CH. XI MILITARY BORDER EASTWARDS 191
In the following autumn I was able on my way back from explorations in the Nan-shan mountains to ascertain that the wall had its continuation eastwards along the Su-lo-ho as far as the great bend of the river from the south near the oasis of Yü-mên-hsien. This has taken its name from a later position of the `Jade Gate'.
But it was not until the spring of 1914 that my third expedition allowed me to carry my renewed systematic exploration of the Limes from Tun-huang right through to the Etsin-gol river, over a distance of some 32o miles. Where the Limes east of the oasis of An-hsi had been carried to the right bank of the Su-lo-ho and ran close to the deep-cut river-bed, its remains were less well preserved; because the prevailing north-east winds, blowing down with great violence from the gravel plateaux of the. Pei - shan and dreaded by wayfarers, could there assert to the full their destructive force of erosion on the loess soil of the bare riverine belt.
Still farther to the east the Limes line was found to have lain nearer to the foot-hills of the barren Pei-shan. Striking evidence was afforded here, too, of the persevering energy and power of organization with which those military engineers of the Emperor Wu-ti had faced formidable natural difficulties. Thus some thirty miles to the north-east of the little oasis of Ying-p`an (`the garrison') we found the line of the Limes boldly carried into and through what since ancient times must have been a big area of drift-sand. Where not completely buried by dunes the wall, built here wholly of tamarisk fascines and of the usual thickness, still rose to a height of close on fifteen feet. It was easy to realize what efforts it must have cost to assure water and supplies for
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