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. 

 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 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. For 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 on the younger. 

 North 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 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 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 



