736 THE JOURNAL OF GEOLOGY. 



Everett Schist. A somewhat striking lithological distinction, 

 which has been valuable for purposes of identification, is found 

 to separate the two schist horizons, the Everett Schist being 

 entirely free from garnet and staurolite, while the Riga Schist 

 usually (though not always) contains macroscopic crystals of 

 one or both of them. The older rocks are found in the southern 

 portion of the area, a general northerly pitch carrying them 

 successively below the surface as we proceed northward, until at 

 the north end of the mountain we find the upper two members 

 of the series only. 



The structure of the mass may be summarized by stating that 

 the beds have been thrown into corrugated folds which seem 

 to have moderate, tolerably symmetrical corrugations at the 

 south end of the mountain, but these corrugations deepen and 

 become frequently overturned as we proceed northward. In the 

 eastern portion of the area the axes of the reversed folds is gen- 

 erally westward. At the extreme south, the structure is a geo- 

 anticlinal, but this develops in the central and northern parts of 

 the area into a geo-synclinal owing to the continued dispropor- 

 tionate deepening and widening of one of its minor western 

 corrugations. The general pitch of the beds is north. A less 

 important southerly pitch which characterizes the northern 

 portion of the area, in combination with the general synclinal 

 structure in cross sections, gives to all the mountain except its 

 extreme southern portion a basin-like character. The rocks are 

 throughout strongly metamorphosed elastics, the orographic 

 disturbances to which they owe their marked crystalline character 

 and porphyritic crystals having operated in several distinct 

 periods. The Egremont Limestone shows a marked diminution 

 in thickness as we proceed southward in the area until it almost 

 disappears. Throughout the mountain plain it is greatly modi- 

 fied, being either a micaceous limestone or calcareous mica schist, 

 or a graphitic schist. The graphitic rock is most developed near 

 the schist contacts and in the southern portion is the only repre- 

 sentative of the limestone. 



Wm. H. Hobbs. 



University of Wisconsin, Madison, Wis. 



