THE HO USA TONIC VALLEY. 785 



sericite and considerable graphite is sometimes associated 

 with it. 



The Egremont Limestone resembles that found along the 

 east base of Mt. Washington, its principal impurities being mus- 

 covite and quartz. It contains locally important layers of cal- 

 careous mica schist. In the vicinity of Twin Lakes, two distinct 

 beds of the latter are made out, one immediately below the 

 Everett Schist — a transitional zone- — and the other lower down 

 near the middle of the horizon. A third, less important and less 

 constant, zone forms a transition from the Riga Schist to the 

 Egremont Limestone. The upper of these layers forms the cap 

 of Babe's Hill (northeast of Washining Lake). The middle 

 layer is also found in the same hill along the southwest base, and 

 the lowest layer may be seen above the Riga Schist at the first 

 road-corner northeast of Chapinville. Graphitic phases are found 

 as a transitional zone between this horizon and the overlying 

 Everett Schist in the northeastern part of the area, particularly 

 in areas 16 and 25. 



The Everett Schist is not chloritic to any marked degree, as 

 is so often the case on Mt. Washington, but is frequently 

 sericitic, usually porphyritic from rounded eyes of feldspar, and 

 frequently passes downward into graphitic schist. 



EXPLANATION OF MAP. 



The map which accompanies this paper (Plate V.) is based 

 on the Sheffield and Cornwall sheets of the topographical atlas 

 of the United States, by the U. S. Geological Survey, and is 

 drawn on the same scale — 1 : 62,500, or one inch to the mile. 

 It overlaps by about one half mile the map which accompanies 

 the Mt. Washington paper. To bring as much of the area as 

 possible on the page, the narrow northern portion is placed in 

 one corner, its actual position being roughly indicated by the 

 positions of the Housatonic Railroad and the large marsh to the 

 west of it. Fig. 5 also extends the map some distance to the 

 south. The area covered by the Egremont Limestone is left 

 blank, while the Riga and Everett Schist areas are shaded, the 



