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vicinity of the trap, there occurs a considerable quantity of the 

 sulphate of baryta, scattered in detached pieces over an area of 

 perhaps a fourth of an acre, which is nearly barren of vegetation. 

 Precisely the same circumstances exist in a locality of the same 

 mineral, in Bucks county, Pennsylvania ; the sulphate of baryta 

 lying adjacent to the trap, and giving rise to a remarkably sterile 

 soil. 



In some deep borings made at New Brunswick in search of 

 water, it is evident, from the description given of the materials 

 which were encountered, that more than one narrow dike or 

 perhaps bed of trap rock was met with, whose outcrop on the 

 surface has not been detected.* 



Rocky Hill and its Prolongation. — The next trap belt, interesting 

 from the phenomena connected with it, is that of Rocky Hill. 

 Commencing at its eastern termination near Lawrence's brook, 

 we observe the shale on both sides to assume, as we approach 

 the dike, a bluish colour, and an extremely compact structure- 

 On the southern declivity of the hill it is of a purplish or cho- 

 colate tint, and excessively hard and tough. It is studded 

 throughout with small spherical knots or crystalline nodules, 

 consisting apparently of the minerals epidote and hornblende, in 

 a state of incomplete crystallization. This belt of altered shale 

 extends from a point about half a mile southeast of the straight 

 turnpike to the Millstone river, which it crosses at the foot of 

 Rocky Hill, near Kingston. The changes induced in the whole 

 lithoid character and structure of the shale, by the intruded 

 igneous rock, are very finely exhibited along the canal, at both 

 the northern and southern bases of the Rocky Hill dike, evincing 

 a curious gradation in the crystalline action, as we approach the 

 trap. 



Near the southern base of the ridge, the red argillaceous sand- 

 stone displays the series of changes already noticed, its colour 

 becoming deepened, and dark crystalline knots or kernels abound- 



* I may here mention as adding another locality to the numerous ones already 

 observed, both in Europe and this country, showing the increase of the earth's 

 temperature as we descend, that in one of these artesian wells, the water derived 

 from a depth of 175 feet being 52° Fahr., upon reaching a depth of 275 to 300 feet, 

 its temperature was 54° Fahr. This last is exactly the permanent temperature of a 

 fine natural spring, which issues from the side of a hill about a mile southeast of 

 the town, 



13* 



