Chap. VI.] . general structure of hills. 169 



The prima facie interpretation of all this superficial symmetry would 



T , , f , be that it had been produced by one great act of 



features of disturbance U p neava ] subsequent to the formation of all these 



being due to one great r u 



act of upheaval, after roc k s having its axes of maximum effect, — one 



the formation of ail the ° 



rocks, tenable ? a ^ or nor fa f the line of peaks, and the other 



well to the west of the Ganges. The difficulty, as it now presents itself, 



is to reconcile so much symmetry with the great 

 Objection to it. 



difference, both in time and in mode of produc- 

 tion, which can be almost demonstrably established. The problem is 

 brought within small compass in the section of the Dhaoladhar (p. 63). 

 The structural features of that section would accord well with the sup- 

 position that the granitoid mass forming the ridge had been introduced 

 by faulted intrusion subsequent to the formation of the Sub-Hima- 

 layan strata. It has, however, been shown that when these rocks 

 were formed the ridge existed pretty much as it does now, and that 

 the boundary between them and the older rocks is to a great extent 

 an original one, their relative positions having never much altered. 

 In the case of the upper Sub-Himalayan group, which is often much 

 more disturbed 'than it is represented in this particular section, it 

 was shown to be contemporary with the existing river gorges of the 

 mountains. It is in the region of the Lower Himalaya that this dis- 

 tinction can be best studied. We there find a zone of maximum contortion 

 along the line of contact of the Sub-Himalayan with the Himalayan rocks, 

 and separated from the great range of the Eastern Himalaya by a wide 

 area of comparatively little contortion and of somewhat different character. 

 These remarks seem to me to lead to the conclusion that the features 

 Features of disturb- °^ disturbance in these youngest rocks have no 

 "obabi; nT&ecttd direct connection with the formation of the 

 Sn?dnt rm buJ° n indi^ mountains. But connection there most decidedly 

 ions o t eir su si ence. - g j j^^g ^e disturbance of these rocks to be 



entirely a reflex effect. As the composition of the Sivalik strata and 



x 



