170 KHASI HILtS. 



aspect of the surface. And, further, the action of these forces appears to 

 have been determined, as to the direction of its maximum effect, by a 

 series of lines of jointing and fracture, and occasionally of dislocation or 

 faulting, resulting from the earlier intrusion of the volcanic rocks. 



The very gradual and continuous slope of the plains at the foot of the 

 hills, will show that long subsequently to the period of their elevation, 

 a sea had washed their base, and formed the widely-extended flats, from 

 which their steep escarpments rise. 



Viewed in connexion with the geology of India, in a wider and 

 more general way, one of the first points which arrests attention is 

 the remarkable coincidence in the general direction of the main lines of 

 disturbance in these hills (East and West), and of those which have 

 affected the coal-fields, or " Damoodah" and " Mahadeva" groups of Ben- 

 gal and of Central India. Whether there be any synchronism, as 

 would appear probable, can only be determined by more widely extend- 

 ed examination. At the same time I would refer to the bearing on 

 this question of the supposition I have already thrown out (a), that 

 it may not be improbable that the great lines of disturbance 

 traceable in the Nerbudda valley, may be continued up the Assam 

 valley. But even if these disturbances be synchronous to a certain 

 degree, it will not at all follow that the whole extent of the disturbance 

 or fault was produced at the same time. Disturbances may have been 

 frequently repeated along the same or parallel lines of weakness. 



Aarain, the circumstances under which the nummulitic rocks occur 

 in the Khasi hills are curiously similar to that under which they are 

 found elsewhete in India. They are generally indicative of a moderate 

 depth of water (see page 169), and they are here also only found in the 

 proximity of the mountain range. It is remarkable that these facts 

 should be so constant, and that these nummulitic rocks should not 

 occur anywhere in the broad plains of the Indian peninsula. This 

 (a) Journal of the Asiatic Society of Bengal, 1856. p. 250, 



