Page:The Geologist, volume 5.djvu/66

48 a line of eight miles through Graham's Town and near Salem, at right- angles to this direction, it will pass through little but quartzite. If we draw a line of the same length through the Commadagga beyond the Zeurberg, it will pass through nothing but slates, Ecca rock, and clay stone porphyry.

3. On the road' to Graaff Reinet is a place called Wolve Krool. It is a plain, bounded by quartzite hills. Its section is this:—

Here the Ecca rock contains its characteristic fossils, is conformable with the quartzite, and is separated from the Dicynodon rocks by a highish mountain of quartzite and many miles of slate, porphyry, etc. I could add many other reasons for this belief, but I think these will be sufficient. What is then the true relation of the quartzite to the Ecca rock and the slates? and how is it that at one part of a line of strike the rock will be all of a blue slaty fossiliferous character, and at another all crystalline quartzite, destitute, or nearly so, of fossils? How is it that in deep sections, natural as well as artificial, such as are made by cutting roads or by deep gullies, the slaty rocks are found below gradually passing upwards into quartzite? Of this I could give scores of instances, but I will select only one natural one. The range of quartzite on the left-hand of the section is crossed by a bye-road. This road passes for a mile, or more over well-marked Ecca rock, with the high quartzite hills on either hand. The quartzite on the right-hand dies out, and the road to Graaff Reinet passes over Ecca rock in the corresponding part of the section.

I found what I believe to be the key to the explanation of these facts in Namaqualand. In passing through Ezel's Poort, between Springvontein and Spectakel, I was shown a section which had been noted by Dr. Atherstone as remarkable. The gneiss hills were covered by horizontal layers of quartzose sandstone, and these were continuous on the western side of the hill with like quartzose sandstone dipping at a high angle westward, conformably with the gneiss. It was clear that this change of dip was not due to any upheaval, for the horizontal sandstones were found undisturbed a few yards distant. I soon learnt to regard this juxtaposition of horizontal and inclined beds, this continuity of quartzite conformable and unconformable with its subjacent rock, as a normal state of things in Namaqualand. When I saw high mountains with like structure, I was at first a little staggered, but soon felt convinced that even on this scale the phenomenon was due to the assimilation to each other by a process, common to both, of rocks of widely different ages.

In the Western Province I made, in a rapid journey from Cape Town to Ceres, a selection from the clay-slate to the Upper Silurian of Bain. I had reason, as far as I was able, to confirm the truth of Mr. Bain's section, while differing from him in the inference I drew