2l6 VREDENBURG: SKETCH OF BALfJCHISTAN DESERT. 



given of similar formations by many authors. Of the two kinds of 

 sandhills distinguished by Mr, Oldham in the Indian desert, 1 only 

 the " transverse" type is exhibited in the localities which I have 

 visited, while the cresent-shaped dunes called " barchanes ° or 

 "medanos" are everywhere developed with the most typical charac- 

 ters. 2 Sometimes the dunes coalesce into huge masses which are 

 slowly advancing over the plains, and against which even the moun- 

 tains no longer form a barrier : the sand is blown over the crests of 

 the ranges and many a valley is being buried beneath a shroud of 

 sand. Entire ranges of low hiils have already been buried in the 

 region between Amir-Chdh and Saindak where some of the sand- 

 hills rise to heights of as much as 200 feet. The sandhills when 

 newly-formed at least are extremely permeable ; for instance, at 

 Amir-Chah there is a river-bed which cuts through the hill range 

 forming a narrow gorge or "tangi," beyond which it is cut across 

 by a broad belt of sandhills. Some ten miles further the river-bed 

 once more re-appears from beneath the sand dunes. It is joined by 

 several tributaries, one of which bears the name of Sam river, and 

 finally finds its way to the Gaud-i-Zirreh. On one occasion while 

 I was at Amir-Chdh in the night of the nth to the 12th of March, 

 there was a heavy shower of rain which converted the dried up 

 stream-bed into a raging torrent. On the following morning, 

 Mr. Tate went to see whether the sandhills had kept back any body 

 of water where they cut across the river-bed ; but this place was 

 perfectly dry, notwithstanding that small pools had been left in other 

 portions of the river-bed. I ignore whether any flow of water 

 appeared from beneath the sand where the river-course once more 

 comes to light. 



» Manual of the Geology of India, 2nd edition, p. 455. 



3 The question of sand dunes has been studied both from a theoretical and an ex- 

 perimental point of view by Vaughan Cornish: "On the formation of sand dunes." Geogr. 

 Journ., Vol. XI (1897), pp. 278-309. For descriptions of the sand dunes in the Baluchistan 

 desert, see Pottinger, " Travels in Baluchistan and Sinde," p. 132; McGregor, " Wander- 

 ings in Baluchistan/' p. 157; C. L. Griesbach, Rec. Geol. Surv. Ind., Vol. XVM (18S5), 

 P- 59- 



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