Mr. CoLEBROoRE ow the North-east of Bengal. 133 



western extremity of the range marked on maps as opposite to Jogigopa. 

 The rock% in the only place where it is exposed^ has been much affected by the 

 weather. It appears to consist of gneiss. The masses (or strata) run from 

 north-east to south-west, dipping to the south-east at an angle of about forty- 

 five degrees. They are crossed by transverse cracks from south-east to north- 

 west, and veins of quartz in some places follow that direction. 



AtGwalpara, some miles eastofPaglanat'h, granite is found. Amongspecimens 

 received from thence, is one which consists of felspar, hornblende and mica. 



The Brahm-putra, shortly after its entrance on Bengal, receives from the 

 Bhotan mountains the tributary stream of the Gadadhar, which has its source 

 near Tesisudon. Near their confluence is the hill of Dhabni : it rises not more 

 than thirty or forty feet above the level of the adjacent plain ; and the lower 

 portion of the acclivity has been covered by alluvial soil. But on the south- 

 east and north-east sides of it, where it has been cut by the waters of the 

 Gadadhar and Brahm-putra rivers, good sections are observed. The banks 

 are there composed of crumbling gneiss and large-grained granite; in some 

 places intermixed ; in others distinct and alternating. The position of the 

 masses (or strata) varies from an almost vertical one to an angle of forty-five 

 degrees; and where they incline, it seems to be to the south-west; that is, 

 they dip to the north-east. The direction is nearly south-east and north-west. 

 On the north corner, the hill terminates in the river in large blocks of gneiss, 

 which are nearly perpendicular where they join the body of the hill. Blocks 

 of green stone, containing metallic specks, apparently of magnetic iron ore, 

 are found in various parts of the bank. 



A little lower down, the Brahm-putra receives the Kelanki river from the 

 Garo hills. It issues from those hills about lat. 25° 40', and long. 1° 40' east 

 of Calcutta. At their confluence, and on the left side of the river, a precipi- 

 tous bank occurs, exhibiting graphic granite and gneii-s. This rock consti- 

 tutes the lower part of the hill. In the bed of the river are found blocks of 

 stone of different sorts ; as granite, gneiss, various compounds of quartz and 

 felspar, and quartz united with felspar and hornblende. 



On the left bank of the Brahm-putra are the Caribari hills or cliffs. Prom 

 the confluence of the Calii, where it comes in contact with these hills, to 

 Mahendraganj, where they recede eastward, the appearance is nearly uniform. 

 The cliffs in general consist, at the bottom, of slate-clay disposed horizontally. 

 Above this, and in some places below it, there is a stratum of yellow (or, more 

 properly, green) sand, which is often found indurated at the bottom, and ac- 

 companied by ferruginous concretions. Over this there is in many places a 

 stratum of slate-clay ; and above that the bank consists of sand, white or rod. 



