444 THE PENOKEE IllON-BEARING SERIES. 



Tlie iiarrowuess as well as the periiiaiience of the Quartz-slate mem- 

 ber is strongly brought out by PI. ii. Here is a belt of rocks which iu 

 surface width is upon an average not more than 400 to 450 feet, and the 

 thickness of which is not more than 350 to 400 feet. Its maxinnim thick- 

 ness east of Sunday la-ke is not more than 800 feet. In chapter iv the re- 

 markable essential likeness of the various parts of this belt is indicated. 

 Its southern part is a layer of green, brown, gray and red quartz -slates. 

 Its uppermost layer is a vitreous quartzite. In whatever part of the range 

 a section is made across the belt, its essentially fragmental character is at 

 once discoverable, the rocks being comparatively little changed since they 

 were originally deposited. Tlie induration of both the quartzite and the 

 slates has been explained to be due to the enlargement of quartz-grains 

 and to metasomatic changes of the feldspar. 



Unconformity between the Southern Complex and the overhjinfi Cherty 

 limestone and Quartz-slate. — There is, then, between the Quartz-slate and 

 the rocks to the southward the great fundamental difference between rocks 

 Avhich are easily provable to be of clastic origin and those which are com- 

 pletely crystalline schists and massive 6ruptives. There can be nowhere a 

 wider lithological difference in the characters of two sets of rocks than this. 

 But more remarkable than the lithological simplicity of the Quartz-slate are 

 its straightforward field relations. This slate once seen is easily recognized. 

 It always dips northward, varying within narrow limits. Take the strike 

 of cuw ledge and follow the direction either to the east or to the west with 

 a little latitude of movement and almost invariabh' another ledgfe of like 

 I'ock is found within a slioi-t distance if exposures are at all plentiful. Tlie 

 only part of the area in which natural exposures within the belt were not 

 found has been penetrated and exposed by mining operations, so that its 

 continuity can be with certaintv asserted. It is true it bows locallv from its 

 general course, and in two or three places it is somewhat faulted, but the 

 variation is never sufficient to lose the belt. As one traverses this range 

 north and south at sliort intervals, the conqjlexity and variety of the litholog- 

 ical characters and of the strikes and dijis of the roc-ks of the Southern Com- 

 plex and the likeness, simplicity, directness, and uniformity of this slate 

 belt now just mirth of the granites and now in contact with the crystalline 



