152 



It possesses less of the basaltic character than belongs to much 

 of the trap in the Newark ranges. It is of a gray colour, rather 

 coarse texture, and consists of a large proportion of felspar, 

 united with augite, and is therefore a true dolerite or augitic trap. 

 Some portions contain hornblende instead of the augite, being in 

 these cases the rock called greenstone trap. These two varieties 

 are distinctive of nearly all the belts of this rock in this neigh- 

 bourhood, including the important one of Goat Hill. 



Sourland Mountain. — The next zone of trap and altered rock 

 •which claims our attention is that of the Sourland Mountain and 

 its prolongation. Goat Hill. This lies northwest of the belt just 

 described. Viewing the general topographical features of the 

 Sourland Mountain, and the wide plain of red shale and sand- 

 stone around its base, from any part of the Somerville trap ridge 

 distant several miles, we are led to some interesting reflections 

 regarding the small degree of violence which has accompanied 

 the protrusion of the trappean rocks of this region generally. 

 Standing on the large rubbish banks of the old Bridgewater 

 copper mine, where we are elevated scarcely one hundred feet 

 above the general surface of the wide level tract of red sandstone 

 spreading to the south, southwest, and west, we overlook the 

 country for a great distance, and behold the Sourland Hill rising 

 like a broad solitary island from the smooth surface of the 

 extended plain. The very features of the scene are enough to 

 indicate the absence of any great convulsive disturbance of the 

 strata during the outpouring of the trap, which seems to have 

 made its way to the surface through a series of long and narrow 

 fissures, produced by the mere gaping asunder of the rocks, and 

 not, as in some regions, by enormous vertical disruptions and 

 irregular uplifting movements, imparting invariably a broken or 

 undulating contour to the scene. 



In the Sourland Mountain the trap rock is confined chiefly to 

 its broad rounded summit, forming the axis of the hill; while, 

 from this position to beyond its base, reposes, on each side, in 

 undisturbed and regular stratification, a thick belt of the indurated 

 and baked shale. On the northwestern flank of the mountain, 

 towards Flaggtown, the rock in some places shows striking 

 evidence of the intensity of the igneous action, for it has all the 

 aspect of the fused slag or cinder of a furnace. Portions of it 



