PHYSICAL GEOGRAPHY. 51 



over a gentle slope and through an open valley, showing no signs of 

 erosion, as the present stream is quite unable to move the boulders 

 left by its predecessor. After passing for some distance along this 

 marked signs of erosion commence, the stream-bed is deeply cut^ 

 has a much steeper gradient, and is blocked by large angular blocks 

 of stone ; there are, in fact, all the signs of active erosion and of a 

 recession of levels along the stream-bed. Further down the gradi- 

 ent decreases and a boulder-strewn stream-bed reaches down to the 

 Adh. Here we have the stream cutting its bed backwards from the 

 recently lowered bed of the Adh which it joins, the change of level 

 at the junction having been too recent to allow of the recession of 

 levels having reached the watershed and so established a uniform 

 slope throughout the length of the stream-beds. 



Returning to the western Adh we may suppose that the east- 

 Origin of the Narkuni ern Adh was once a part of a valley and 

 gorRe * whose head waters lay twenty miles or more 



to the west. Then, near where the village of Tikat now stands a 

 ravine cut its way back through the Kaimur scarp and tapped the 

 upper waters of this stream. As a consequence of the increased 

 power so obtained it rapidly deepened its bed, and from the lower 

 level so established a tributary ravine began to cut back eastwards 

 till at the present day it has attained a length of twelve miles, and 

 as we have seen, seems still cutting its way backwards at the 

 expense of the eastern Adh. 



The very few other tributaries of the Son which penetrate the 

 other valleys due to cut- K * imur scarp are all quite insignificant in size, 

 ting back. and al | have been most unmistakably formed 



by cutting back from the low level of the Son valley. This being 

 so, it is natural to suppose that the valley of the Ghagar, whose 

 aspect is quite compatible with a similar origin, was also formed in 

 this way. 



We now come to the consideration of the antiquity of the east- 

 Antiquity of the Son to-west portion of the Son valley, and of its 

 va ey * continuation above the bend in the Mahanadi 



E 2 



( 51 ) 



