43 GEOLOGY CF THE SON VALLEY, ETC. 



From these considerations it is seen that the most continuous 

 ridges should be formed by beds dipping at about 45 ; where the 

 dip is low there will be flat-topped scarps, showing much irregularity 

 of outline in detail ; where the dip is high there will be a straight 

 ridge, rising into peaks and crags, but interrupted by low gaps. 



This is exactly what is found to be the case, the scarps of low 

 Agreement with observed dipping Vindhyan and Gondwana rocks show 

 facts * great irregularity of outline in detail, even 



-srhere they exhibit a marked constancy of general course. In the 

 lower Vindhyan area, where dips of from 40 to 6o° are found, 

 the long, straight and continuous ridges are a marked feature, and 

 in the transition area, where higher dips are the rule, we find the 

 ridges very uneven in height, rising into peaks separated by deep 

 saddles, which often descend nearly or quite to the level of the 

 low ground between the ridges. 



As in all areas which have been exposed to subaerial denudation 



for any length of time, there are numerous indi- 

 Diversion of drainage. 



cations of changes in the course of the 

 drainage, and the ridges are pierced by " wind-gaps," marking 

 places where they had once been traversed by streams which have 

 now been directed to other courses. One such is represented on 

 Plate 1, and another case may be noticed where the diversion of 

 the drainage is not quite complete. 



About fifteen miles east of the junction of the Banas and Son rivers, 



Kushmahargap. and of th e point where their combined waters 



pass through the ridge of the bottom quartzites 



of the lower Vindhyan series, the map shows a small stream flowing 



through the continuation of this ridge and draining a small area near 



the village of Kushmahar. The gap through the high ridge is, 



however, not in keeping with the size of the stream which now flows 



through it ; instead of being a narrow gorge it is an open valley 



through which one of the principal tracks of the neighbourhood runs 



and at whose bottom flows a small streamlet quite incapable of 



forming so large a valley, or even of keeping open a valley through 



this ridge of hard quartzites. 



( 40 ) 



