GENERAL CONSIDERATIONS. 



49 



Mr. Medllcott between the Sirguja and the Sohag-piir coal-fields. A 

 serious difficulty is thus opposed to the acceptance of the example which 

 I brought forward ; for the conditions existing there would only account 

 for a fringing deposit. 



The conjecture that was hazarded in the report on the Talchir field, 

 that grouud-ice might be the chief agent in the transport of boulders, 

 receives no confirmation in the existence of scratchings on the stones, 

 or angularity in the shape of the debris. The absence of this testimony 

 is, however, of no great moment, considering the mode of formation of 

 ground-ice and the manner in which it transports material. The most 

 serious difficulty, and the one which must be recognized, is that of 

 climatal conditions. 



Boulder beds occur high up in the series, and in the Bokaro coal- 

 field, there is an instance in the Biida (Boodah) river of a boulder bed 

 in direct contact and conformable with a typical Barakar sandstone. 

 Here, the contrast in climatal conditions is so forcibly brought before 

 us that one ought to accept with caution the accuracy of the ground- 

 ice-theory, until other explanations have been disproved which are 

 prima facie more in accord with the conclusions deducible from the 

 stratigraphical relations of the two series — Talchir and Damuda — and 

 the universally admitted conditions under which coal has been formed. 



If we duly weigh the bearing which the evidence of unconformity 

 that occurs between the Talchirs and Damuda has upon the variation in 

 climatal conditions existing during .the deposition of the boulder bed, 

 we find that the unconformity is one of mere overlap, and does not denote 

 any great break in time of the process of deposition, such as is implied 

 by the upheaval and denudation of one set of strata previous to the 

 formation of another, but rather a change in the degree of intensity 

 with which existing formative forces acted. 



The relation between the Talchirs and Barakars is too intimate, as 

 shown by the occurrence of similar plant remains and by the strati- 

 g ( 333 ) 



