518 TRANSACTIONS OF SECTION C. 
sub-continent. Upon this plateau, as a foundation, stand the great volcanic 
ranges, more than 11,000 feet high. 
From the Caledon River to the edge of the great volcanic plateau is about 
fifteen miles. This plain is fairly level, and is interspersed with flat-topped 
mountains rising to 1,500 feet above the plain. These represent the original level 
of the country. The geology of the country is exceedingly simple. It is filled with 
the Stormberg series, lying nearly horizontal. The total thickness of these rocks 
amounts to 6,000 feet, of which the voleanic beds amount to 4,000 feet. The sand- 
stones are loose and friable, and contain remains of plants, dinosaurs, and crocodiles, 
The volcanic beds are the most striking rock features of the country, as they 
compose all the highest summits of the great ranges of mountains known as the 
Drakensberg and Malite. 
The vents from which the lavas and ash proceeded which have built up these 
great piles of rock can be roughly arranged in three or four parallel lines, 
corresponding to the present ranges of mountains. The first range consists of 
Machache, Thaba ’Telle, &c.; the second of Dikolobeng, Mokhele, &c.; the third 
of Mount Hamilton and Motai; and the last of the great summits of the 
Drakensberg, such as Mont aux Sources, Champagne Castle. Most of these 
mountains are 10,000 feet high and upwards. The rivers run in the synclines 
between these ranges of mountains, as a glance at the map shows. 
The volcanic beds consist of lavas and ashes, with occasional silicious tufts, 
intersected with intrusive sheets and dykes. Most of the lavas are amygdaloid ; 
ecoriaceous varieties also occur, but they are much less common, The beds are 
often full of pipe-like vesicles, filled with calcite, but often empty. These 
vesicles are inclined towards the vent. Basaltic lavas are common, and andesites 
also occur. 
A short description of four of the most prominent peaks will serve as examples 
of the others, 
(1) Thaba ’Telle. It is about 7,800 feet high, with steep—in some places 
precipitous—sides. It is composed of doleritic amygdaloid lavas, alternating with 
beds of ash. The plug is agglomerate, evidently the remains of the old throat. 
The lavas are full of steam holes. Thick deposits of purple ash also occur. Near 
the base of the mountain is a large intrusive sheet, surroinding what was 
formerly a subsidiary cone, but is now nothing more than a mere conical plug of 
agglomerate. ; 
(2) Thaba Tsuen. This mountain is slightly lower than the preceding, but of 
beautiful conical shape. The height is 7,529 feet. It consists of two terraces 
and the agglomerate plug. The total thickness of lavas, ashes, and agglomerate 
is 1,600 feet. The plug proper rises from the second terrace, which slopes gently 
inwards, indicating the roots of the old cone. The plug is composed of coarse 
doleritic lava and agglomerate, and is about 500 feet high. It is a prominent 
landmark, and even more typically volcanic than many of the other peaks. The 
deposition of the lavas was not continuous, as there are thin intercalated beds of 
sandstone. The same feature occurs on all the other mountains examined. 
(8) Thaba de Noha. This is a portion of the great Mokhele range. The 
plug and a portion of the old crater-walls remain. The lavas at one point are 
glassy, and steeply inclined, at another scoriaceous. There are also thick beds of 
ash, The characteristics of the lavas in this range are similar to the peaks 
previously mentioned, 
(4) Thaba ’Ntso. This mountain is 7,560 feet high. It is part of a great 
range running perpendicular to the course of the Orange River. The com- 
position of the lava beds is similar to Thaba de Noha, the principal difference 
being that the beds of ash are thicker and better consolidated, evidently pointing 
to deposition in deeper water. 
Many of the very highest peaks, such as Mont aux Sources, Motai, Mount 
Hamilton, are not described here, as the writer has never been able to visit 
them. 
A short notice of the intrusive sheets and dykes is a necessary complement tc 
