Geology^ if/r. of the Connecticut. 53 



such a variety. A locality of it ma> be found one hun- 

 dred rods north of the Deerfield nvt ? bridg > in Deertield, 

 al the western foot of the trap ran-ie. 



The columnar tendency of our greenstone has often been 

 noticed. It may be seen in ahno?t every ridge in a great- 

 er or less degree, on the mural face — and these columns 

 are sometimes remarkably regular. Good examples of them 

 occur on the south-west face of Mount flolyoke ; and still 

 better ones a mile east of the village of Deerfield, a quarter 

 of a mile north of the locality of chabasie, analcime, &c. men- 

 tioned in the Jour, of Science Vol. I. p. 115. They have 

 from three to six sides, are articulated, the points varying 

 from one to three feet in diameter, and of the same height, 

 exhibiting handsome convexities and corresponding concav- 

 ities. Haifa mile south of this spot may be seen columns 

 curving to the right and left as they ascend ; thus forming 

 a portion of an arch. The geologi^^t, who traverses this 

 ridge, can hardly avoid traversing in imagination the giant's 

 causeway, StafTa and the Hebrides. 



Some of the less perfect columns have a remarkably fis- 

 sile tendency ; forming good hand specimens of pseudo- 

 green-stone slate. Globular distinct concretions of this 

 rock are not unfrequent among the amygdaloid ; composed 

 of concentric coats of greater specific gravity than the rest 

 of the rock. I have noticed them in Deerfield, and on the 

 New-Haven turnpike between Durham and Northford, they 

 are abundant, and from two to twelve inches in diameter. 



The general aspect of our greenstone, where it has been 

 long exposed to the weather, is reddish brown. When 

 newly broken it is greenish, often somewhat lively. Some- 

 times it is greyish black, and, very rarely, has the color 

 of a brick that has been burnt very hard. This variety is 

 compact and the felsparimperceptible. It is often the fact, 

 indeed, that the two ingredients in other varieties, are not 

 to be discovered by the naked eye, or with an ordinary lens. 



A question then occurs, whether some of the varieties of 

 this rock are not genuine basalt ? Certainly some of them 

 answer the description of that rock, so far as external char- 

 acters are concerned, to say the least, as well as of green- 

 stone. And, indeed, if "greenstone and basalt may not 

 unfrequently be seen passing into each other in the 

 same stone, as D'Aubuisson and Dolomieu have observ- 

 ed," (Bakewell's Geology, p. 11 9,) there seems no rea= 



