30 
On the Sub- Himalayan rocks. 
[No. 1, 
The continuity of this fault renders it probable that its throw is 
very considerable. To attain anything like an exact estimate of 
this, the position of the Nahun beds in the general series must be 
ascertained. This is by no means an easy question. And though 
not prepared to settle the point definitely, it may be useful to show 
how the matter stands. 
Capt. Cautley referred the Nahun rooks to the lowest member of 
his threefold division of the Siwaliks (see above). Now large mamma- 
lian remains are found in the earthy sand and boulder beds imme- 
diately to the south of the fault, thus the top and the bottom beds 
of the entire series so far as we know them, are here brought into 
contact. But, further, the boulders in this outer rock, at the junc- 
tion, are boulders of the lignite sandstone of Nahun hill ; there is no 
other rock in section to the north that could have yielded them. And 
this fact would seem to involve either a want of strict correspondence 
between the Nahun hill beds, and any others in the section to south 
of them, or else, a total break of conformable sequence in that section. 
A much more careful examination of fossils and of the strata, than a 
preliminary survey would warrant, will be required to decide this. 
This raises a question as to the successive deposition, and upheaval 
of great banks of these Siwalik strata, which again recurs in the 
west. It has long been noticed, that there was a great expansion of 
the Siwalik area in the west, commencing just beyond Kalka and Kas- 
sowli. It is occasioned by a curve in the great boundary fault, 
which here alters its direction to about 15° W. of N. ; while the 
outer line of the Siwalik hills preserves nearly its former direction. In 
Mr. Greenougli’s map the sharpness of change in the boundary about 
Belaspur is exaggerated both by inaccuracies in position of localities 
and because he includes the Sabathoo, or upper Nummulitic group, 
the inner or northern boundary of which is much more irregular than 
the main fault which separates this group from the Siwalik series. 
Now the Siwalik rocks occupy this increased area, not by the 
extension of the strata already noticed, but by the successive intro- 
duction, by faults, of other bands of rock not strictly identifiable 
with the outer Siwaliks. Even at the Sutlej there are two such 
bands between the Nahun ridge and the main fault, as seen near 
Belaspur. 
