88 



CRUSHED LEDGES. 



FIG. 35. 



Fio. 36. 



Prof. Adams mentions another case in the southeast corner of Brattleboro, where 

 the laminae have been bent over in nearly the same direction as at Bruce's and Willard's 

 quarries, for the depth of only three feet. He also describes the same phenomenon in 

 two other quarries in Dummerston, belonging to Mr. T. Clark, only fifty or sixty rods 



apart. He thinks, however, that the direction of the crushing 

 force here must have been nearly opposite to that in Guilford 

 and Brattleboro. Recently, however, we found at the Dum- 

 merston quarries a spot (whether one of those described by 

 Prof. Adams we cannot say) where the force seemed to be 

 from the east, as shown on Fig. 35. The disturbance, so far as we could see, extended 

 only two or three feet vertically. 



An analogous case of fracture and crushing was found on the Western Railroad in 

 Middlefield, Mass., in hornblende schist, and described in the Massachusetts Final Report 

 with a figure (p. 396.) Also another case, less in vertical extent, within the city of Low- 

 ell, in gneiss, discovered in the grading of a street by Dr. S. L. Dana. 



During our researches in Vermont, other analogous cases have come under our observ- 

 ation. One of these is in one of the clay slate quarries in Northfield. It is on the 



north side of the ravine along which the quarries are opened, 

 and the accompanying sketch will give some, though a very im- 

 perfect, idea of the appearance of the edges of the slate, which 

 here have a westerly dip not far from 75, but which are bent and 

 fractured at the upper part quite as much as represented on the 

 figure. The force here must have pressed downward and west- 

 ward as at Guilford. 



A still more remarkable case occurs at Newbury, 

 two and a half miles north of the village, where 

 is a deep railroad cut through a variety of talcose 

 schist. The hill is a spur, forty or fifty feet high, 

 lying on the west side of the meadows, and its 

 narrowest part shooting out northerly. The strata 

 here, whose normal position is nearly perpendicular, 

 have been very much bent, broken, and crushed, to 



the depth say of thirty feet, which the railroad cut opens. It is diffi- 

 cult to convey any correct idea of these disturbances by the sketch, as the 

 faces of the rock laid bare coincide nearly with the strike of the strata. 

 The annexed imperfect oblique view of one spot on the west side of the cut, 

 (Fig. 37), will show something of the flexures, fractures and crushing, to the 

 depth of twenty feet. Sometimes the folia are bent at right angles without 

 any fracture. This may not have taken place wholly at the same time 

 with the fractures, as in other cases already described, at Bruce's quarry 

 of clay slate in Guilford, for instance, where movements of plication 

 along the nearly perpendicular joints seem to have taken place at an 

 earlier date than the fracturing force, and the bent laminae are rarely broken. 



FIG. 37. 



