Chap. 5.] w. blanford^ western india. 33 



Not only is the strike thus singularly constant, but to it are parallel 



all the great features of the country, the hill 

 Parallelism of great 



featm-es of the country ranges, many of the trap dykes and all the prin- 



to the foliation-strike. • i n i jt -n i t 



cipal faults.* Even the hue of the Nerbudda valley 

 itself is in the same direction. It is a curious circumstance moreover 

 that this valley loses its peculiarly defined outline on the north side, and 

 the scarp, which stretches almost uninterruptedly from north of the Sone 

 and Nerbudda valleys near Sasseram in the valley of the Ganges to Bagh, 

 ends at the spot where the direction of the gneiss lamination changes. 

 Now, bearing in mind the persistent verticality of the gneiss, this 

 constancy of strike would be a most abnormal cir- 

 posing foliation in cumstance if the foliation were in the original 

 ^^^ "' planes of the bedding. It would show that while 



the rocks had undergone such enormous disturbance that their originally 

 horizontal beds had become vertical, that disturbance had nevertheless 

 been so regular that their strike had never altered. This is certaiijjy 

 not usually the case with rocks which have undergone great disturb- 

 ance. As a general rule, their direction is far from regular, and their 

 dip in the last degree variable. 



On the other hand, the constancy of the strike and the persistency of 

 the high dip are characteristic properties of cleavage. 



Characters of dip and 



strike of foliation those The exceptions to the ruling direction are not more 



of planes of cleavage. , ,> . i i 



numerous than might fairly be expected to have 



arisen from the subsequent disturbance which has affected the region, and 



evidence of which is found in the Vindhyan and other later formations. 



This, however, is only one argument in favor of the foliation of the 



metamorphic rocks being due to cleavage. The 



Parallelism of gneiss , . , , . tj. • j-i, c i. i 



foliation to cleavage of most important remains. It is the periect paral- 

 Bijawui-s. lelism everywhere existing between the foliation of 



the gneiss and the cleavage lamination of the Bijawur beds. 

 * See Mr. J. G. Medlicott's report and map passim ; M. CI. S. I., Vol. II. 



E ( 195 ) 



