13G Mr. CoLEGRooRE OH the North-cast of Bengal. 



putra river, the rocks exhibit granite, quartz rock, and a sandstone or conglo- 

 merate of water-worn quartz pebbles with argillaceous cement. 



Proceeding inland from the river, in an easterly direction, to Robagiri*, 

 a village of tiieGaros, distant twenty-five miles, the country consists of hills of 

 sandstone interspersed with blocks, and occasionally larger masses of gneiss, 

 and of a rock composed of felspar and quartz. The beds of the rivulet, north 

 of the village, exhibit white clay ; and the hills in that direction are composed 

 of the same clay alternating with white sandstone, in many places containing 

 rounded quartz pebbles, and angular pieces of felspar. 



Further north, at a distance of three or four miles, is a mountain more than 

 four thousand feet above the level of the village. Where the rock shows 

 itself, it appears to consist of quartz and felspar without mica. 



In the bed of the river, at the foot of the village of Robagiri, a stratum of 

 shell limestone is seen above the clay, and is surmounted by another argilla- 

 ceous bed, which contains shells of a similar character, but in smaller number. 

 In some places the limestone seems to contain bones: but no perfect specimen 

 has been extracted. 



In general the Garo hills may be described as of two orders. The first, 

 rising to the height of two or three thousand feet, and in some places more, 

 are composed of granite with veins of unmixed quartz beneath, and of pure 

 white felspar towards the summits. 



The hills of the second order are seldom above 150 or 200 feet in height. 

 They appear to have been formed, from the first, by the operation of water : 

 the strata being nearly horizontal, and their substance composed of clay, 

 sand, and small stones ; red in the neighbourhood of red granite, and white 

 where felspar of this colour prevails. 



The granitic character of the upper Garo hills is continued into Asham : 

 and the semicircular bend which the Brahm-putra river takes on its entrance 

 into Bengal, is round a granitic promontory of moderate elevation, at the foot 

 of which lies an undulated alluvial country. Among specimens received from 

 thence, ferruginous sandstone and also greenstone occur. 



Further east, towards Silhet, at a place named Laour, shell limestone abounds. 

 It consists in a great measure of nummulites. Specimens, which were re- 

 ceived thence, with the information that the lime, which Silhet supplies to all 

 Bengal, is procured from inexhaustible beds of that limestone at the Laour 

 hills, are in the Society's collection. The fact merits notice, as it indicates a 

 later formation than transition limestone, for nummulites have not been found 

 in that situation. 



* Some furtlicr details respecting tlie vicinity of this place, from a subsequent communication 

 by Mr. Scott, will be found among the notices in the present volume, — Article XIII. 6. 



