1S70] TJie Geological Survey of India. 461 



at a classification or knowledge of the order of superposition of 

 the rocks in India ; and when the vast area embraced by each sheet 

 is taken into consideration, it is not surprising that few have been 

 completed. 



A glance at the map best shows the amount of field-work that 

 has been done, and considering the many difficulties and dangers 

 that have had to be encountered — not forgetting the disturbed state 

 of the country during the Indian mutiny in 1857 — we must con- 

 gratulate the Survey on the great progress it has made. 



Besides the preparation and publication of the geological maps, 

 the Survey now maintains three periodicals of letter-press. 



The first part of the ' Memoirs ' appeared in 1856, and since 

 then six volumes have been completed, containing thirty-two geolo- 

 gical reports (over 2200 pp. of letter-press), and the first part of 

 vol. vii. has recently been published. All are well illustrated with 

 maps and sections. 



Particular attention has been given to the coal-bearing deposits. 

 The ' Memoirs ' contain reports on the Coal-fields of Talchir, Bani- 

 gunj, Jherria, Bokaro, Eamgurh, &c. 



The coal-fields of Bokaro and Eamgurh belong to the ordinary, 

 or Dainuda series. 



In the Jherria coal-field, the two series, Talchir and Damuda, are 

 developed. 



The lower, or Talchir, contains no coal. 



The Damuda series contains many seams, very irregular, and 

 varying in thickness from a few inches to 20 feet and more. Nume- 

 rous coal-seams are much injured by trap-dykes, which have ramified 

 through them, and which have rendered the coal useless. There 

 is also a general tendency to ignition in all the seams, owing, it is 

 thought, to the presence of iron pyrites, which gives rise to spon- 

 taneous combustion. Metamorphism is produced in the shales in 

 proximity, giving to them the character of well-burnt bricks. 



Dr. Oldham calculates that there is an available quantity of coal 

 in this Jherria field of about 465,000,000 cubic yards, or, roughly, 

 tons of coal. 



In Sinde there is a lignitic coal of Lower Tertiary age, but not 

 worth working. In one of his earlier reports Dr. Oldham noticed 

 the existence of Tertiary coal by the river Irrawaddy, near Prome. 



Coal of excellent quality has been found in Assam, which lies 

 near the river Brahmapootra, convenient for transport by water. 



Considerable doubt attached to the age of the coal-fields of 

 Damuda, Talchir, and Nagpur. The reported discovery in them 

 of certain plants was thought to place them in the Triassic or 

 Oolitic period. But it has since been ascertained that these re- 

 mains occur in shales above and distinct from the Coal-measures. 



Comparisons have been made of late between the several series 



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