PHYSICAL GEOGRAPHY OF THE CAPE COLONY. 253 



we know as yet on the subject is directly in the teeth of such a 

 result. We do know that the coals vary enormously in thickness 

 and value from place to place ; for instance there is good reason to 

 think that the worthless coal of Van Zyl's Farm belongs to the 

 very same bed which yields at Molten o, only about a mile oif, a 

 marketable coal. There is some reason to think that the coals were 

 originally deposited in detached patches. It is certain that in some 

 cases they were largely mutilated by contemporaneous erosion very 

 shortly after their deposition. In view of these facts, such an 

 assumption as is involved in the estimates in question is wholly 

 unjustifiable, and any attempt to appraise the value of the coal- 

 deposits of South Africa must be altogether premature. 



(9 b, 9 c, 9 d.) Of these subdivisions I have scarcely anything to 

 say, for I saw them only at one spot, on the slopes of Yaal Kop, the 

 highest point of the Stormbergen, about 12 miles to the east of 

 Molteno. 



Here, above beds of decided Molteno type, we find a group of 

 shales, with sandstones neither thick nor coarse, of a deep red 

 colour, and above them more massive reddish sandstones. These 

 are the " Red Beds " of Mr. Dunn. He puts them down as 600 

 feet thick and says that reptilian remains occur in them. Next 

 follows a finely grained, light-coloured sandstone, which weathers 

 white, about 150 feet thick, Mr. Dunn's " Cave Sandstone." It is 

 extremely massive, no planes of bedding being visible through its 

 whole thickness ; and it forms magnificent precipitous escarpments 

 along the hill-sides. Miles away these lines of white cliffs stand 

 out in the clear atmosphere sharp and distinct ; or an outlier, capping 

 an isolated hill-top, makes a landmark, visible over all the country 

 side. I saw from a distance just the same white cliffy scarps 

 running along the slopes of the Draakensberg ; and again when I 

 was at Winburg in the Orange Pree State my eye was caught by 

 mountains well away to the south with the same white capping. 

 In the Club at Burgersdorp there were some very clever sketches of 

 the Basuto Mountains, not drawn by a geologist, but there was no 

 mistaking the Cave Sandstone in them. 'No rock that I ever saw 

 makes such characteristic features. On the farm Wonder Hoek, 

 at the foot of Yaal Kop, the Cave Sandstone gives rise to wild and 

 striking scenery. There is a ramification of valleys and the escarp- 

 ment winds in and out of each of them in rugged undercut preci- 

 pices of from 100 to 150 feet high, the slopes above and below 

 being comparatively gentle. The precipitous escarpments are very 

 largely undermined by the weather, and thus enormous rock- 

 shelters or " caves " are formed, whence the name of the rock. 

 Above the Cave Sandstone comes a group of bedded amygdaloidal 

 lava-flows and tufts, the " Volcanic Beds " of Mr. Dunn. A pecu- 

 liarity in these are the so-called " Pipe Amygdaloids," in which the 

 rock is traversed by a number of vertical, winding, tubular cavities, 

 filled in with a zeolite. These are described by Dr. Cohen, ' Neues 

 Jahrbuch fiir Mineralogie,' 1875, p. 113, 1880, vol. i. p. 96. My 

 specimens of these lavas are described on p. 255. 



