46 PEOCEEDnTGS OP THE GEOLOGICAL SOCIETY. 



marked correspondence between the distribution of the accumulations 

 of conglomerate and the position of the actual river-gorges of the 

 mountains ; even in front of some of the lesser streams, with very 

 contracted drainage-basins, this limitation is well marked. Yet 

 these conglomerate masses are often as thick and at as high angles 

 as those on the Eigi and the Speer. 



It was along the junction of the Sivaliks with the IsTahun group 

 that I found the sanction for the explanation I was disposed to apply- 

 to the main junction of the Subhimalaya with the older rocks of 

 the high mountains. That line of contact of the two younger groups 

 is mostly concealed along the inner slopes of those longitudinal 

 valleys known as " duns." For about twenty miles midway in the 

 space between the Jumna and the Sutlej the Sivalik hills are con- 

 fluent with those of the J^ahun band ; and the junction of the groups 

 can here be followed vrithout a check. The character of it is most 

 constant, and uniformly of the type already noticed. The con- 

 glomerates dip at various angles, high and low, against the bottom 

 beds of the Kahun band ; they seem to go under, or to be buried in, 

 the older rocks, the plane of contact actually underlying to the 

 north. Here then, again, we have a jprimct facie case of reverse 

 faulting, of lower rocks slipping up over younger ones. A doubt of 

 this is first raised by the fact that the conglomerates contain much 

 debris of the Nahun rocks. There is, however, an actual section 

 which seems to render* impossible the supposition of any faulting 

 whatever : on the same boundary, and within half a mile of a grand 

 section of abnormal superposition, we find the same conglomerate 

 beds dovetailed into a serrated steep denuded surface of the same 

 Nahun beds ; and, further on, the younger beds broadly overlap the 

 older. The process of formation revealed by these sections is, that 

 the Upper Sivaliks were deposited against a steep denuded edge of 

 the older group, the present inverted plane of contact being due to 

 subsequent lateral pressure, which has not otherwise displaced the 

 original boundary by any vertical relative motion of the masses in 

 contact. 



In spite of the great un conform ability I have just noticed along 

 the inner boundary of the Nahun and Sivalik groups, it would seem, 

 according to the identification made by Sir Proby Cautley, as already 

 noticed, that these same groups at the base of the Sivalik section, 

 some miles to the south, are in apparently unbroken sequence, both 

 being now much disturbed. Such a fact would be most convincing 

 proof of the exceeding gentleness and partiality of the process of 

 disturbance. Should any doubt hang over this point of e\idence 

 owing to the unconfirmed and originally incompleted palseonto- 

 logical observations upon which it rests, there is sufiicient indepen- 

 dent proof of the same inference as to the nature of the disturbing- 

 process, in the permanence of Prsesivalik stream-courses. If this 

 we 'e only observed in the case of the great gorges of the higher 

 ir ountains one would scarcely be surprised. These tortuous gorges 

 ate manifestly the work of rivers ; but one has to encroach deeply 

 upon geological time for the accomplishment of such results. In 



