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NEW YORK STATE MUSEUM 



consisting of a dozen such grains. It is possible that these came 

 from the grits. But if so, it is surprising that there are not larger 

 fragments from the same source, since these grits are exceedingly 

 tough and well-cemented rocks. 



Structural features. The dissection of the knob by quarrying 

 operations has brought to light some new structural features. 

 Woodworth described two faults along the margin of the knob, 

 and his section (figure 9) shows his conception of the rela- 

 tions of lava and shale. But quarrying brought to light other 

 masses of shale, involved with lava, within the knob. We found 

 evidence of severe compressive disturbance and dislocation all 

 through the lava mass of the knob, suggesting a number of minor 

 dislocations throughout the mass, instead of merely the two which 



Slates 



Fig. 12 Sketch of relations of shale and lava near the south end of the 

 knob; shale overlying lava on the projecting point at the left, and a steep 

 shale wedge in the lava midway 



he saw, which were all that could have originally been recognized. 

 A few sketches, and a comparison of them with our photograph 

 of the knob (plate 18), will aid in the presentation of the details. 

 Figure 12 is a diagram of the south end of the quarried face 

 of the knob, with a projecting point on the left which remains 

 unquarried. On that point, slate overlies trap. Woodworth's sec- 

 tion, in which trap overlays shale, was made a little farther south, 

 and the remnants may be seen just over the roof of the engine 

 house in plate 18. To the north of the point, shown in the sketch, 

 trap makes the full height of the face and the shale has pinched 

 out, but up this face runs another very steeply inclined, shale 

 wedge, which runs nearly to the top before pinching out. Because 

 of the section which Woodworth saw and figured, he judged a 



