14 SUB-HIMALAYAN ROCKS OF N. W. INDIA. [CHAP. I. 



difference of general texture of the two rocks in contact is so slight as 

 to be quite compatible with the supposition that they belong to one and 

 the same conformable group, the top beds being simply let down by a 

 fault against the bottom ones ; but this impression is at once contradicted 

 by the fact that all the larger boulders and pebbles in the conglomerates 

 are of the Nahun sandstone. The identification is easy to any one who 

 is familiar with, the rocks to the north ; although, as a mass, the Nahun 

 rock disintegrates directly into sand, yet strings and lumps of it do 

 become tolerably hardened both by calcareous infiltration, and under 

 certain conditions of exposure. In the abstract published in the " Asiatic 

 Journal" for 1861, I separated these rocks on this ground alone. I have 

 since had the satisfaction of observing, within a mile of the Markunda 

 section, a distinct case of unconformable overlap of these same conglome- 

 rates on the Nahun beds * 



Conglomerates, more or less like those on the Markunda, form invari- 

 ably the top beds of the Sivalik group, and some- 

 times to an enormous thickness. They pass down 

 conformably, and with a gradual change, into an untold depth of sand- 

 stones and clays, the latter generally being very subordinate. In these 

 lower beds of this group I failed to discover any reliable primary 

 character by which to distinguish them from the beds of the Nahun 

 group. There is perhaps a shade of difference in the degree of indura- 

 tion of the two, but it is too slight and uncertain to be insisted on. 

 The upper conglomerates just mentioned lap over the denuded base of 

 the Nahun group. The distinctness thus established physically between 

 the two groups is borne out in a most important manner by fossil 

 evidence. This central region of our district; already so frequently 

 noticed as peculiar, is the classic ground of the Fauna Sivalensis, as at 

 present known to us. These giant fossils are found through some 



* The nests of lignite, which frequently occur in the massive sandstone beds of the 

 JSahun group, have more than once excited expectations regarding the discovery of coal. 



