THE TIAN SHAN MOUNTAINS. 
73 
steppes north of the Hi River; and that the present relief of many of the higher 
Tian Shan ranges is the result of a somewhat disorderly uplift and of a more or less 
complete dissection of dislocated parts of the worn-down region. Mr. Huntington's 
report .shows the application of these conclusions to a large part of the central and 
southern Tian Shan. 
THE BURAL-B.\S-TAU. 
The first range that led to this belief was the Bural-bas-tau, which rises north 
of the Narin \'alle\- and southeast of Son Kul. Its name is taken from the Russian 
40-verst map. Friedrichsen (1899) calls it the Mulda-aschu. We saw the range 
some 50 miles away as we were riding down the Alabuga \'alley on July 4 ; the 
Fig. 40. — The Flat-Topped Bural-bas-tau, looking Southeast. 
evenness of its snow-covered crest suggested that it nuist be a plateau-like mass of 
horizontal structure, amid its deformed neighbors. It was lost to sight after we had 
entered the Narin \"alley, and was not seen again until July 9, when we climbed 
the Kok-tal range northeast of Son Kul. It was there that figures 40 and 41 were 
Fig. 41. — The Flat-Topped Bural-bas-tau. looking South. 
sketched. The e\-enness of the plateau-like highland, all snow-covered at an estimated 
height of at least 12,000 or 13,000 feet, was most remarkable, and all the more so as 
our field-glasses now showed the range to be composed of massi\-e rocks, probably 
granites, such as are plentiful thereabouts. The highland has faint undulations, 
and slopes gently to the north and east. Great ravines, heading in glacial cirques, 
are car\'ed in its northern flank. The spurs between the ravines preserve their even 
crest for a short distance, but are then converted into sharp aretes. One ravine, 
longer than the others, cuts the highland obliquely. It reminded us of the Colorado 
Canyon in the Kanab plateau of Arizona, as we had seen it from the top of Mount 
Trumbull in the sunnner of 1902. One ravine-heading cirque, opening northward, 
seemed to head against another, opening southward, and there the even highland 
surface was reduced to a serrate ridge that sagged a little below the general level. 
The highland ascends gradiialh- westward, and in that direction its detached por- 
tions, with flat tops, are seen beyond encroaching \alleys; then, still farther west, 
these arc succeeded by peaks and ridges of ordinary fonn in the Dongxis-tau range 
south of Son Kul. 
