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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 Polii), chiefly on account of the very rich grass vegetation which exists here.
For 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
detritus, 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 Turug-at-bela, the con-
glomerate and gravel beds, well clad with grass vegetation, were seen to stretch far away
eastwards, and in a north-easterly direction across the Turug 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 seven miles, across a low pass at which a tributary of the Toyan 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. For this ridge the name Terek-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-west, composed at base of a tough limestone conglomerate of
younger tertiary origin, followed by white dolomitic limestone, 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 on the younger ones. North of Turug-at-bela the
range makes a sudden bend in an almost northerly direction, and continues to the Chaderkul,
where it forms the southern boundary of the lake-plateau. By this time the white dolomitic,
and afterwards the slaty beds, had 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 fragments is not distinguishable from the
Trias limestone 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 younger conglomeratic beds.

Across the Chaderkul 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 Chaderkul, 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
which appear to have taken place at the close of the kainozoic epoch within the southern
offshoots of the Thian Shan which we visited.

Short as our sojourn in the mountains was, it proved to be very interesting and equally
instructive. Humboldt's account of the volcanicity of the Thian Shan, chiefly taken from
Chinese sources, receives great support; but we must not speculate further beyond confiding
in the expectation that both meso and kainozoic rocks will be found amply represented
in it.

As far as our present researches in the physical aspect of the country extend, we
may speak of three geologically different ranges: the Terek range, which is the northernmost,
the Koktan in the middle, followed by the Artush range, below which begins the Kashghar
plain. All three decrease in the same order in their absolute height, the last very much more
so than the middle one. The first consists of old sedimentary rocks, the second of similar
rocks in its southern parts, while younger tertiary and basaltic rocks occupy the northern
portions, the third is entirely composed of young tertiary deposits. The general direction
of all the ranges is from west to east, or nearly so; this direction evidently dating from
the time when the whole of the Thian Shan chain was elevated. The undulating high plateau

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