Change of A striking change, however, came over the ground on ascending towards the Tu-ta-fan from
cliimaticns the gravel plateau beyond the Po-yang Ho.c The broad valley leading up to this pass, the western-near T`u-ta- most of those which cross the Richthofen Range proper, proved to be clothed with luxuriant grass
fan. and flowers that recalled true Alpine vegetation: It was the first, but sharply marked, indication
of the distinct change in climatic conditions which was subsequently observed right through the Nan-shan ranges south-eastwards and, in a lesser degree, also in the submontane tracts adjoining them on the north. We were here leaving behind the extreme south-eastern limits of the great arid belt of innermost Asia, as represented by the Tarim Basin and the adjoining drainageless areas, and were entering that westernmost portion of true China which, remote as it is, is affected in its climate by the increased moisture passing up from the Pacific.
Physical It is important that we should realize clearly the meeting at this point of two great physical
divisions divisions of Asia ; for this geographical fact has had its manifest bearing upon the position of what
Cliayi! has been the recognized main western entrance into China for the last five hundred years, if not
kuan. longer. I mean the famous Gate of Chiayü kuan, the modern representative of the ancient Jade
Gate. Its distance from the debouchure of the Tu-ta-fan valley is less than twenty-five miles, and the contrast between this verdant alpine vale and the arid wastes of the Nan-shah beyond it to the west is scarcely more striking than the change experienced by the traveller as, having crossed a vast stony steppe from the west, he reaches the ` Great Wall ' and, through the Gate of Chia-yü kuan, passes into the succession of fertile tracts within. My own approach to this western end of the ` Great Wall ' was singularly adapted to bring out the big features of its topographical setting. So I may well briefly describe it before discussing Chia-yü kuan itself.
First sight I had my first sight of the Great Wall, and a very impressive one, when after descending from
Wall'. at T`
W' the Tu-ta-fan I rode on the evening of July 18 along the fantastically eroded foot-hills of the Nan-
shan eastwards to the hamlet of Ta-han-chuang.7 To the north an utterly lifeless steppe of stone and gravel, fully twelve to fifteen miles wide, was seen to separate this fringe of the snowy Nan-shan from a terribly bare hill range running parallel to it and forming a south-eastern offshoot of the Peishan. As I looked down from a height of close on 8,000 feet, the view ranged unbroken along this vast valley or plateau eastwards. Far away in the distance low gravel ridges, marking the watershed towards the Pei-ta Ho, seemed to form an eastern rim of the plateau. Along this the setting sun lit up a long-stretched faint streak of white—the line of the ` Great Wall '. The distance separating me from its nearest point was still close upon twenty miles. But in the clear atmosphere it was possible to make out towers reflecting the slanting rays and, stretching away to the horizon beyond, a great expanse of dark ground. It was the fertile district of Su-chou with its green fields and arbours. Set off clearly against the grey of the steppe and the red of the bare desert hills, it made me realize with my eyes what China ` within the Wall ' (kuan li-t`ou) meant, and why its border was drawn here.
Approach The little fortified post of Ta-han-chuang (Fig. 251), which I visited next morning, was tenanted
to Gate of by a few soldiers as an outpost of Chia-yii kuan to watch the route along the foot of the mountains. Chia yii
kuan. Its massive watch-tower and the small walled enclosure adjoining, both half-ruined, seemed an apt
illustration of what posts on the ancient Han Limes might have looked like, though in a far more desolate setting. The same day a long weary march brought us transversely over the bare stony ` Sai ' of the valley to a point on the high road about four miles west of Chia-yii kuan. All view of the wall and its great Gate had vanished in the glare of the day. Instead there loomed before us the eastern extremity of the long barren range already referred to as overlooking the valley from the north. A glance at its steep serrated ridges, furrowed by a maze of narrow ravines, sufficed to
6 See Map No. 86. D. 2 ; Desert Cathay, ii. Fig. 220. 7 See Map No. 86. n. 2.