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are excessively hard and tough. At the base, near the northern 

 termination of the hill, the shale still manifests a great degree of 

 induration; it is of a blue colour and compact grain, but retains 

 its slaty structure sufficiently to fit it excellently for flagstones, 

 for which it is quarried. The condition of things in and around 

 the Sourland Mountain is well seen by crossing it northward from 

 the little village of Hopewell, near its southeastern base. Imme- 

 diately north of Hopewell we pass over a ridge of little elevation, 

 at the base of which is a light gray arenaceous sandstone, easily 

 disintegrated, containing both the micaceous and brown oxides 

 of iron in considerable abundance. The summit and northern 

 declivity of this low ridge consist of blue shales somewhat indu- 

 rated. Crossing a narrow valley to the southeastern foot of the 

 main Sourland Mountain, we find its entire slope composed of 

 ihe shale in a highly altered state, being blue, compact, and 

 greatly indurated. It is excessively tough, difficult to fracture, 

 and produces a clear ringing sound when struck. The loose 

 masses often exhibit externally a peculiar glazed aspect, analo- 

 gous to that upon the surface of some kinds of slag. These 

 altered strata extend to the highest parts of the mountain. 

 Crossing a slightly depressed belt, the trap rock next displays 

 itself, and continues to the northwestern declivity, where it gives 

 place again to the altered rocks composing the other flank. The 

 whole mountain is thus formed of a series of nearly parallel 

 elevations, with more or less considerable intervening depres- 

 sions, or valleys, which are by no means regular, the single 

 axis of trap rock occupying a nearly central position. 



In the southwest prolongation nearly of the Sourland Mountain 

 we find the same or rather another almost continuous and parallel 

 dike, which passes a little south of Rocktown, and thence to the 

 Delaware, making there the axis of Goat Hill. This elevation 

 ranges about half a mile southeast of Lambertsville, and crosses the 

 Delaware in an oblique direction, appearing on the Pennsylvania 

 side below New Hope, where it displays some interesting pheno- 

 mena. Along the northwestern base of this ridge, on both sides 

 of the river, the strata dip as usual, but are affected in a striking 

 manner in their structure and composition for at least a fourth of 

 a mile from the trap. In the quarry northeast of Lambertsville, 

 we discover the commencement of the change. There the red 



