INTEODUCTION. 



the same metamorpliie series that occurs in it. The Bramahputra 

 is slowly enveloping these hills in its alluvium. 



The length of the Shillong plateau, from Golaghat on the Dunsiri, 

 to Singm^ri on the Bramahputra, is about 250 miles. The width would 

 average about 25 mUes. The general level of the plateau S-anges between 

 4,000 and 6,000 feet. 



The only part of the Shillong plateau that has been examined in 

 any detail is a narrow strip about its centre, in the region inhabited by 

 the Khasias, from Cherra Ptinji on the south to beyond Shillong on 

 the north. It was here that Mr. Oldham inade his observations in 1851 

 and 1852 ; it was here that I made an eight-day excursion in 1865 ; 

 and it is here that I have again had an opportunity of more minute 

 examination. It seems probable that all the rocks of the plateau are 

 represented on this middle section. 



I would briefly recall the general geological features : at the two 

 extremities, Singmari and Golaghat, cretaceous strata rest undisturbed 

 upon metamorphic rocks ; and throughout the intermediate length, on 

 the southern half of the plateau, the same condition obtains, sandstones 

 of the cretaceous period lap up horizontally, more or less continuously 

 or in outliers, upon the metamorphic rocks; which latter show an 

 unbroken range along the northern face towards Assam. At many 

 points large patches of nummulitic strata cap those of the cretaceous 

 period; and on the south-east portion of the table-land, where the 

 area of the sedimentary rocks is broadest, beds younger than the 

 nummulitic, and possibly of middle tertiary age, are largely developed, 

 maintaining the horizontahty characteristic of the table-land area. 

 It is, indeed, only on the strength of the stratigraphical conditions 

 that this portion of the area can be brought under the designation 

 of table-land j the soft massive sandstones of the younger forma- 

 tions present such general homogeneity of texture that they have 

 been deeply eroded, producing a surface of steep undulations, or 



( 153 ) 



