PART 2.] 
Medlicott: Sal-Himalayan Series in Jamu. 
51 
whole area as Siwalik, giving due notice of this on the map itself and in the descriptive 
test. Thus already in the Kangra district the Nahan-Siwalik boundary was extremely 
difficult to fix. 
The other great boundary-feature of the Simla region, that between the Nahan and 
Sirmur groups, also undergoes much change immediately west of the Satlej ; and in a similar 
manner to that described for the Nahan zone ; the whole Sirmur group becomes lowered along 
the strike to the north-west, so that the Subathu zone is altogether suppressed. On this 
account, and because this structure would probably bring in higher beds, the north-western 
extension of the Sirmur band was coloured as Nahan in my map of 1862. It is for this 
zone the beginning of the compromise that must be adopted to reconcile the different distri¬ 
bution of the strata in the separate sections of the mountain region. The actual boundary 
of this innermost tertiary zone is still as clear as ever, because there is a corresponding 
change in the outer contact rocks; Siwalik conglomerates abutting against it all along the 
Kangra Dun. 
There is still a leading feature of contrast between the two regions separated by the 
Jamu hills. In the Simla region the Subathu beds rest on a deeply denuded surface of the 
next oldest strata, supposed to be of lower secondary age; whereas beyond the Jhelam no 
such unconformity has been observed. This, it is evident, is a difference of precisely the same 
character as those already noticed within the tertiary series; and it is very noteworthy that 
these changes coincide in position with the most remarkable bend in contour of the bouudary 
of the higher mountains, formed of old rocks, where for a length of nearly eighty miles it runs 
north and south, making an angle of 45° with the general course of the range. The direct 
continuity of the outermost base of the hills bounding the plains is maintained, past this 
bend of the higher mountains, by a greatly increased width of the fringing belt of the 
tertiary rocks. 
These leading features of the two regions, as partially sketched in the preceding para¬ 
graphs, have been for some time more or less fixed ; and the interpretation I have put upon 
them is simply that the disturbances marking the Himalayan system, as displayed in the 
centre of its area, are of earlier date than those affecting the terminal portion 'and the 
Hindu Kush; that in early or middle secondary times a general elevation occurred of 
the south Himalayan area, along the border of which the Sirmfir deposits subsequently 
took place; that the eocene period was closed by the more special disturbance with crushing 
which constituted, perhaps, the principal phase of the mountain formation; that after a period 
of denudation the Nahan deposits set in; that a similar interruption produced the break 
between the Nahan and Siwalik groups ; while during all that time little or no elevation took 
place in the region of the Jhelam. Our observations in the Jamu hills have not disturbed 
these conjectures. 
During the past cold season I had the advantage of going over part of my old ground, 
from the Satlej to the Ravi, through the Jamu country, and over a part of the trans-Jhelam 
districts, in company with Mr. Theobald and Mr. Lydekher. The snow prevented us follow¬ 
ing the innermost tertiary boundary along the flanks of the Pir west of the Chenab; hut 
this was not our principal object, and Mr. Lydekher is now engaged in examining that 
ground. We satisfied ourselves that on the Satlej there is no assignable break, faulted or 
otherwise, in the sequence from the Nahan to the Siwalik strata, although a very approxi¬ 
mate position (that given in my map) can bo made out for the change from the harder, 
deeper-coloured clays and sandstones of the former, to the paler or brighter and softer rocks 
of the fossiliferous upper group. This distinction is more or less discernible throughout the 
whole range to the north-west. It may be very well seen on both sides of the Bakrala ridge 
between Jhelam and Rawalpindi. 
As might be expected from its much greater magnitude, the middle tertiary break—that 
appearing in the Cis-Satlej region as a Nahan-Sirmur contact, and in the Kangra district 
