TALCHEEK COAL FIELD. 77 



And although there is much difference in the thickness of corres- 



Difference of thickness ponding Strata, this is a matter of comparatively 

 less important. Why ? trifling importance, in considering beds which have 

 been so much denuded. It must, moreover, be borne in mind that the 

 thicknesses given by Mr. Hislop are only those of the beds as seen in 

 some particular places, while those here assigned to the Talcheer beds are 

 the estimated gross thichness of each series in the area. 



Of the thickness of his second group, Mr. Hislop professes his ignorance, 

 mentioning 15 feet only as that of the argillaceous shale immediately 

 underlying the upper sandstone.* 



The limestone is indeed wanting in Orissa ; but it seems very doubtful, 

 whether it is even approximately of the same age as the overlying 

 beds, as it is clearly a metamorphosed formation, and, according to 

 Mr. Hislop, altered by the granite of the plutonic formation on which it 

 rests.-f- It is certain that the limestone is of a later date than the 

 ordinary metamorphic rocks of the district, since it rests on their denuded 

 surface, but it may well have become altered by some of the subsequent 

 outbursts of greenstone, pegmatite, &c., and still be much older than the 

 sandstones and shales which are unaltered. It is indeed stated by Mr. 

 Hislop that the sandstone of Sitabaldi Hill, near Nagpitt, is meta- 

 morphosed to a considerable extent, though he does not mention any 

 cause, which in this case is probably the trap of the hill, j 



We thus appear to have strong reasons for believing that these same 

 beds, described by Mr. Hislop, formerly extended with but sHght alteration 



* Mr. Hislop, in his later paper on the XJmret coal, estimates the beds (of the middle and 

 lower groups) at 300 feet and 80 feet respectively, and states that the latter are much sunken 

 to the East. (Quarterlij Journal Geological Society, Vol.- XL p. 560.) 



+ May this be a granitoid gneiss ? 



J If, as seems highly probable, the relations of the metamorphic rocks of Nagpur with the 

 shales, sandstones, &o. of the district be the same as in Orissa, probably Mr. Hislop errs in 

 attributing the disturbances observed to the plutonic intrusions in the district (excluding 

 trap.) If, as in Orissa, all these intrusions of pegmatite and greenstone, &c. were prior to 

 the deposition of the sandstones and shales, the distm'banoes must of coui'se, as in Orissa, be 

 due to subsequent upheaval, faulting and denudation. 



