50 GEOLOGY OF THE SON VALLEY, ETC. 



greater or less distance up from the main stream, and there is every 

 indication that this valley is cutting backward and lengthening itself 

 at the expense of the eastern Adh, 



Before referring further to the Adh valley it will be well to con- 

 sider a miniature model of it which mav be 



Gorge at Khamerji. . J 



noticed on the map just north of Khamerji. 

 Here a deep gorge will be noticed penetrating about a mile into 

 the scarp, when it divides into two branches which separate at right 

 angles to the main gorge and penetrate in opposite directions for 

 about two miles to the west and one to the east of the junction. 

 On examining the ground above these gorges it is seen that they 

 are cut out of two open valleys whose position was determined by 

 an open synclinal fold in the Kaimur sandstones and whose bottoms 

 formerly lay at some 200 to 300 feet above the bottom of the present 

 gorge, and which after uniting drained northwards, through a valley 

 which can still be traced, to the Adh valley. 



This valley was evidently tapped by a gorge which cut back 

 from the south, its position being determined by a number of joints 

 and some small faults of a few inches throw, which traverse the 

 Kaimur sandstone just at this place. Having once cut back to 

 and tapped the drainage of the high level valley its volume and con- 

 sequently power was greatly augmented, the bed of the main gorge 

 was lowered and from its head branch gorges were cut back along 

 the beds of the streams which had now become its tributaries. 

 Once the drainage was diverted into the new course and the bed 

 of this lowered in consequence of the power added to the stream 

 flowing along it, any return to the old course became impossible. 

 At the present day there is a short gorge cut back along the old 

 course of the main stream, and in a direct line 



Diversion of drainage. , 



with the gorge through the Kaimur scarp. As- 

 cending from this by the steep slope at its head one enters a broad 

 open valley along the bottom of which an old stream-bed can be 

 traced, though now only occupied after rain by a much smaller 

 stream than that which formed it. Descending this, it is found to flow 



( 50 ) 



