OVER THE ARA-TAGIL AND TIlE KAL'L'A-ALAGIIAN.
appear to have come from the west. Nevertheless the steep and frequently irregular shape of the dunes suggests that the east wind also prevails during a part of the year. Both the orographical relief and the direction of the latitudinal valley render it probable that the east and west winds are the strongest, and the sharpness with which the drift-sand area comes to an end likewise indicates that the winds from these two predominant directions are about equal in point of strength. Hence this sandy area is stationary, like the Kum-tagh south of Pitschan, and within its area the dunes travel, over a limited distance, backwards and forwards, and not exclusively in one direction like the dunes of the Desert of Lop. Meanwhile the sand goes on accumulating within its area, and the dunes gradually increase in height, the material being derived from the disintegrating mountains on the east and the west.
Animal life was represented by kulans, of which immense troops were grazing all over the scattered patches of grass. The other animals consisted of marmots (davaghan) and hares of a steel-grey colour with white under-parts.
The only places in which we observed the hard rock were in two or three promontories of the Kalta-alaghan at the beginning of the day's march, namely a grey granite, strongly inclined to pink, and with moderate-sized grains, as well as green porphyry; and the gravel which in places littered the bottom of the valley consisted
for the most part of the same rocks.
Fig. 50. THE CAMP AT BULAK-BASCHI.
IIIF Color HighRes
