GENERAL CONSIDERATIONS. 121 



Nahans, we find that what is true as regards the original limitation of 

 the Siwalik conglomerate is true also of that of the sand-rock, though 

 in a less degree. The rivers then were not so exactly placed as they 

 are now, but still their general disposition must have been very much 

 the same. 



The main boundary between the Nahans and the older rocks to 

 the north must also be looked upon, though still 



The main boundary 



also a limit of deposi- less absolutely, as a limit of deposition. The 

 winding nature of this fault, as it follows the 

 main curves of the Himalayan range, is the chief argument that we 

 have to rely on here. In the case of many of the larger rivers we see 

 an inbaying of the boundary towards the hills, corresponding to what 

 would be a present contour line. Take a look at the geological map 

 accompanying Mr. Medlicott's memoir, and see how at the north- 

 west end of the region there is a sharp inbaying up the Ravi ; then 

 a steady line following the trend of the Dhaoladhar ridge ; then a 

 great inbaying, on a large scale, towards the debouchure of the Beas 

 R. from the higher hills ; and then a more or less steady line 

 until the Jumna is neared, when another inbaying of the bound- 

 ary takes place, followed by smaller bends between that point and 

 the Ganges. That the same is true in the region covered by my 

 own memoir is similarly apparent to the eye. Can a boundary 

 such as this be anything but an approximate boundary of deposition ? 

 Can we for a moment suppose the Nahan zone a fragmentary 

 relic of a great fold of the rocks which carried them once far 

 above the Outer Himalayan mountain mass? Decidedly not; this 

 moulding of the Nahans in and out among the irregularities of 

 the older mountain mass is the natural result of deposition round 

 a winding mountain-foot. The Himalaya must have stood roughly 

 blocked out as they now stand when the Nahan sandstones were being 

 deposited. We have already seen that the minerals of the sand- 

 stones tell the same tale; whilst the embedded mammalian remains 

 point also to a limited deposit, with high land not very distant, from 

 which the material was derived in which their remains were speedily and 



( 179 ) 



