

264 



BULLETIN OF THE 



noticeable that the hardness of the lower sandstone 'docs not depend 

 entirely on its distance from the trap, but rather on its composition. 

 A sandstone stratum, some twenty-five feet below the contact, is red 

 and very hard ; then comes some softer red shales ; above these some 

 soft gray shales, and finally, next to the trap, several feet of hard red 

 sandstone. The strata strike N. 25° E. ; dip 20^ E. S. E. The two 

 rocks here are very firmly welded together at their junction ; the line 

 is slightly irregular, but its average conforms precisely with the bed- 

 ding. Within a foot of the contact, the sandstone is somewhat vesic- 

 ular ; within an inch, its color changes to light gray, and in texture it 

 becomes a firm dense quartzite. The adjoining trap is dark and dense, 

 and but slightly amygdaloidal. The rest of the cut is all in trap, but 

 the rock is by no means of uniform structure. There is first a mass 

 from twenty-five to thirty feet thick (at right angles to dip), of which 

 the greater part is ordinary dense trap ; but its upper six to eight feet 

 become very amygdaloidal and loose-textured, and the upper limiting 

 line, clearly seen on both, sides of the cut, dips closely parallel to the 

 sandstone strata ; near the bottom of the cut it exhibits some irregu- 

 larity. Over this, but separated by an open seam, comes a second mass 

 of dense trap, of about the same thickness as the first. This is not so 

 decidedly amygdaloidal as the first in its upper part, and is limited 

 above by a very even six-inch band of coarsely crystalline trap, dis- 

 tinctly visible on both sides of the^cut. Ten feet higher, there is an- 

 other coarsely crystalline band, four inches thick, then say eight feet 

 of massive trap overlaid by drift ; no upper sandstone could be found. 

 These even persistent bands dip parallel to the sandstone; they are 

 rather abruptly interpolated in the trap, and the whole is firmly welded 

 together. I do not feel satisfied with any suggestion yet presented in 

 explanation of them ; but there can be little doubt that the lower mass 

 with its amygdaloidal cover is a single lava flow, buried under later 

 eruptions. One can hardly imagine a clearer example of the kind. A 

 number of small faults-can be seen on the sides of the cut, well marked 

 by a foot or. so of brecciated trap ; the fault planes are all at right angles 

 to the dip of the ^sandstone; the largest throw was only a foot, with 



uplift on the east. 



I have been unable to connect trie ridges here with the single poste- 

 rior range by Mount Tom, and cannot say how they arc related to one 



another. 



D. Becldey, Conn. (fig. 39). — The several curved ridges shown on 



Percival's map (1, 2, 3, north end of E. III.) in the towns of Berlin and 





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