of Chib-chang-tso, traversed by BONVALOT and ROCKHILL, and still farther east it merges into the mighty Tang-la system. Much of the deduction given above is conjectural, but still it seems very probable that the Kara-korum Pass is situated in the same series of crustal folds as is the mountain system which in the east of Tibet is called Tang-la.
The Aghil Range which is the next fold in the series, is more difficult to determine than the Kara-korum folds. BURRARD says of it : »But little is known of the Aghil range; it was discovered by Sir Francis Younghusband, and a few of its peaks have been observed by surveyors ; but its length and direction have not been determined. The position given to it on the frontispiece to Part I and its junction with the Sarikol range are conjectural. The peaks observed between the Kuen Lun and Karakoram ranges along the upper courses of the Yarkand river appear to be scattered rather than aligned, and the region seems to resemble in complexity that between the Indus and Kunar rivers.— It may be that the Kuen Lun , Aghil and Kara-korum folds have been pressed against one another; all the ranges of Tibet tend to converge at the north-western corner of the plateau , as though they were trying to escape through the neck of a bottle; once having passed the neck they separate again, but during the passage they appear to suffer from extreme corn-pression.» I
So much is sure; that an Aghil fold exists in the north-western corner of the Tibetan highland, and it probably continues through the whole of Central Tibet. But another matter is to determine the connection between YOUNGHUSBAND's and BURRARD's Aghil Range and the prolonged system of folds running just north of the North Kara-korum system. For instead of a continuous range or system of ranges, we come across the interruption caused by the plains of Ling-shi-tang and Aksai-chin, which in the region east of the upper Kara-kash occupies the entire space between the North Kara - korum and the Southern Kwen - lun. It is therefore only by conjecture that we may try and find a connection between the folds west and east of the plateau plains. The Aghil Range itself is crossed by th& Karakorum road and pierced by the upper Kara-kash River, though with our present knowledge it will be difficult to tell where these intersections take place. I have the impression that the Aghil Range is double even before reaching the meridional valley of the upper Kara-kash. The latitudinal valley which I followed from the Dapsang Pass eastwards in the last days of December 1907, crosses the southern range and is in its eastern part situated between both ranges. East of the uppermost Kara-kash the southern range has two peaks of respectively 6388 and 6308 m., probably measured by Indian surveyors. After the interruption of Ling-shi-tang,
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