116 THE PENOKEE IROX-BEARING SERIES. 



facts, it is quite probable that the gabbros, syenites, syenite-schists, and 

 possibly the granites are parts of the same continuous rock-mass. 



The Eastern fjn'cn schist. — The shape of this area will be seen by 

 examining PI. ii. The exposures c-ontained are very numerous, and the 

 rocks within a certain narrow range have great variety. While quite large 

 subareas contain only a single phase of rock, they grade into other areas 

 containing rocks of a Uitferent character, and even a single exposure fre- 

 quently contains (juite dissimilar rocks. This confusion is so great that no 

 attempt will l^e made to subdivide the area into smaller ones, each contain- 

 'ing a detinite })liase of rock, nor will any attempt be made to explain the 

 field relations of the different jihases. The rocks liert- included may all be 

 teclmicall}' classed luider <nie general term — gneis.s — although perhaps some 

 of them might better be called syenitic schists and most are tine grained 

 green, crystalline scliistsi In these gneisses, aside from the (juartz and feld- 

 .spar, any one of the minerals hornblende, biotite, chlorite, sericite, or 

 epidote may be the additional chief constituent, while often two or more 

 are equally abundant. Consequently the area contains hornblende-gneiss, 

 biotite-gneiss, sericite-gneiss, chlorite-gneiss, epidote-gneiss, and various 

 intermediate phases. The rocks vary greatly in coarseness, running from 

 those that are so exceedingly tine grained that it is with extreme difficulty 

 that the minerals are determined, to rocks which apprt)ach a granitoid 

 gneiss. It is noticeable that the coarser grained phases are mostly found 

 near the granitoid gneiss areas. In fact the line . fornnng the boundary 

 between this schist area and the surrounding granite and gneissoid granite 

 areas is arbitrarily drawn. As the granite area is neared the schists become 

 coarser and coarser, grading into a coarse gneiss. The change is so gradual 

 at the east end of the area tliat the lx>undary l)etween the gneisses and 

 granites would probabl)' not be ))ut by another observer in the same ^jlace 

 as mapped. Tlie princi[)le followed in our mapping is to include within the 

 schist area all rocks which in hand specimen do not have a strong granitic 

 ap^iearance. While there is this change, it is not a passage which is made 

 out in any case by actually tracing a tinely schistose rock-mass in contin- 

 uous ex])osure into a grainte, but tlie various phases are presented by 

 numerous detached exposures. Aside from this ajjparent passage, the fine 



