151 



quarry remarkable for the distinctness and size of the green 

 spheroidal masses of epidote. The degree of baking which it 

 seems to have received even at this distance from the trap, has 

 given it a closeness of texture which fits it finely for purposes 

 requiring a durable building stone. Near the same quarry, the 

 rock contains a narrov/ band of nearly pure epidote, about an 

 inch and a half thick. Beyond this second quarry, towards 

 Griggstovvn, the rock soon assumes its usual soft slaty texture 

 and deep red colour. 



The zone of altered shale, having the structure above described 

 at the Millstone river, extends particularly along the northern 

 flank and base of Rocky Hill, to its western termination, rising 

 high on the slope of the ridge, whose southern crest alone contains 

 the trap. 



North of Princeton the southern belt of the altered rock lies in 

 a lower ridge, parallel with the ridge of trap, but separated a 

 little from it, the intervening depression having resulted from the 

 comparatively easy disintegration of the highly altered rock 

 lying directly in contact with the trap. When we trace this belt 

 of discoloured shale westward, we find it disappearing before we 

 quite reach the termination of the prominent portion of Rocky 

 Hill, whose actual termination is, however, much beyond the 

 point indicated on the map. It forms, in fact, a continuous 

 though irregular chain with the trap hills east of Herbertstown. 



Near the head of Jacob's creek, at the abrupt termination of 

 one of these trap hills, there is an old mine, where excavations to 

 some extent have been made in search of copper ore, the rubbish 

 discharged from the diggings, showing some traces of that metal. 



The same series of nearly continuous dikes extends to the 

 Delaware, forming two conspicuous elevations near the river 

 called Smith's Hill and Belle Mount. In this western portion of 

 the belt the trap has produced effects on the shale and sandstone 

 similar to those seen along Rocky Hill. Upon Moore's creek 

 the strata are much altered, having a dark bluish or purple 

 colour, and being excessively indurated. Their nearly black 

 hue, when wet, has led to the notion that these shales are the 

 dark carbonaceous slates of a coal formation. 



In the hill called Belle Mount the trap rock is well exposed, 

 having been excavated in making the feeder of the Raritan canal. 



