50 MEDLICOTT, SHILLONG PLATEAU. 



a north-north-east strike, foliation is strongly marked ; while on the 

 Shillong ridg'ey with a general east -west strike, the dip is often flat, and 

 the foliation is scarcely traceable. Elsewhere, however, where the 

 contortion is extreme, the granular texture is preserved. 



Although such capriciousness of lithological characters is co mm on 

 over a large portion of the area, there is one very well marked tendency 

 observable when the whole extent of these rocks is considered. There 

 is on the whole a complete change of condition from north to south. 

 In the Shillong region, and even to near Surarim, crystalline meta- 

 morphism is only incipient or partial ; in the south, it is complete and 

 general. I have scarcely a doubt of the identity of the series through- 

 out : I have followed the rocks continuously down the valley under 

 Sm-arim into the valley of Nongpriong below Cherra, and so to the 

 southern boundary with the Silhet trap. In this region, gneiss shows 

 freely, associated with the quartzite, and, we may suppose, in great part 

 formed out of it. There are other concomitant features hereabouts : 

 dykes, large and small, of granite are frequent, cutting the strata in 

 various directions ; such phenomena, as far as my observations extend, 

 being altogether wanting in connection with the great granite masses 

 to the north. There is, at the same time, a decided prevalence of an 

 east- west strike in the compUcated contortions affecting the strata here. 



Should the feature I have described in the last paragraph, prove to 

 be generalalong the southern fringe of the table-land, as I opine it will, 

 it would involve an important modification of a statement made in ' the 

 second paragraph of this Section, regarding the independence of the 

 structural features of the Shillong series with reference to the con- 

 figuration of the table-land. That observation must remain true of the 

 main area of these rocks ; but it would be most interesting to find that 

 the area immediately south of the plateau, which has been shown to 

 have been more recently an area of very extensive trappean eruption, 

 and subsequently again an area of special disturbance, had been in very 

 ( 200 ) 



