464 Notices of Memoirs—Ancient Volcanoes of Basutoland: 
amounts to 6,000 feet, of which the volcanic beds amount to 4,000 
feet. The sandstones 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 Malote. 
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, etc.; the second 
of Dikolobeng, Mokhele, etc.; 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 voleanic beds consist of lavas and ashes, with occasional 
silicious tuffs, intersected with intrusive sheets and dykes. - Most 
of the lavas are amygdaloid ; scoriaceous varieties also oceur, 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. JBasaltic 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, surrounding what was formerly 
a subsidiary cone, but is now nothing more than a mere conical plug 
of agglomerate. q 
(2) Thaba Tsuen. This mountain is slightly lower than the pre- 
ceding, 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 voleanic 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. 
(3) 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 composition of the lava beds is similar to Thaba de 
