than that of the Western Nan-shan or of the K'un-lun. It indicates
n the vicinity of the Pacific drainage area which extends to the adjoining
parts of Kan-su and of the north-eastern uplands of Tibet. Abundant vegetation clothes the valleys from the westernmost limits of the Pei-ta-ho or Su-chou river's drainage i and makes the big open troughs at the headwaters excellent summer grazing grounds, notwithstanding their great elevation, above 11,000 feet, and Pamir-like appearance. Further to the south-east increasing snow and rainfall permits of plentiful forest growth in the valleys of the Richthofen Range draining into the Kan-chou river. 2
Along the northern foot of this range at an elevation of about 5,000-6,000 feet, stretches a broad belt of fertile alluvial fans, separated in places by scrub-covered Cultivated area N. of table-lands. 3 Its northern limit is formed by the barren hill-chain
overlooking the middle course of the rivers of Kan-chou and Su-chou, and belonging to the Ala-shan system of southernmost Mongolia. Over great parts of this second region, cultivation is assured by abundant irrigation from the rivers and also by the fact that from about the longitude of Kan-chou city eastwards, climatic conditions along the fertile foot of the Nan-shan permit of cultivation dependent on snow and rainfall only. Hence we find in this region not only large and populous oases occupying the alluvial fans of the Su-chou and Kan-chow rivers, but also an almost continuous chain of smaller village tracts skirting the foot of the mountains beyond those fans.
The physical features here briefly indicated have made this region historically a very important land of passage ' between China and Central Asia. For the
marches s of ba en. Chinese its possession was indispensable in economic and military
respects ever since their policy of Central-Asian expansion more than two thousand years ago first opened the route through the north-western marches of Kan-su and along the Su-lo-ho into the Tarim basin. But before their advent and during the periods when their control of the route ceased, the abundant winter grazing which parts of this region afford, made it also for centuries a goal of conquest for a succession of nomadic nations. 4
A region of very different character stretches from the barren hill-range north of the chain of oases down to the terminal basin of the Etsin-gol. We find
Cultivated areas on there, indeed, two narrow strips of cultivation, those of Chin-t`a and Etsin-got.
Mao-mei, lying beyond the gorges in which the rivers of Su-chou and Kan-chou, respectively, have cut their way through that range. 6 But apart from them the whole of this region consists of desert ground, affording now but limited grazing in the delta which the Ehkin-gol forms from a point about 60 miles below the lower end of Mao-mei cultivation. 6 Amidst the almost waterless valleys and plateaus which adjoin the Etsin-gol on the east and west, even camel grazing is scanty and confined to rare patches of ground.
Nevertheless, the Etsin-gol valley has always possessed considerable importance as a
highway for nomadic migration and trade from Mongolia into north-
western China. It resembles in this respect the territory of ancient
Lou-lan, now completely abandoned to the desert, and this affinity is
I Near the T'a-ta.fan, Sheet No. 41. D. 1.
2 See Sheets Nos. 43. D. 3, 4; 46. A. 3, 4, B. 4, C, D.
s See Sheets Nos. 43 A-D.1,2; 4ß, A. 2, B. 2.3,C. 3,4.
4 Cf. Serindia. ii. pp. 1131 sq. Such grazing is to be found -in plenty along the lower courses of all. rivers that drain the northern slopes of, or pass through,.the Richthofen range, It 14 not altogether
absent even in the tracts of drif1:-and to be met with between them; see Sheet. No. 41'. e, D. 1, 2.
6 See Sheet N 42. 4.
6 See Sheet Ne. 45. 11. 2.
7 Cf. 7'hird Journey. Geogr. Journal, xlviii. pp. 197 eq. For the site of lihara-khoto, Marco Pelo'a ' City of Etzina', see Sheet No. 45: 0, L'.1.
e Cf. above pp. 31 sq., 47.