PHYSICAL FEATURES. 13 



Little need be said here about the process of formation of the sand- 

 hills, which has often been described and explained. 1 I have not 

 had an opportunity of seeing the longitudinal type of sandhill, found 

 along the western edge of the desert in the Thar and Parkar district 

 of Sind, but many of those that occur in the parts of the desert visited 

 by me are of an intermediate type. Several of these are well shown 

 on the one-inch maps of the neighbourhood of Balotra. 2 They ap- 

 pear to have been formed from hills of the transverse type by wind 

 denudation, the wind having scooped out furrows along the wind- 

 ward slope of the dunes. In the Barmer desert the sandhills are all 

 of the transverse type and well illustrate the tendency that dunes 

 possess of remaining permanent when they have reached a certain 

 height, for these dunes are all large, rising to 150 or 200 feet above 

 the plain, and have evidently, judging from the size of the trees 

 growing on their leeward slopes, remained in their present position for 

 many years. Further to the north-east, to the west of Jodhpur and 

 in Bikanir, the sandhills are not so high, and are constantly in motion 

 during the monsoon, but I have had no .opportunity of studying their 

 motion during that period. 



The rivers of this region play a very subordinate part in moulding 

 the surface features of the country. None of them, even near the 

 hills, contain perennially running water, and the beds of all of them are 

 so choked with sand, that the water, when floods do occur exercises 

 little or no eroding action on the solid rock. The Luni is the prin- 

 cipal river, taking its rise in the Ana Sagar at Ajmere and traversing 

 the whole of Marwar till it loses itself in the sands at the head of the 

 Runn of Cutch. It receives many tributaries from the Aravallis to 

 the south-east of its course, but none of any size from the more sandy 

 c ountry to the north. 



1 Blanford. Journ. As. Soc. Beng., Vol. XLV, Pt. 2, p. 86. 

 Walther. Denudation in der Wuste, Chapter V. 

 Vaughan Cornish. Journ. Roy Geo. Soc, Vol. IX, p. 288. 



2 Rajpulana Survey, Sheets 71, 72. 



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