No. 104.] 169 



anticlinal, the strata on the north-west slope and on the crest dipping 

 steeply to the north-west ; on the south, to the east-south-east. On the 

 section over Big Stissing the dips are to the north-west from the crest 

 down the western slope, and to the east-south-east on the east and 

 steeper slope. The same change in the direction is to be seen crossing 

 the mountain on a west-south-west course from J. A. Thompson's place, 

 one mile south of Stissing lake. The predominant strike is to the north- 

 north-east and the aVerage inclination is 70*^ to 75*^ — ranging, in the 

 observed cases, from 60'' to vertical. But a much more detailed ( 

 survey of the surface is needed to ascertain the position of the out- 

 cropping strata and to bring out the lines of folding and faulting and 

 the general structure of this isolated range of crystalline rocks. 



The prevailing types of crystalline rocks in Stissing mountain are 

 gneisses, granites, granulyte and syenite. The most common variety of 

 gneiss is a moderately fine crystalline aggregate of orthoclase, translu- 

 cent quartz and muscovite. The feldspar is white to flesh-colored, and 

 with facets up to -^^ inch ; the quartz is glassy to milk-white and appar- 

 ently filling in the spaces between the feldspar ; the mica is in fine 

 white to brown scales, which are disposed generally in lines or thin 

 lamims through the rock mass. A black mica (biotite?) is found 

 accompanying the muscovite in nearly all of the gneisses. And it 

 might be termed a biotite-muscovite gneiss. The varying propor- 

 tions of these constituents make up an almost endless gradation — 

 from feldspathic to quartzose and micaceous gneisses. So far as macro- 

 scopic observations go there appears to be a predominance of mono- 

 clinic feldspars, although the triclinic were detected in some of the 

 specimens studied. 



Granulyte and pegmatyte occur, but are much less common than 

 the gneisses. The former has generally a very slight percentage of 

 mica in it. Granite and syenite also are to be seen, but confined to 

 small outcrops, some of which are, probably, intrusive, cutting across 

 the bedded gneisses. 



In places the presence of a large percentage of mica gives the rock a 

 schistose appearance. And these micaceous gneisses alternate irregu- 

 larly, and are interbedded with the more feldspathic and granulyte 

 strata; or, they are confined to narrow belts or bands in the more com- 

 mon gneiss. They are thinner bedded also, and the stratification is 

 more distinctly marked in them by both the arrangement of their con- 

 stituent minerals and the planes of bedding. The grey, feldspathic 

 gneiss occurs usually in thick beds, and often the stratification is recog- 

 nized by the lines of minerals only. But there are comparatively 

 limited areas of the unstratified or massive rocks, or those in which the 

 bedding cannot be seen. No attempt was made in this survey of the 

 range to define the limits of these areas of indistinctly-bedded and 

 massive rocks. 



The Stissing mountain gneisses and associated crystalline rocks 

 resemble closely those of the Highlands of the Hudson. Although 

 identification of age based upon lithological resemblances is not as 

 satisfactory evidence as that from palreontological characters, still the 

 relation to the overlying quartzite, the similar structure and the gen- 

 eral /aci^s of the whole appear to justify us in assigning them to the 

 same geological age. Stissing mountain may, therefore, be considered 

 [Assem. Doc. No. 104.] 22 



