Chap. IV.] nahun and sivalik groups. 119 



quality of the boulder deposits are very suggestive as regards the physical 

 conditions during the Sivalik period ; at least they leave no doubt upon 

 some important points. The greater accumulation of boulder deposits in 

 the immediate regions of the great rivers is very noticeable. This fact 

 happens to be most conspicuously seen in the case of the Jumna ; the 

 thickness of sandstone-conglomerate in the cliffs of Amsot is remarkable. 

 Throughout the Sivalik hills proper the general description of the mate- 

 rials of these deposits is the same ; with a greater or less amount of the 

 debris of limestones and of other rocks that may be derived from the 

 Masuri ridge, there is a large admixture of the same boulders as are now 

 only to be seen in the beds of the great mountain torrents, a schistose 

 quartzite being the prevailing variety. The rapid suppression of the 

 Sivalik rocks to the east of the Ganges prevents our carrying the com- 

 parison in that direction, but west of the Jumna there is most complete 

 evidence of the changes. In the hills south of Kyarda, we still see the 

 same description of debris as on the east of the Jumna : this is not 

 merely the case in the northern portion of the range, it also holds good 

 at Simulbari in the southern ridge, formed by conglomerates evidently 

 in continuation with, and the representatives of those just south of Kolur. 

 At this latter place, however, the conglomerates are as prominently made 

 up of hard purple sandstone identifiable with the rocks of the Subathu 

 group, such as now abound in the bed of the Batta. It is only in the 

 small pebble-conglomerates at the base of the sub-group, that the 

 detritus of the older rocks is still traceable ; and in this position in the 

 section it is constant throughout the whole district. Within a very few 

 miles to the west another change is effected. It has already been brought 

 to notice that all the larger debris in the conglomerates of the Markunda 

 section is of Nahun rocks. The fact, that in the form of debris this 

 distinction is clearly marked, is strongly confirmative of the separation 

 that has been made between the Subathu and Nahun groups, and of the 

 very decided separation from both of the strata now containing this debris. 



