joining figures, taken from sections now removed, west of Amsterdam Avenue, at 78th Street (Figs. 8 and 9).
Striking
developments of granite venation (probably dikelike in origin) can be
seen in the rock bluff at the head of 130th Street and St. Nicholas
Avenue.
The
feldspar of all the granite veins varies in color from white to pink
orthoclase and a delicate green oligoclase, which under a low
magnifying power displays the straight rulings of polysynthetic
twinning, viz., the striae like the finest lines produced by the contact of many individual plates of the min-
