10 SUB-HIMALAYAN KOCKS OF N. W. INDIA. [CHAP. I. 



has been examined since then, as well as old ground revisited, the views I 

 then expressed have undergone but slight modifications. From end to 

 end of our map we find two series of rocks strongly contrasting in com- 

 position. It is only provisionally that I speak, collectively, of the inner 

 and older of these series. It comprises limestones, shales, sandstones, 

 slates, grits, quartzites, schists, and gneiss, — an assemblage offering ample 

 room for classification ; but I have as yet only conjectures to offer as to 

 their mutual relations. These conjectures will be placed together in a 

 separate chapter. I will frequently refer to these rocks throughout the 

 following memoir under the indefinite names of Inner and Older rocks. 

 The outer rocks, on the contrary, form a well marked geological series or 

 system, although composed of several distinct groups and sub-groups. In 

 honor of the most distinguished of these groups, I might designate the 

 whole as the Sivalik series ; the details of its characters would be found 

 to justify this name, but, on the whole, and as not involving an idea of 

 geological age, I think the more general term of Sub-Himalayan series 

 will be more suitable. 



With one exception, the newer, and the older rocks are separated 



„ . , „. , throughout by a well marked boundary, along which 



Base of Sub-Himalayan & j •/ ° 



series, they are in vertical contact. The contrast is striking 



to the least skilled geologist, and there can seldom be any hesitation in 

 iudgino- from the relative conditions of the two rocks which is the older. 

 Such a junction, however, would be a most unsatisfactory horizon, or 

 rather no horizon at all ; it would leave the question of the original 

 relations of the two series quite uncertain. The exception to which I 

 allude clears up this question in the most satisfactory manner. Over a 

 considerable area about the middle of our map, nearly occupying the 

 whole lenath between the Sutlej and Jumna, there is to the north and 

 east of this marked boundary line an outlier of the Sub-Himalayan 

 series. We here find the base of the series, and its original junction 

 with the underlying rocks,— a true geological horizon. The bottom beds 



