86 W. T. Blanforcl — On the Physical Geography [No. 2, 



IX. — On the Physical Geography of the Great Indian Desert with especial 

 reference to the former Existence of the Sea in the Indus Valley ; 

 and on the Origin and Mode of Formation of the Sand-hills. — By 

 W. T. Blanford, F. B. S. 



(Received June 31st; — Eead July 5th, 1876.) 

 Contents. 



§ 1. Introduction. — Geological distinction between the Indian Peninsula and the 



neighbouring portions of Asia. 

 § 2. Zoological Relations between India and Africa. 



§ 3. The Indo-gangetic Plain between India and the adjoining regions of Asia. 

 § 4. Physical Characters of the Desert. Botany and Zoology. 

 § 5. Distribution of the Sand-hills. 



§ 6. Evidence of subrecent Marine Action. Salt ' dhandhs.' 

 § 7. Marine Mollusk living in Salt Lakes. 



§ 8. Former existence of an Inlet of the Sea in Eastern Sind. The Ran of Kachh. 

 § 9. The Luni Basin. 



§ 10. "Want of evidence of Marine Denudation elsewhere in the Desert. 

 § 11. Nature and Origin of the Sand-hills. 

 § 12. Source of the Sand. 

 § 13. Conclusions. 



§ 1. Introduction. — Geological distinction between the Indian Penin- 

 sula and the neighbouring port ions of Asia. — There is no tract of country in 

 India more singular in its character than that which is commonly known as 

 the Great Desert, lying on the eastern side of the Indus between Sind and 

 Eajputana. The peculiar nature of the region has often been described, but 

 there are still some points in its physical geography which appear to require 

 explanation, and which are not, I think, entirely cleared up in the best ac- 

 count of the region with which I am acquainted, that given by Sir H. B. 

 E. Frere in the Journal of the Boyal Geographical Society for 1870, Yol. 

 XL, p. 181. To these points, which chiefly refer to the origin of the sand- 

 hills, I shall advert in the sequel. 



The physical geography of a country is always intimately connected 

 with its geological construction and history, and from this point of view 

 the Great Desert is a tract of peculiar interest. It is almost a truism at 

 the present day to state that India proper has no geological connexion with 

 the surroimding countries. The whole geological history of the Indian 

 peninsula, from the date of the earliest sedimentary formations, shews 

 scarcely a trace of similarity to that of the Himalayas* or the countries 

 west of the Indus or east of the Bay of Bengal. Wherever remains of 

 sedimentary beds are found throughout the peninsula, of any age from the 



* The only exception of any importance is the occurrence of Damuda rocks in 

 Sikkim and Assam. 



