120 THE PENOKEE lltON-BEAllING SERIES. 



In <4euera] tlic lu>rnl)lende, biotite, and chlorite are largel}' in tlie 

 spaces between the (juartz and feldspar, Ijut they also are extensi\ely 

 included within them, a sin^-le individual ot "one of these minerals perliaps 

 penetrating several ])ai"ticles of quartz or feldspar, or Ixith. Usualh' the 

 chlorite, biotite, and hoi-nblende are arranged with their axes more or less 

 regularly in a common <lirection. Sometimes this arrangement is but imper- 

 fect, while in otlier cases the parallelism is remarkable, the fibers of the 

 many individuals lying almost exactly parallel with each other. When 

 this parallelism is so marked it is sometimes the case that the (piartz and 

 feldspar particles are elongated in the same direction. Tliis elongation of 

 all of the minerals in such a, case doubtless indicates that the rocks have 



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been subject to great dynamic forces. 



Within these evenly granular gneisses are quite often larger grains of 

 quartz and feldspar, which have very distinct oval outlines. This is partic- 

 iilarly true with reference to the large quartz grains (PI. xv. Fig. 3), although 

 when examined closely they are seen to be minutel}' angulai'. As in the 

 roundish grains of the quartzose Ijackgronnd, no })roof lias been foun<I that 

 the (juartzes are of a fragmental chai'ai^ter. 



By a gradual lessening of the fpiartz in the hornblende-gneisst-s they 

 pass into a rock in which the chief constituents are hornl)lende and an alka- 

 lint^ fehlspar. These rocks might perhaj)s better be named s\'enite-schists. 

 In th(^ cases of some of them the lioi'ublende is ^'ery abundant; the feld- 

 spar closel\- interlocks, and the^' contain man\' iireas of black iron oxide, 

 which is d()ul)tless menaccanite^ as it is generally suri-ounded by a bril- 

 liantly polarizing reactionary ring suppo.sed to be titanite. These felds])ar- 

 hornl>lende-inenaccanite rocks in their mineralogical character are identical 

 with the syenites. 



They have not, it is true, in an\' case Vjeen traced in continuous 

 exposure to a r(;ck whicli lias the genuine syenitic texture, but ccmsidering 

 the fact that it has been ])roved tliat this class of rocks is in certain cases 

 derived from basic erujttivc^s, it becomes possible that tliese syenitic schists 

 are of this orio-in. 



A second jihase of hornblende-gneiss found abundantly in this area is 

 exactly like the hornblende-gneisses already described and illustrated (PI. 



