THIRD EXPEDITION, 1913-15 31
Bèsh-toghrak. 2s Extending over a distance of 60 miles it has proved a continuously descending slope with a total drop of 25() feet from the latter point.
Coupled with other observations, the result of this levelling has confirmed the belief
formed on my passage in 1907 that the waters of the Su-lo-ho at a period relatively recent in a geological sense had drained into the Lop basin. 29 In this connection the fresh surveys effected in the
desert area which lies east of Besh-toghrak and north of the present terminal basin of the Su-to-ho, proved of special geographical interest; they showed that its depressions still receive subsoil drainage from abandoned branches of the Su-lo-ho delta, and that its mazes of Mesas are those typical of all lacustrine basins in this region. 3e The importance of the connection thus traced here between the drainage area of the Tarim which has its western limits on the Pamirs, and that of the Su-lo-ho which extends as far as the watershed of the Pacific Ocean, fully 24 degrees of longitude further east, scarcely needs to be emphasized.
Leaving Lal Singh and Muhammad Yakùb behind for supplementary surveys within
the present terminal basin of the Su-to-ho, 31 and along the river's course between it and Lake Khara-nôr, I proceeded to the vicinity of the latter along the line of the ancient Chinese Limes first discovered
by me in 1907. From there I completed my detailed exploration of the Tun-huang Limes on ground stretching eastwards which circumstances in 1907 had obliged me to leave unsurveyed.
. A brief halt was necessary at Tun-huang during the last days of March to allow men and animals to recover from the trials of our winter campaign. Then we
Survey in westernmost separated once more. While I paid a fresh visit to the famous cave
Nan-sham. P 1
temples of the Thousand Buddhas,' or Chien-fo-tung, south-east of Tun-huang, not without archaeological profit, Lai Singh proceeded to the mountains due south. Owing to deep snow he was obliged to content himself with surveying the northern slopes of the westernmost Nan-shan near the debouchure of the river of Tun-huang or Tang-ho, before re-joining me by the middle of April at An-hsi via Tung-pa-t`u and T'a-shih. 43 Muhammad Yakûb was sent north of the Tun-huang oasis by a new route and then mapped the Su-lo-ho river along a previously unsurveyed portion of its course to An-hsi.
The task I had set myself for the spring was to trace the line of the Chinese Limes of Han times from Tun-huang as far as possible to the east and to
Ancient Limes traced to explore whatever ruins might have survived along it. I commenced
and beyond An-hsi. P b along
this task by skirting across a belt of difficult salt marshes into the desert north-eastwards of Tun-huang. At a point not far from where our exploration of 1907 ended, I came again upon the ancient border wall and traced it thence through to An-hsi. 3} From there, accompanied by Là1 Singh, I moved up the right bank of the Su-lo-ho and found further remains of the Limes wall and its watch-towers opposite the low hills of Wang-shan-tzu, exactly where our survey of 1907 carried along the left bank of the river had led me to look for them. 35
The search for the ancient defensive line which at the end of the second century B.C. had been raised to protect China's great line of communication into
Survey to east of Central Asia from Hun raids was now successfully continued to the
sharp southward bend of the Su-lo-ho southward. Here near the small village of Shih-êrh-t`un we touched the easternmost point at which on my previous expedition I had-been able to trace remains of the Limes line. 36 The more careful survey of the
Connection of Su-lo-ho
and Lop basins.
Chinese Limes eiplored to Tnn-hnang.
se For a chart recording the result of this levelling see Appendix C. There information has also been given as regards the value to be attached to the elevation which has been accepted for the starting point of the levelling at Camp xcvm; see Sheet No. 32. D. 4.
39 See Desert Cat1 ay, i. pp. 535 sqq; Serindia, ii, pp. 661, sq.
3° See Sheet No. 35. B, C. 3, 4.
31 See Sheet No. 35. B, C. 4.
s= See Sheet No. 38. A, B. 4.
33 See Sheet No. 38. B, D. 4; 39. B-D. 1.
$4 See Sheet No. 38. B, C. 4.
33 The point where the Limes line coming from the east was carried across the So-lo-ho to the left bank which it thence followed right through to t h river's terminal basin is marked in Sheet No. 40. A. 3 by the ruined watch-towers T. xn, a-c.
as See Sheet No. 40. C.4.