of loose sand, advancing in regular wave lines from north-west to south-east. The sand dunes are mostly from ten to twenty feet high, but some are seen, like little hills, full a hundred feet high, and in some spots higher, They cover the plain, of which the hard clay is seen between their rows, with numberless chains of two or three or more together in a line, and follow in successive rows one behind the other, just like the marks left by wave ripples on a sandy beach, only on a large scale. Towards the south-east these sand dunes all present a steep bank in the shape of a crescent, the horns of which slope forwards and downwards, in points, to the ground . . . ." The process of submergence, Dr. Bellew found to be usually a very gradual one, until the symmetry of the dune, becoming broken by an obstructing object, its loose materials subside, and thus overwhelm the obstruction. In the instance of one of the buildings inspected, it was found that "a chain of three crescentic dunes, side by side, had advanced in line across the plain, till one of the outer crescents had struck the walls of the court of the tenement, and growing up, had, in time, over-topped, and thus overflowed and filled its area by its downfall ; whilst the other two crescents at its side, continuing their unobstructed course, maintained their proper form uninjured."[1] The rate of progression the writer was unable to determine, as it depends on the varying force of the propelling power, the slope of the land, and the obstructions on its surface. The operation, however, is the same as in the well-known instance of Eccles church, on the coast of Norfolk, only on a larger scale. By 1839 the whole of the church, except a portion of the tower, had been buried; by 1862 the tower had nearly emerged again, while in 1892 the whole building rose free from the level of the strand, the dunes having passed to its landward side.
The phenomenon thus seen in operation, explains how the town of Katak, and others mentioned by Mirza Haidar, became engulfed, and confirms the stories still current in Eastern Turkistan of ruined towns, or buildings, now and then appearing for a while and being again submerged.[2] In the extreme east of the country, the sandy desert is found at its worst, and it is in connection with this quarter that most of the tales of weird horrors have their origin. How deeply the superstitious
