1870.] The Geological Survey of India. 463 



mapped, any estimates of the Coal-resources and production of British 

 India must be defective. 



Besides the coal-reports, the * Memoirs ' contain papers on the 

 gold-bearing and other economic deposits, also many describing 

 the geology generally and physical geography of particular areas. 

 Some few treat of palaeontology. 



One very important paper describes the Yindhyan ^ series, as 

 exhibited in the North-Western and Central Provinces of India. 

 The district described included the greater part of Bundelkund. The 

 Yindhyan series is divided into an upper and a lower division, the 

 former gives rise to great table -lands, the latter furnishes more 

 diversified scenery. The area affords many striking instances of 

 the power and effects of subaerial denudation on a grand scale. As 

 yet the Yindhyan rocks have yielded no fossils ; they appear to be 

 older than the Talchir, and may possibly turn out to belong to a 

 period about the age of the Devonian. Pathologically they consist 

 of alternations of limestones, shales, sandstones, and conglomerates, 

 often distinguished by local names, as for instance the " Bijigurh 

 shales." Some of the beds furnish good building stone. 



In order to gain a more rapid publication of many isolated facts 

 noticed during the progress of the Geological Survey, and which 

 were scarcely adapted to the l Memoirs,' a new publication called the 

 'Kecords' was started in 1868. The series contains notices of the 

 current work of the Survey, lists of contributions to the Museum 

 and Library, &c, and it is intended also to publish analyses of such 

 books published elsewhere as bear upon Indian geology, and gene- 

 rally to notice all facts which come to light illustrative of the 

 geology of Hindostan. The third volume is now in course of 

 publication . 



Among the numerous published Keports the following appear 

 most worthy of special notice. 



The Surat Collectorate, in the Bombay Presidency, although a 

 comparatively flat country, possesses many features of geological 

 interest. Traps, ranging from basalt to a soft shaly-looking amyg- 

 daloid, are met with, and resting unconformably upon these is the 

 great Numnrulitic series. This consists of sandstones, conglome- 

 rates, and limestones, with nummulites, molluscs, fossil-wood, and 

 fragments of bone. Alluvium covers a large extent of the district, 

 and the cotton (or black) soil covers it over many large tracts of 

 the country. This soil seems to be the residuum left by the decom- 

 position of an alluvium largely composed of volcanic (trappean) 

 debris. It usually occurs in districts in which trap-rocks abound, 

 as for example in the Poorna valley, West Berar. 



The Poorna alluvium is of considerable depth, in places about 

 150 feet. Much of it produces efflorescences of salts, chiefly of 

 soda ; and in many places the wells sunk in it are brackish or salt. 



