Chap. 5.] w. blanfokd^ western india. 31 



existence of foliation amongst the granites^ the circumstance that no 

 general distinction can be drawn between true granites and the 

 more crystalline forms of the gneiss^ the lamination of which proves 

 its metamorphic origin, and the arrangement of the granite in lamellar 

 masses, constantly parallel to the gneissoid foliation, tend to show 

 that the distinction between the two is apparent rather than real, and 

 that the granite is an original constituent of the crystalline rocks and 

 not intrusive, but that in the course of metamorphism it has undergone 

 greater alteration than the gneissose rock, and crystallization has become 

 developed to so great an extent as to obliterate foliation. In treating of 

 the Bijawur and Champaneer beds it will be necessary to show the 

 Passages of Bijawur manner in which they appear to pass into the 



and Champaneer beds ^ j. i i 



into metamorphic rocks. gneiss, and the connection of the metamorphic 



foliation with the lines of cleavage will best be illustrated in the course 



of the same discussion. 



Foliation of the gneiss. — All observers of the metamorphic rocks of 



^ ^ . Bengal, so far as I am aware, have considered the 



Reasons for supposing '^ ' 



foliation of Bengal gneiss foliation of those beds to be in the planes of orio-inal 

 to he in the planes of x o 



original hedding. bedding. The reason for so doing is that the mineral 



distinctions in the rocks, as between gneiss, hornblend-schist, and quartzite, 



(distinctions which involve a difference of chemical constitution, and 



which may, with fair probability, be referred to original differences in the 



materials composing the sedimentary rocks now metamorphosed), appear 



to take place along lines coinciding with those of the foliation. This 



is apparent also on a very small scale : it is no uncommon circumstance to 



see, within the breadth of a foot or two, successions of laminse, quartzose, 



hornblendic, micaceous or felspathic, each of which may be traced for 



some yards. All appear to be lenticular, but the same is usually the 



case with fine alternations of different kinds of sediment amongst rocks 



of aqueous origin. 



.( 193 ) 



