and some Bushmen-beads, made of the same substance, have been found, intermixed with a small univalve shell. To explain the position in which these were discovered, a suggestion has been ventured that, as the molten (?) mass contracted in cooling, cracks and fissures were formed, and a subsequent flow of water has washed these remains into the openings thus caused, and there buried them. Ancient relics of the same kind were found even at a greater depth at Jager's Fontein ; and I have seen similar traces of the primitive race of Bushmen obtained in other parts of the country, from beds of gravel fifteen feet below the surface ; I cannot, therefore, understand how the hypothesis above given can be supported†.

The characteristics of the Du-Toit's Pan deposits differing greatly from those nearer the river, no satisfactory explanation can be given until a careful analysis has been made of them.

Inferences. — In examining the foregoing sections of the gravels, it

Mag. February 1871, p. 52.— T. R. J.
 * See Mr. G. S. Higson's notes on its shales and dykes, quoted in the Geol.

† A small piece of Ostrich egg-shell, and several small flakes of agate, one of which has been used, probably in making beads, or perforated disks, of egg- shell, was found by me on examining a parcel of this gravel from Du Toit's Pan.— T. R. J.