120 MIDDLEM15S: GEOLOGY OF HAZARA AND BLACK MOUNTAIN. 



plain, where it is merging into the Mansehruh plain, the drainage goes 

 the other way and eventually joins with the Sirun river. Here the 

 nullahs are even more deeply cut down than on the southern part of 

 the plain, and they wind about between walls of clay and gravel, 200 

 or 300 feet high, in the same confusing way that they do in the 

 country south-east of Hureepoor. The cause of their deep channel 

 seems to be the same here as in the latter place, namely, the bare 

 nature of the slate hills in the vicinity, which are almost destitute 

 of all vegetation whatever. The rain in no case is held back for a 

 time, but immediately after a shower rushes madly down-hill, and 

 collecting into a fierce torrent scours out a passage for itself by cut- 

 ting vertically through the soft alluvium-. On this account the Sirun 

 river, like the Dore, is subject to sudden spates, and the crossing of 

 it at Khakee and Sher Ali Shah is often as uncomfortable a proceed- 

 ing as of the latter at Sultanpoor. Similar rushes of water caused 

 by the melting of the winter snow on the hills all tend to keep these 

 nullahs of the steep-sided nature that I have described. Much more 

 water comes from afar in the hills than from the near vicinity, for the 

 reason that much more rain falls on the hills than in the neighbourhood 

 of Abbottabad ; hence, in a measure and on a small scale, these little 

 deep-sided ravines are similar to the large canons so characteristic of 

 rainless areas. Still here, as in the Hureepoor plain, there must have 

 been a time during which the alluvium of this plain was being formed 

 instead of being cut away, for the plain and its deep channels are not 

 such as could be produced by streams alternately eroding and 

 depositing. 



It would seem as if this change in the nature of the action of the 

 streams might have been brought about by a general elevation of the 

 country within recent times, which, having steepened the river and 

 stream gradients, would have caused denudation to go on where 

 before was deposition, and deposition to be relegated to a lower level. 

 But there is also a possible cause in the demolition of the forest 

 which, no doubt, went on over all these tracts of what is now bare 

 hill-side in the earlier periods of man's occupation of it. 

 ( 120 ) 



