CHAPTER X. 



ALLUVIUM. 



The alluvium in the neighbourhood of the Rajmehal hills is so in- 

 separably connected with that of the Gangetic Valley generally, thatthe 

 discussion of its relations would involve the description of a much larger 

 area than that included in the accompanying map. 



It may be sufficient to state here, that two general sub-divisions of 

 the alluvium are recognised, viz,, old and new. 



The old has been by some authorities considered to be of marine 

 origin, but conclusive evidence in support of this view is still a desidera- 

 tum. "Within our area the clay on top of Patharghata Hill, a section of 

 which has been given on a previous page, was considered to afford 

 evidence of a once continuous bed of this old alluvium having stretched 

 across the country at a level at least 100 feet above the present flood 

 surface of the Ganges. The true character of this superficial accumu- 

 lation on the hill, consisting of clay with debris of rocks, kunkur, and 

 rubbish of the human period, is far too uncertain to be of much value in 

 a question of this importance. 



To the older alluvium period, the laterite, though it has been above 

 described separately, may at least in part belong. The kunkur-bearing 

 clays are probably also chiefly of that age. 



There has been no attempt in the accompanying map to distinguish 

 the two forms, although demarcation of the respective limits was carried 

 out to some extent in the field, but not completed for the whole area. 



For further information on this subject, the reader is referred to 

 Mr. Theobald's paper in the Records of the Geological Survey, Vol. Ill, 

 entitled " On the alluvial deposits of the Irawadi, more particularly as 

 contrasted with those of the Ganges." 



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