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 metamorphic rocks, observed in ^s'amaqualand 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 JeflTreys 
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 vvill be understood. 
