OUTLINES OF GEOLOGY. 



75 



tain bends and encloses a basin occupied by a lake, and hav- 

 ing the aspect of a volcanic crater. 



A few miles east of the Pallisadoe ridge are two others, 

 nearly parallel to each other, known by the names of the 

 first and second Newark mountains. The first terminates at 

 Springfield, the second continues to the south towards 

 Boundbrook, then turns west, and bending into the shape of 

 a hook, terminates at Baskenridge. These three ridges are 

 all overlying masses, resting upon sand-stone. The junction 

 of the trapp and sand-stone formations can be well examined 

 in the ravine at Paterson, through which the Passaic river 

 has made its way by taking advantage of a natural fault. A 

 fourth ridge rises near Morristown, and extends six or eight 

 miles to the southwest, and which appears to be a dyke. 



Adjacent to the Newark mountains is a basin nearly cir- 

 cular, and about three miles in diameter, enclosed on all sides 

 but one by a ridge of trapp. This, although now filled by a 

 level plain of alluvium, has also much of the aspect of a 

 crater. 



In Connecticut there are also many ridges of trapp. Those 

 which I have examined in the vicinity of Hartford differ from 

 those of Jersey, in being dykes. 



] 73. Trapp and Basaltic rocks are not only found in ver- 

 tical, but also in inclined prisms, and a bed of one of these 

 often rests upon the other. Of this there is also a good in- 

 stance at Paterson. 



174. Rocks of this order are occasionally found in globu- 

 lar masses, forming conical heaps. At Baskenridge, where 

 we have seen that the second Newark mountain terminates, 

 there is a heap of this sort imbedded in green earth. On 

 digging into this heap, it was found that the masses gradually 

 became angular, then truly prismatic, and finally merged in 

 a solid mass of trapp. The inference was obvious, that the 

 globular form had been caused by desquamation. 



