Sec. i] TO THE GATES OF THE ' GREAT WALL' m7
show that it must have served at all times as a great natural flank protection for the route towards An-hsi and Central Asia \vhich skirts its foot for three marches. Not far from the point where we struck this high road a small valley, known as Hao•shan-k`ou,s receives the subsoil water from the Nan-shan, which comes to the surface here and cuts through the south-eastern end of the range. Some large towers perched on low spurs seem intended to guard the approach to it. As I followed the narrow cart track leading towards Chia-yü kuan, I felt that I was on historical soil ; for there can be no question that it was this very line, the most direct and convenient connecting Su-chou with An-hsi and Tun-huang, over which all Chinese enterprise, military, political, commercial, towards the ` Western regions ' must have moved for over two thousand years.
After four miles of gentle but steady rise over stony waste, the top of a broad ridge was reached which bears at its eastern edge, and on a level about 8o–roo feet lower, the closing fortress and
wall of Chia-yü kuan 144 0. The high storied towers over the inner and outer west
gates (Fig. 249), built of wood, first came into view from a distance of about two miles ; then, on closer approach, also the wall of stamped clay extending from either flank of the massive square fortress which guards this gate of the 'Middle Kingdom '. On the south, its line could be seen stretching away for a distance of about six miles to where Pei-ta Ho, or Su-chou River, skirts the foot of a projecting buttress of the Nan-shan (Fig. 250). Northward, the wall soon becomes hidden by the scarp of the ridge on which we stood. But some four miles off its line could be picked up again ascending a rugged spur above the north-eastern end of the Hao-span-k`ou gorge. Eastwards, the vista from the ridge ranged far over the vast plain that slopes gently down towards Su-chou and is green with fields and trees.
Standing on this commanding edge of the plateau it was easy to see—and the map shows it, too, with almost equal clearness—that if a barrier had to be drawn across the great natural route from the west to close approach by it to the long stretch of cultivated tracts along the foot of the Nan-shan, no better position could be chosen than this. Nowhere else was it possible to guard the broad valley between the foot of the snowy range and the desert hills of the Pei-shan with such ease. On this line the two approached within less than eight miles of each other, and excellent natural protection was provided on either flank, by the Pei-ta Ho on the south and the precipitous and practically impassable ridges northward. For a border policy which aimed at strict seclusion involving passive defence—and that this was in full force when Chia-yu kuan first comes into notice we know from history—there were obvious advantages, too, in the utter barrenness of the stony glacis in front, stretching westwards for more than twenty miles, and in the abundance of local resources immediately behind the protected line.
But while the eye took in easily the sound topographical reasons for selecting this position. for the barrier, the distant and clear view from that ridge revealed also what seemed an archaeologically puzzling observation. Quite distinct from the line of wall before me that ran with an approximately north-western bearing towards the debouchure of Hao-shan-k`ou, another line of wall and towers, less well preserved but still unmistakable in its alignment, was seen to stretch far away to the northeast. I knew well that all books and maps, whether Chinese or European, made the ' Great Wall' which protects the northern border of Kan-su terminate in an imposing line which bent round the westernmost portion of the Su-chou district to the very foot of the Nan-shan. But the wall which was now seen to run, as the map (No. 88. B. I) shows, in the direction-from south-west to north-east did not look like a continuation of the barrier extended on either side of Chia-yii kuan. It manifestly