THE HOUSATONIC VALLEY. 789 



pears beneath the limestone as the most northerly outcrop of the 

 Riga Schist. The southern limit of the central crest of the eastern 

 undulation is at the south base of Tom's Hill, where the schist 

 disappears through a southerly pitch varying from 35 to 50 , 

 allowing the Housatonic River to take at this point a south-south- 

 westerly- course after being carried to the eastward by the unyield- 

 ing schist mass of the hill. The minor undulations of the 

 crest-lines of flexures within the northern part of this eastern 

 ridge, are beautifully shown, not only by the areal relations and 

 by divergence of strike observations, but also by the pitch of the 

 plications (cf. arrows on map). Within the central undulation 

 (Miles Hill), the same feature is indicated in the small basins of 

 limestone which are entirely enclosed within the boundaries of 

 the Riga Schist. The triple undulation of the western ridge of 

 the district has a perfect parallel on the east. To the southwest 

 of Tom's Hill just south of Washinee Lake appears an anticlinal 

 of schist, which continues to rise and broaden in going south. 

 The island in the lake is an anticlinal of the Egremont Limestone 

 where it mantles over the ridge of schist. From below the schist 

 anticlinal emerges the Canaan Dolomite near the southern margin 

 of the map. As would be expected, the caps of Everett Schist 

 which are found within the area studied, are widest opposite 

 where the ridges of Riga Schist disappear, i. e., where basins of 

 quaquaversal synclinals are formed by the coincidence of longi- 

 tudinal and transverse synclinals. 



Structural Features as shown in transverse sectiofis. — The 

 nature of the flexuring within the area studied is indicated in the 

 series of sections (cf. Plate VI). The types are the unsymmetrical 

 fold with shorter and steeper western limb, indicating an easterly 

 dipping axis, and the overturned or reversed fold with easterly 

 dipping axis less steep than the first. The western limb of the 

 sharper reversed folds has been ruptured, in some cases producing 

 rather steep thrusts of small displacement. The hade of these 

 faults is about 45 °. The main flexures carry also subordinate sys- 

 tems of flexures. The areal geology of Horse Hill and Miles 

 Hill in particular, shows that these properly secondary foldings 



