PUNJAB OIL REGION. 



7 



(nummulitic) rocks; and the same maybe said of many of the smaller streams, 

 especially of the very striking series of small side streams of the northern feeders of 

 the Sohan. 



In a district where the rocks dip gently, their basins, as they are wider than in one 

 of steep dips, are likely to be longer also and less decidedly broken up by subordi- 

 nate folds, and the saddles between less broken up and crushed together. The valleys 

 are therefore more likely to be long and the ridges unbroken ; and in the course of 

 time, after the first UTegularity caused by the comparatively quick wearing down of 

 the main channels to their lowest level, there becomes great uniformity in the shape of 

 the valleys, long, narrow, and parallel, and in the crests of the mountains long and 

 level. The valleys form ravines rather than gorges ; for they are not extremely steep 

 on both sides for any great distance. The mountains about Aluggud show these 

 features well. Such mountains in wearing away to the final dead level will become 

 more and more gently rounded ridges, the country will become more and more open, 

 and at length quite flat. 



Where the rocks, however, dip very steeply and have been much crushed together 

 and overturned, the small basins are more likely to var}' the drainage of the large 

 ones, there are more chances of cross breaks and numerous cleavage planes ; so that the 

 valleys are shorter and more irregular, and the mountains rise in peaks rather than in 

 long crests. So it is in the sjmr of the Himalayas, in the Choor Hills and in the 

 western end of the Salt Range about Jaba near the Indus. In wearing away, such 

 peaks may become more and more rounded, until they sink to the level of the ^'alleys 

 and the country becomes flat. 



4. The topography is somewhat affected by the nature of the wearing agent, 

 whether this be the wind, {a) the rain, (h) rivers, {c) the sea, [d] frost, or (e) ice. 

 But no part of this region would seem to be affected materially by the wearing or 

 carrying power of the wind, unless it be some light, sandy portions of the low country 

 south of the Salt Range. 



a. The rain of course falls equally on the hilltops and on the plains, and loosens 

 more or less of the rocks or earth it falls on, accordino: to theii* hardness, and carries 

 the loosened particles with it to the streams and towards the sea, more or less accord- 

 ing to the steepness of the surface. Whei-e a harder bed covers a soft one, this will 

 be, as already remarked at Aluggud and elsewhere, cut to an upright wall around the 

 edges of its shelter. The action of the rain is, then, that of washing. Its effect can 

 be seen everywhere through the region. 



b. The action of rivers on the other hand is not merely that of washing, in the same 

 way as rain, l)ut of undei'mining ; for a stream often washes away the bottom of a 



