368 



THE GEOLOGIST. 



that I think six or seven geographical miles for the depth of the sec- 

 tion is a low estimate. A glance at the sketch would show that a few 

 miles on in the strike a parallel line would pass through nothing 

 but quartzite. 



The quartzite mountains, therefore, and their spurs, cross the slate 

 at considerable angles to the strike of the latter, and the mountain 

 ranges enclose large angular areas of slate. I have stated just now 

 that two parallel lines could be drawn, at the distance of some miles 

 apart, which should cut a corresponding portion of the strike of the 

 slate. Taking the smaller spurs of the ranges, and giving the lines no 

 very considerable curve, two such lines might be drawn within two 

 miles of each other. My reason for dwelling on this relation will ap- 

 pear presently. I would now beg of any geologist who has followed 

 me thus far to pause and reflect on these relations of the slate and 

 quartzite, and before proceeding to answer to himself, and if not too 

 great a favour, to me, through the ' Geologist,' the following ques- 

 tions : — 



1st, Supposing the relations just described to be correctly repre- 

 sented,* is it not clear that Mr. Bain and the other authorities quoted 

 are right in classing the slates with the old rocks, and making the 

 quartzite a newer and independent formation ? 



2nd, If the geologist should find rocks resting conformably on the 

 same quartzite, would he not refer them (same postulate) to a much 

 newer formation than the slate ? 



This is simply what Mr. Bain has done. 



I will suppose it admitted that the clay-slate of the region between 

 the Kromme and the Kabeljouw and Gamtoos rivers is probably of 

 identical and continuous formation with that of Cape Town, and that 

 of the quartzose rocks which cross it at various angles to its strike, 

 are continuous and identical in character with those of Table Moun- 

 tain. Then I think it will not be disputed that these slates must 

 have been upheaved into their present positions long ere the deposi- 

 sition of the quartzose sandstone or its assumption of its present con- 

 dition, which Darwin attributes to the infiltration of silica. 



Let us now see what grounds we have for forming a judgment as 

 to the age of these slates, reminding the reader that Mr. Bain, from 

 sections which I believe to be mainly correct, referred them to an 

 epoch long preceding the Lower Silurian, which strata, resting on 

 the quartzite, are supposed Upper Silurian (Devonian of European 

 geologists), and rocks interstratified with like quartzite at the Mait- 

 land Mines and the eastern province generally are called Carbonife- 

 rous. 



Some time after the relations of the quartzite with the palaeozoic 

 and mctamorphic rocks, observed in Namaqualand and in this pro- 

 vince, had led me to predict that the former, throughout the colony, 

 would be found to belong to one formation, Mr. Niven, of Jeffreys 

 Bay, undertook, at my request, to search for fossil evidence bearing 



* I have borrowed the pencil of a friend, Mr, R. Miller, to represent these relations 

 more clearly to the eye. It is doubtful if the relation of the strike will be understood. 



