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mass that forms the upper part of the ridge extending 

 from New Haven, into Massachusetts, commonly 

 called the West Mountain. This part of the ridge is 

 composed of trap or whinstone. In some parts it as- 

 sumes a columnar form, standing almost perpendicu- 

 larly. In others, it is composed of enormous broken 

 and shapeless masses of the same materials, slightly 

 connected, and easily broken up ; and among which, 

 may be found in abundance, splendid specimens of 

 phrenite, zeolite, &c. particularly in the neighbour- 

 hood of Simsbury. 



Among this latter kind of trap, a great quantity 

 may be found, filled with small spherical masses of 

 zeolite ; on being long exposed to the atmosphere and 

 changes of weather, the zeolite is probably decom- 

 posed and disappears, leaving a complete porous 

 mass which much resembles the bulleuse lava, and as 

 such, it is well calculated to impress a belief of its 

 bavins; been, at least, modified by the agency of sub- 

 terranean heat or fire. But all ideas however of this 

 kind are dispelled, when we examine the structure of 

 this mountain, and find, that its base for many leagues 

 in breadth, is composed almost entirely of old red 

 sand stone ; the most decided and unequivocal evi- 

 dence, on the contrary, of its Neptunean origin. 



The part in particular on which the ridge of trap 

 rests, is, in many places, considerably more elevated 

 than the adjacent country, particularly at New Grate 

 in the town of Granby, and having a dip or declina- 

 tion, of from thirty to forty-five degrees to the east. 



