Chap. IV.] nahun and sivalik groups. 131 



supposition of its being a great line of uniform contortion, and thus to be 

 the strongest argument I can make against the prima facie opinion, 

 that the Noon section is a continuous sequence of conformable strata. 

 We shall elsewhere find analogies to strengthen this argument. I 

 imagine the main boundary to be in kind quite like the inner Sivalik 

 boundary, as various as we know this to be, but in this latter case it is 

 more easy to detect where the strata are inverted, or where in their 

 normal order. 



In the eastern region the difficulty was the indication of any precise 



division in a series of very similar deposits, appa- 

 The western region. . . . 



rently conformable and transitional in one zone 



and irregularly but strongly unconformable in another. The same puz- 

 zle will occasionally occur in the western region ; but here the chief 

 difficulty is to indicate any defined break in a great series, the extreme 

 members of which are very dissimilar in many important respects. The 

 top rocks have a newer aspect, and the bottom ones a more ancient, than 

 in the sections to the east. In the Guggur on the east, and in the Ravee 

 on the west, there are seen two belts of rock which no one could hesitate 

 in separating ; yet in examining the intermediate area one would 

 include the greater portion of it with one or with the other of these 

 belts, according to the direction in which one proceeded. If examined 

 from the south-east most would be classed as a lower group, and from 

 the north-west the outer band seems to spread over well nigh all. When 

 the boundary comes to be traced, if indeed it ever can be,— if any conti- 

 nuous physical break in the newer Sub-Himalayan period exists in the 

 greater part of this western area, — the middle group will appear as strips 

 occupying the long narrow ridges which traverse the region more or less 

 continuously in a north-west, south-east direction. In several cases these 

 ridges disappear to the north-west, the lower rocks thus becoming 

 enveloped in the upper. 



