33 



GEOLOGY OF THE SON VALLEY, ETC. 



plateau, but causes its scarp to recede by the breadth of the slice of 

 the hard bed removed. 



Fig. 2. 



Taking now the case of a dip of 45 as represented in Fig. 2, it 

 will be seen that the removal of an equal amount of the hard bed 

 causes the crest of the ridge to recede, but not to the same extent as 

 in the case of a horizontal dip, while the crest is at the same time 

 lowered. For a dip of 45 the change of height and the horizontal 

 shift are equal, for other angles they will be to each other in the ratio 

 of the sine to the cosine of the angle of dip. For angles less than 45 

 the horizontal shift exceeds the vertical lowering, and for angles above 

 45 the reverse is the case, the amount of lowering becoming greater 

 and the horizontal shift becoming less till we reach the condition of 

 vertical dip represented in Fig. 3. Here the removal of the hard bed 

 has no effect whatever on the position of the ridge, but its height is 

 lowered by the whole amount of the slice removed by denudation. 



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