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44

72   NOTES ON INDIVIDUAL MAP SHEETS   [Chap. IV

topographical details concerning Mr. Johnson's Yangi-dawan and his route beyond towards K aranghu-tagh, see my note on Johnson's map and the topography of the K`un-lun south of Khotan, in the Alpine Journa1,1921, xxxiv. pp. 62 sqq.

Limited as the actually surveyed area within• this sheet is, it includes three well-marked portions of distinctive character : utterly sterile basins characteristic of the extreme north-west of Tibet; the main Kunlun range with its deep-cut valleys draining northward into the Yurung-leash river, and the high open plateaus between the Kara-

NOTES ON SHEET

The survey shown in this sheet is confined to the vicinity cf the route leading from the south to the Muz-art pass on the main Tien-shan range, and to a small portion of the outer hills above the tract of Kara-bagh. The plane-table work of R. B. Lal Singh was adjusted to the position adopted for the Tengri-khan Peak in the map accompanying Dr. Merzbacher's The Central 'Pian-slran Mountains, London, 1905, and to the plotting of the adjoining sheet No. 12.

The heights shown for Tengri-khan and

koram and the tiara-kash river.

Corrections. D. 1. The ascent up the glacier at the head of the Turgap valley (Sheet No. 9. D. 4), to about long. 79° 42' lat. :35° 59', ought to have been indicated; cf. Desert Cathay, i. 200 sq.

D. 2. The approximate position of Mr. Johnson's Nai{ Kh{n-dawan' may conjecturally be placed at about long. 79° 46' lat. 35° 58'.

D. 2. Peak 8152MM (23,309) has not been shown on the map according to its computed longitude 79° 51' 0"; see Appendix A, points in 52M.

No. 11 ( MUZ-ART )

another high snowy peak sighted from the route are taken from Dr. Merzbacher's map in the Central Tian-span Mountains. So is also that of the Muz-art pass, the summit of which the surveyor was unable to reach owing to the heavy snow encountered. His visit took place in the first half of May when the snow still lay low, and on this account the approximate level of the snow-line and the extent of the glaciers shown are subject to doubt.

NOTES ON SHEET No. 12 (KARA-YULGHUN, BAI )

Of the routes falling within this sheet only those from the terminal course of the Khotan river to Ak-su and north-east of this town were followed in 1908; the rest were all surveyed in 1915, that along the foot of the mountains by R. B. Lal Singh, the one between Bai and Ak-su by myself, and the two further south by surveyors Afraz-gul and Muhammad Yakûb, respectively.

The plotting of the sheet is based on the positions adopted for Ak-su and Kucha in Sheets No. 7, 17 and on that for the junction of the Ak-su and Yarkand rivers. For the latitude of the last the value observed by Dr. Hedin, viz. 40° 28' 47", was used, while the longitude adopted is the mean between the values obtained by interpolation between Kashgar and Korla and between Khotan and Ak-su. Latitude observations taken by Dr. Hedin were utilized for a number of points on the Tarim river. For Muhammad Yaknb's traverse along this river, a check on longitude was afforded also by the position of Peres

(Sheet No. 17. B. 2), where the former is crossed by the desert route from Kuehl'', to the Keriya river. Similarly the adopted position of Tengri-khan (see Notes on Sheet No. 11) was used for the adjustment of the route leading from Ak-su to the Muz-art pass.

In the northern portion of the sheet lies the subordinate basin of Bai ( C, D. 1 ), enclosed between the foothills of the main Tien-shan and a much-eroded outer range. The Muz-art river and some of its tributaries supply irrigation to considerable tracts in this basin. The same is the case with part of the submontane area between Ak-su and Jam (A. 2) which receives water from the snowy main range. The large volume of the Ak-su river renders irrigation possible along both its banks for a considerable distance.

Between the foot of the above mentioned outer range and the jungle belt accompanying the Tarim 'stretches an area of scrubby desert. The existence of certain