We were tempted to follow bajir No. 36, for without doubt it would have given us a good help along our road; but, as it did not run in our direction, we left it alone, and turned our steps up into the sand, and were soon rewarded by finding bajir No. 37, which not only ran in the direction we wanted to go, but was pretty large. It gave the impression of an elongated arena fenced in by high sand. and the threshold at its south-south-west extremity appeared to be unusually low in elevation. In respect of its vegetation this bajir was like those we had just traversed, but its western half was filled with small dunes, which increased in size the farther west they were situated, until finally they became merged in the windward flank of the fresh chain of dunes which started there. But the eastern half of the bajir was perfectly free from sand, and it was there that the vegetation had especially got a good foothold. True, there was sand amongst the bushes, but there were no dunes. Thus in bajir No. 37 there was no clay soil exposed, not even so much as one square meter. Consequently from bajir No. 3o inclusive the ground consisted of sand, and yielded vegetation, and the ground-water was fresh; whereas in all the bajirs before No. 3o the ground had consisted of saliferous clay (schor), was devoid of vegetation, and yielded water that was salt. Certain enterprising scrubby plants had actually established themselves on the lower slopes of the steep eastern wall, even as high as I o to 15 m. above the floor of the bajir. Now though this indicates a very slow advance on the part of the dune-wall, it does not by any means mean that the latter stands still, for these plants, which love to have their roots amongst the sand, possess, like the saksaul, the ability to »swim», as it were, on its surface; and even when a part of the plant becomes buried under the sand, a new shoot springs up, and the roots are lengthened. They are, as it were, the water-lilies of this sandy ocean, and float on its waves. Yet many no doubt perish in it all the same.
Here too another structural formation began to appear. It is shown in section in the above illustration (fig. 273), and consists of a series of ridges or swellings, in most cases very narrow and not more than one or two centimeters in height, which stick out on the windward side of the individual dunes, that turn their steep leeward side towards the west-south-west, and form as it were a sort of ribbing on it parallel to the existing crest. It soon became apparent that they had previously each in turn been the actual crest of the dune. A closer investigation showed that the sand of which they are composed is closely packed together, and is hard and cohesive, so that small fragments can be chipped off it, though it requires but little force to make them crumble to pieces again. Still their cohesiveness is sufficient to prevent the individual particles of sand from falling asunder, as they do elsewhere. What prevents them from
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