48 GEOLOGICAL NOTES ON ASSAM. 



impossible from the very scanty data before us to conjecture how far the 



moving causes of the great rock disturbance I have described may have 



been external to, or independent of, the mass affected, or how far they 



may have resided in that mass. The two points I would insist upon are, 



the marked manner in which local conditions have influenced such vast 



rock movements, and the related fact of a great and sudden change of 



direction in one and the same great instance of disturbance. 



I have said that the Burrail seems to be an ascending section from 



, . ,, north to south. The outermost strata on this 

 Same rocks m the 



plains of Cachar. latter side are probably not represented at all 



beyond the ridge ; they seemed to be the same as those forming the 

 nucleus of the little hills and ridges, locally called feelaJis, about Cachar. 

 I saw some fresh cuttings in these rocks on the Sylhet and Cachar road 

 near Kategm'rah. There is much irregularity in composition and ar- 

 rangement, both original and induced. Clear sandstones are associated 

 in the most intricate manner, by oblique interlamination, with fine shaly 

 clays, and all have undergone much irregular crushing. In the sand- 

 stones I noticed large blocks of silicified palm-wood, and well preserved 

 impressions of leaves ; ■^" the clays also contain confused fossils. All these 

 strata are probably of middle or upper tertiary age. The rock on 

 which the little fort of Kategurrah is built is rather a puzzling one. On 

 the river front it presents a most regular dome shape ; the only di\d- 

 sional plains being those of rough uoncentric exfoliations ; there are 

 also minor spheroids within the mass, generally stained dark brown by 

 iron ; the texture and composition of the mass is equally undecided as to 

 a mechanical origin ; I considered for some time whether the whole 

 might not be a deeply decomposed boss of fine granitic rock. It is most 

 probably an extraordinary accumulation of the sandstone, which it 

 resembles much in textm'e. 



* These are all of dicotyledonous trees. — T,0. 



( 434 ) 



