43 GEOLOGICAL NOTES ON ASSAM. 



the western liills miglit geologically be considered a table-land^ though 



orographically they can scarcely be so regarded, denudation having 



operated so extensively that over the greater part of them there 



is not an acre of level ground to be seen. The tame, non-descript 



contour of this region may account for its having no single name 



throughout any considerable length. In the contiguous hills where 



the structure has led to the formation of high, peaked ridges, the names 



of Patkai in the north-east, and of Burrail in the south-west are 



applied throughout great distances to portions of the same range. As 



one must have a collective term for the western region, I will speak 



of it as the Shillong table-land, this being the name of the highest 



summit, and also the locality recently selected for the Head- Quarter 



station. 



The general structure of the Shillong table-land is what has been 



,. 1 1 ^ J. „ described in the Cossyah District, locally more or 

 General rock-features -^ > J 



of tlie table-land. jggg modified. Along the northern border granitic 



and gneissose metamorphic rocks occur continuously. The low hills 

 which, singly or in groups, occur so frequently over Central and Lower 

 Assam, especially south of the Bramahpootra, belong to the same series of 

 rocks. Eastwards they terminate in the large group of the Meekir HiUs ; 

 I know of no re-appearance of them beyond the Dimseeree. North of 

 Gowhatty and Goalparra they stretch away towards the Himalaya. 

 Westward the same rocks show obscurely on the right bank of the river 

 at Doobrie, striking into Cooch Behar. Thus a large part of the Assam 

 Valley seems to have been excavated in this gneiss. At many places 

 outliers of the horizontal rocks are found on the gneiss close to their north- 

 ern border ; but it would seem that this rock does not form the basis of 

 the table-land generally. The quartzite sandstones of Shillong and trap 

 have already figured largely in this position. There are also some very 

 considerable masses of schists and of slates, some showing little or no 

 signs of crystalline metamorphism. Regarding all these roch everything 

 remains to he made out, 

 ( 438 ) 



