1S75.] part of the Dqfla Sills, Assam. 37 



of gneiss, clay shales, and dark-coloured sandstones belonging to a diffe- 

 rent series of rocks, with a few pebbles from Tertiary sandstones, shewing 

 that the river must cut through the whole series of stratified rocks up to 

 the metamorphics. This I afterwards found to be the fact. I found here 

 several pieces of silicified wood (a large grass) 8 inches in diameter. The 

 first exposed section, seen about four miles further up the Sibjuli, presented 

 the Tertiary sandstones with a high dip, 75° SE by S. : these are here very 

 dark and hard, thick-bedded, with a slight violet tint. They contain no 

 pebbles, and are of a different character from the outer or Dihirhi group 

 of beds. At the low pass over into the Harjuli they are thin-bedded, softer, 

 and vertical. Passing on northward, on the SE. spur from Tanir Peak, 

 the sandstones are horizontal, and evidently roll over at the Peak to 35° 

 NW., which is the dip all along the crest of this second ridge. Crossing it 

 and proceeding down the spur to the Dikrang, at the few places where the 

 sandstone is uncovered, the dip has become high to the North-west-ward. 



But it was on the Dikrang itself that the most interesting section 

 was obtained. On following up the first and eastern stream on the right 

 bank of that river near Camp No. 6, below the village of Shikhi (Phekfis), 

 the first trace of an older series of rocks was found, about a quarter of 

 a mile up the bed, where a dark, hard, heavy sandstone occurs, vertical 

 with a NE. — SW. strike. The soft Tertiary sandstones immediately suc- 

 ceed, having a local dip E. by S. 75° : they are much crushed, very thick 

 bedded and micaceous, with scattered small pebbles, and they appear the 

 equivalents of the sandstones of Dihirhi. Proceeding up the bed of the 

 next stream (the largest, which I shall, for the sake of distinction, call the 

 Tanir juli, became it drains the northern face of the Tanir ridge), we first 

 come upon the Tertiary sandstones nearly perpendicular, strike SW. — NE. ; 

 a very few yards further on are clay shales, very dark and carbonaceous, 

 dip 70° high, NW. Some 50 yards further up the stream, the dip was 

 reversed to 75° ESE., with considerable crushing, and here occurred a 

 thick seam of black carbonaceous shale 5 to 6 feet thick, interstratified with 

 dark close-grained sandstones ; this can be traced along the strike NNE. — 

 SSW. for 200 yards, as it crosses the bed of the stream three times. It 

 is rather a crushed splintery coal than a shale, and no doubt would 

 prove better below the surface. Where now exposed it is either in the water 

 or just out of it, in fact, to see it at all one has to wade up the bed of the 

 stream, the jungle on the banks being too thick to move about in. 



It was most interesting to come on these rocks in this position, as they 



are no doubt the representatives of the Damuda Series lately examined and 



worked out along the base of the Darjeeling and Western Bhutan mountains 



by Mr. F. B. Mallet * and first noticed by Dr. J. D. Hooker in 1849, near 



* Memoirs of the Geological Survey of India, Vol. XI, Pt. I. 



