APPENDIX A
GEOLOGICAL AND MINOR GEOGRAPHICAL CONSIDERATIONS IN TIBET AND TURKESTAN
Partly from a Paper read before the Royal Geographical Society, February 8, 1904.
WRILE ascending the mountains from Polu, one sees rapidly at work the forces of disintegration attacking the vast masses of exposed friable material. Slates, shales, conglomerates, loose sandstones—such are the abounding substances which the torrents wear away. One also sees some large pebbles of the harder materials scarcely to be found now represented by the strata above them in situ. Great as are these changes now, they must be pigmy efforts compared to the titanic movements of the past. On the plateau one sees and travels in veritable rivers of sand ; its large limits mark the boundaries of some great slow stream whose waters came down from vanished heights. Again, where the slope is greater, the course of a mighty torrent is marked by close-packed, rounded boulders. In one case, we followed the bank of such a silent river of stones to an elevation of eighteen thousand feet, where a flat area about three miles long showed boulders laid so accurately to the level, so cemented by sand, sometimes so regularly formed in circles, that one would have thought it a pavement of giants leading to the foundations of huge temples. Save, perhaps, in some stretches of the upper Blue Nile, I have never seen a stream having at the same
274
IIIF Color HighRes
