Giesti Gubib, an Old Volcano. 
249 
valley a baranco, and compares the mountain with Rochlitz Berg in 
Saxony, but notes that the latter does not retain its original shape ; other- 
wise this description is much the same as the one quoted above. 
In another article (" Das Deutsche Kolonialreich," 1910, vol. ii.) he 
mentions it as an old volcanic cone made of porphyry-tuff. 
Eeferences to Eochlitz show that there are beds and piles of hardened 
tuffs of Permian age there, and that the tuffs are made of lapilli of por- 
phyry and crystal fragments set in a compact ground-mass. These 
features are not quite like those of the Geitsi Gubib rocks, as will be 
seen later. 
Geitsi Gubib is a ring-shaped mountain rising about 5,200 feet above 
sea-level and 1,800 feet above the high plateau on which the village of 
Berseba stands. The mountain lies nine miles north of the village, and is 
a very conspicuous object from the railway north of Keetmanshoop. The 
plateau here is made of red sandstone and marls or shales belonging to 
the Fish Eiver series, which is well exposed in the steep sides of the valley 
of the Fish Eiver in this neighbourhood. The lowest beds of the Karroo 
system, Dwyka tillite and the overlying shales, are seen on the left side of 
the river near Dairacharab Drift, and tillite alone on the right side, resting 
on the nearly horizontal Fish Eiver beds, but the Karroo rocks do not 
reach Berseba or Geitsi Gubib, where they have been removed by 
denudation. 
The mountain itself is made of masses of fine-grained clastic rocks and 
breccias forming thick beds with steep dip towards the centre of the 
mountain (see Fig. 1 and section). The dip is often as high as 30°, and 
individual beds may be as much as 50 feet thick. Only the south-western, 
southern, eastern, and north-eastern sides were visited, but it seems that 
any one variety of rock has a limited distribution and is replaced within a 
few hundred yards by a slightly different variety, the difference being in 
colour, grain, and frequence of small angular fragments. A deep valley 
draining the central depression leads south-east to the surrounding 
plateau. The central depression, 1,500 feet below the highest point on 
the ridge, is flat and is covered with debris washed down from the 
steep wall round about it. A well had been sunk in approximately the 
middle of the depression, but it was partly filled in at the time of my 
visit. The material dug out of the well appears to have been soft and 
gritty, in fact the same kind of stuff as the tine-grained hard rocks of the 
wall but without the cement. 
The contact of these fragmental rocks with the Fish Eiver beds is well 
exposed in the walls of the valley cutting through the southern part of the 
ring. It is vertical or nearly so, and though this is the only place where 
* j. Walther, " Geologie von Deutschland," 1910, p. 248; Eosenbusch, " Ergussges- 
teine," p. 871 ; and Zirkel's " Petrogvaphie," vol. iii., p. 660, 
