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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-southwesterly course after being carried to the eastward by the unyielding 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 longitudinal and transverse synclinals.

Structural Features as shown in transverse sections.—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 systems of flexures. The areal geology of Horse Hill and Miles Hill in particular, shows that these properly secondary foldings