STRATIGRAPHICAL ELEMENTS: CRYSTALLINES, ETC. 85 



historical strata ; in other places highly metamorph- 

 osed and presenting all the characteristics of the most 

 perfect crystalline schists. The question whether any 

 of these are archsean remains open. 



(2) A great intrusion of acid granitic magmas on an immense 



scale among the lowest sedimentary rocks, bringing 

 about the metamorphism just referred to, and laying 

 the foundations of the mountain backbone of the 

 Himalaya and Hindu-Kush ranges. This acid magma 

 there is evidence for believing to have been forced 

 into the covering sedimentary rocks in Pre-Triassic 

 times and in two ways : (a) leisurely, under no particular 

 pressure probably, and without causing extreme meta- 

 morphic changes in those rocks ; and (b) by an in- 

 fective process, probably under enormous pressure, and 

 bringing about a complete metamorphism of the strata 

 and permeating them in a most perfect way. 



(3) A subsequent mild intrusion of dykes of basic rock, which 



have cut through the Infra-Trias sedimentary rocks, 

 through the schistose series, and through the gneissose- 

 granite, without leaving exposed anywhere in Hazara 

 known to me, any hemi-crystalline or glassy represent- 

 atives of subaerial lava flows. 



(4) The presence somewhere up the valley of the Indus river 



in at present unknown country of a more plutonic 

 representative of these dyke rocks, namely, a coarsely 

 crystalline granular rock shewing passage forms 

 strictly analogous to those of the dyke series in 

 Hazara. 



(5) The presence also in that unknown country of an ultra- 



basic division of rocks and some serpentinised varieties. 



(6) A wonderfully complete dynamic metamorphism of all 



the series of crystalline and metamorphic rocks, 

 wherever palpable evidence could be gathered ; which 



( 85 ) 



