GEOLOGY. 
27 
strata of red or white sandstone, thus adding to the remarkable contrast of the scene. In 
front of us, and to the right, stretched in a semicircle a regular old Somma; the almost 
perpendicular walls rising to about 1,500 feet above the river, and clearly exposing the stratifi¬ 
cation of the basaltic flows, which were successively dipping to north-east, east, and south¬ 
east. On our left, as well as in an almost due western direction, portions of a similar Somma 
were visible above the sedimentary rocks, all dipping in the opposite way from those ahead 
of us. The cone itself has in reality entirely disappeared by subsidence, and the cavity was 
filled with the rubbish of the neighbouring rocks. 
Passing further north we crossed a comparatively low country, studded with small rounded 
hills and intercepted by short ridges, with easy slopes; the average height was between 12,000 
and 13,000 feet. This undulating high plateau proved to be one of the head-quarters of the 
Kulja (Ovis karelini), chiefly on account of the very rich grass vegetation which exists here. 
Eor this the character of the soil fully accounts. The entire ground was shown to consist of 
limestone gravel and pebbles of rather easily decomposing rocks, mixed with the ashes and detri¬ 
tus, evidently derived from the proximity of the volcanic eruption. Only rarely was an isolated 
basaltic dyke seen, or the tertiary sandstone cropping out from under the more recent deposits. 
Viewing the country from an elevated position near our camp at Turgat-bela, the 
conglomerate and gravel beds, well clad with grass vegetation, were seen to stretch far away 
eastwards, and in a north-easterly direction across the Turgat pass; while on the south they 
were bounded by a continuation of the somewhat higher basaltic hills. Towards the west 
I traced them for about 7 miles, across a low pass at which a tributary of the Toyanda 
rises in two branches; while on the other side two similar streams flow west by south to join 
the Suyok river. To the north the proximity of a rather precipitously rising range shut the 
rest of the world out of view. Eor this ridge the name Terak-tagh of Humboldt’s map may 
be retained; its average height ranges between about 16,000 and 17,000 feet. In its 
western extension it runs almost due east and west, composed at base of a tough limestone 
conglomerate of younger tertiary origin, followed by white dolomitic limestones, and then by 
a succession of slaty and dark limestone rocks, the former occasionally showing distinct 
signs of metamorphism, and changing into schist. All the beds are nearly vertical or very 
highly inclined, dipping to north by west, the older apparently resting oil the younger. 
ISTorth of Turgat-bela the range makes a sudden bend in an almost northerly direction, 
and continues to the Chadyr-kul, where it forms the southern boundary of the lake plateau. 
By this time the white dolomitic, and afterwards the slaty beds, have entirely disappeared, 
and with them the height has also diminished. A comparatively low and narrow branch of 
the range which we visited consists here entirely of dark limestone, which in single frag¬ 
ments is not distinguishable from the trias lim estone of the Koktan mountains, but here 
it does not contain any fossils. The ridge itself, after a short stretch in a north-east by north 
direction, gradually disappears under the much newer conglomeratic beds. 
Across the Chadyr-kul plain the true Thian Shan range was visible, a regular forest of 
peaks seemingly of moderate and tolerably uniform elevation. The rocks all exhibited dark 
tints, but most of them, as well as the hills to the west of the Chadyr-kul, near the sources 
of the Arpa, were clad in snow. The lake itself was frozen, and the surrounding plain covered 
with a white sheet of saline efflorescence. 
Brief sketch of the geological history of the hill ranges traversed. — In order that the 
preceding remarks. may be more easily understood, I add a few words regarding the changes 
