GEOLOGY. 
25 
The southern slopes of the ridge are on their basal half entirely covered with gravel, 
which in places even extends to the top, assuming here a thickness of from 10 to 15 feet. 
Locally the gravel beds are separated from the main range by a shallow depression, forming 
a low ridge which runs along the base of the higher one, and from which it is, even in the 
distance, clearly discernible by its dark tint. The pebbles in the gravel are mostly of small 
size and well river-worn; they are derived to a very large extent from grey or greenish 
sandstones and shales, black or white limestone, more rarely of trap, basalt, and of gneiss. 
With the exception of the last-named rock, all the others had been met with in situ in the 
Upper Toyanda valley. The pieces of gneiss belong to a group of metamorphic rock which is 
usually called JBrotogine. It is mainly composed of quartz and white or reddish orthoclase, 
with a comparatively small proportion of a green chloritic substance. The white felspar 
variety generally contains as an accessory mineral schorl, in short, rather thick, crystals. 
I shall subsequently allude to the probable source from which the protogine pebbles might 
have been derived. 
Erom Artysh we marched, as already stated, northwards, up the Toyanda river, and for 
the next 22 miles one was surprised to find nothing hut the same Artysh and gravel deposits, 
the former constantly dipping at a high angle to north by west, and the latter resting on 
them in slightly inclined or horizontal strata; while among the recent river deposits in 
the bed of the valley itself the order of tilings appeared reversed. The gravels, having 
first yielded to denudation, here underly the clays derived from the Artysh beds, thus 
preparing an arable ground for the agriculturist, whenever a favourable opportunity offers 
itself. A few miles south of Chung-terek, the laminated Artysh beds entirely disappear 
under the gravel, which from its greater consistency assumes here the form of a rather tough, 
coarse conglomerate. In the bend of the river the latter has a thickness of fully 200 feet, 
and is eroded by lateral rivulets into remarkably regular Gothic pillars and turrets. It is 
rare to meet with a more perfect imitation of human art by nature. The general surface of 
the gravel deposits is comparatively low, from 400 to 500 feet above the level of the river; 
it is much denuded and intersected by minor streams and old water-courses. 
Koktan range. 
1. Gravel, occasionally hardened into conglomerate, 
ia. Limestone gravel. 
2. Yellowish and reddish sandy and clay beds (Artysh beds). 
3. Basalt. 
4- Tertiary sandstones and conglomerates, red or white, with bands of 
doleritic and greenstone rocks interstratified. 
sj. Bedded limestone conglomerates. 
6 . White dolomit'ic limestone, 
?. Dark semi-metamorphic schists and slates. 
8. Dark limestone. 
9. Blackish triassic limestone. 
10. Triassic ? greenish shales below the limestone, 
n. Palaeozoic shales, slates and sandstones. 
12. A band of white and reddish crystalline limestone. 
Section from Kashghar to the Chadyr lahe. 
At a couple of miles north of Chung-terek the Koktan range begins with rather abrupt 
limestone cliffs, rising to about 8,000 feet above the level of the Toyanda. Nearly in the mid- 
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