PHYSICAL GEOLOGY. 11) 



The cross drainage of the country, already alluded to, shows that 

 these ranges and valleys, instead of merely directing the flow of the 

 meteoric waters, as would at first appear, are themselves but the result 

 of its powerful and long continued abrading force. 



It is clear that the gaps through which the rivers now escape across 

 these ridges must have been commenced under a very different state of 

 things, at a time when the ridges, as such, did not exist, these and the 

 whole of the present surface being then buried beneath the soft strata 

 of the plains. 



There would seem to have been a depression over the valley of the 

 Tiri Taui from an early period, in gravitating towards which the streams 

 found it easier to deepen their former channels than to force a passage 

 through masses of the tertiary sandstone series towards either the Indus 

 or the Kuram. Notwithstanding this, the greatest effect of the meteoric 

 water in reducing the general level of the country was undoubtedly 

 produced upon these softer tertiary sandstones, &c. ; the harder limestone 

 and beds supported by it being left in relief, the present features of the 

 ground were thus carved from the mass. 



Structure of the ground. — Perhaps the easiest way to realize the 

 structure of the ground is to follow the more open and less disturbed 

 curves of the sandstone and argillaceous rocks occupying the valleys. 

 These, with many minor undulations, are found forming troughs, the 

 strata at the sides rising steadily, where not interrupted by dislocations, 

 towards the anticlinal ridges, and re-appearing with the same general 

 character in the valley on either side. From this it would follow that 

 the rocks of the ridges must be older, and as these, largely, if not entirely, 

 belonging to the same great tertiary formation, pass conformably 

 beneath the beds of the valleys, the simple alternation of anticlinal and 

 synclinal curvature might be expected to succeed. The case is, however, 

 different, the strata rising steadily towards the ridges become steeper, 

 vertical, and ultimately overthrown, so that along the sides of nearly all 



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