. Annual report. New York State Museum; Science; Science. Il8 NEW YORK STATE MUSEUM of Triassic age in the Connecticut valley1 (figure 10). The accompanying photograph, plate 17 of the walls of Stark's knob shows the general structure. The fragment shown in figure 9, lying south of the fault, is more massive than the main stock, and the ground mass approaches more nearly the dense, dark basalt, but here are also developed amygdules. A hand specimen obtained here displayed fairly coarse crystals of plagio- clase, indicative of an intratelluric origin, such as are common in the diabase of many d
. Annual report. New York State Museum; Science; Science. Il8 NEW YORK STATE MUSEUM of Triassic age in the Connecticut valley1 (figure 10). The accompanying photograph, plate 17 of the walls of Stark's knob shows the general structure. The fragment shown in figure 9, lying south of the fault, is more massive than the main stock, and the ground mass approaches more nearly the dense, dark basalt, but here are also developed amygdules. A hand specimen obtained here displayed fairly coarse crystals of plagio- clase, indicative of an intratelluric origin, such as are common in the diabase of many dikes. This combination of the characteristics of dike rocks and of effusive explosive products makes Stark's knob one of the most interesting igneous occurrences, small as it is, within the limits of the State. Jointing of the lava crusts. The surfaces of the lava balls are beset with a network of cracks perpendicular to the surface. On exposed walls the lava crusts frequently fall to pieces in short, polygonal joint columns similar to basaltic Fig. 10. Sketch of a portion of the western wall of Stark's Knob, showing the gray, scoriaceous interior of the lava balls, the basaltic, jointed crust, and the fissile, devitrified, volcanic glass surrounding the lava balls The inclusions of limestone point to an irruption through the lower Paleozoic limestones which must occur in this field beneath the Hudson terrane. The inclusions may be appealed to as evidence that the trap came up through the Silurian and subjacent terrane, as held in this paper, and that the rock is not to be regarded as an in-faulted remnant of a lava flow once covering the Hudson terrane in this vicinity. Since Woodworth's study of the knob, the rock has been utilized for various purposes and largely quarried away. We visited it in 1910, in 1911 and in 1912. In 1910 active quarrying was in progress; in 1911 this was not the case but much material had 1Emerson, B. K. Diabase Pitchstone and Mud Enclosure
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