182 JOURNAL, BOMB A Y NATURAL HISTORY SOCIETY, Vol. Xll. 



Medlicott's " Geology of India," there are in Sind two types of sandhills — one 

 lying transverse to the prevailing winds and the other parallel to them, the 

 direction here being about 30° south of west. Now it is only necessary to 

 study the drifting of snow to see that, while comparatively gentle winds make 

 transverse drift, the snow that is borne along tumultuously by the wind lies, 

 when the wind drops, in long straggling lines parallel to the course it has taken. 

 These longitudinal sand-dunes therefore indicate a great velocity of wind 

 in the desert north of the Ran, so that we ate not surprised to learn that 

 some of them, even without the aid of any inclined plane of solid rock below 

 are able to attain a height of 400 to 500 feet. That the same phenomena 

 are found in Cutch itself may be <:athered from the fact that, in speaking of 

 the sand-dunes along the southern coast, Mr, Wynne says that they have a 

 bearing of about 20° south of west, ^ which is exactly the average direction, 

 as seen above, of the strongest winds. From personal observation I can only 

 say that at Mandvi, after the close of the monsoon season, when the sea had 

 calmed down enough for steamers to call, the wind was constantly blinding 

 with sand, and the pier was all buried in a dune. That large areas of Cutch 

 are now covered with still drifting sand is pointed out by Mr. Wynne. - 



The cause assigned being thus found adequate for the work, we must next 

 enquire how far it explains the special phenomena noted above. As it was 

 the distribution of the deposi+s that suggested the cause, this must be taken 

 first. Now all the localities may be described as spots where a wind coming 

 from the west or south would be stopped by an obstacle, or where a shelter- 

 spot exists in a long scarp. Thus in the Kala Dongar the wind would be 

 stopped by ?. projecting high land, below Koha Hill by a watershed, below 

 Bhujia Hill by the hill itself, between Ler and Jadura, and also North-Wes- 

 tern of Godpur. by projecting dykes, and on the Mandvi road by the Jurassic 

 escarpments. On the other hand shelter-spots occur above Andhou on the 

 Gora Dongar, on the flanks of Habo Hills on the Kas scarp, on the south 

 side of the Jhurio Hills, and at Khedoi on the trap-escarpment. In some 

 other places, as along the north side of the Katrod Hills, and apparently at 

 Baukha, the deposit makes no feature on the surface, being level with the 

 ground, and thus probably fills originally existing hollows. To this latter 

 catef^ory must also be assigned the various glens in which the deposits less 

 abundantly occur. 



It is thus seen that ihe horizontal distribution is exactly what it ought to 

 be. In the vertical direction, where the deposits occur at high levels inland, 

 the main valleys are also high, so that there is not a great difference of level; 

 but in the case of the Gora Dongar, where the deposits are 560 feet above 

 the neighbouring Kan, there is a gradual rocky slope all the way, leading up 

 to the hollow where they lie. In the case of the Kas scarp the west wind 



' Mem. Geol. Surv. ludi;i, vol., ix. pt. i. (1872), p. S2. - Ih'id, p. 12. 



