1*0 Geology, ^c. of the Connecticut^ 



Where the profile crosses this rock, some of the imbed- 

 ded masses appear at their surface as if they had undergone 

 the action of fire. On breaking a mass of gray quartz con- 

 taining a little mica, a zone of half an inch wide appeared at 

 the outer edge, of a brick colour, indicating a chemical 

 change either by fire or water, for the specimen was some- 

 times covered by water. 



I have observed little of this peculiar puddingstone in 

 Connecticut, though so abundant in the northern part of the 

 coal formation. It appears, however, in the south part of 

 Durham. 



No. 60, Gee5?^^covering a narrow valley. 



No. 61. A narrow stratum of gneiss. 



No 62. Granite — This does not appear in abundance ort 

 the bank of the river. The best spot for examining it is 

 half a mile south, where it forms a hill 100 or 200 feet high. 



From the preceding description of this profile, it appearS| 

 that after crossing the first ridge of greenstone there is a 

 gradual decrease of the dip from 45° to IS**, and after pass- 

 ing this point, which is not exactly central, but nearer the 

 granite than the greenstone, we find the dip in a contrary di- 

 rection, and almost 90°. Precisely such would be the ef- 

 fect, the Huttonian would say, if we suppose the granite and 

 the greenstone to have been forced up through the strata by 

 a subterranean fire, after these strata were consolidated. 

 And we might expect, also, that this convulsion would pro- 

 duce that wheeling of the strata observed in the central parts. 

 There is something peculiarly striking in this explanation, 

 and an inquiry arises, whether any corresponding facts oc- 

 cur in any other part of the coal formation. At mount To- 

 by, a few miles south of Gill and the highest point of the 

 coal formation, the strata dip to the east at an angle usually 

 less than 10°. And here the greenstone ridge on the west 

 is small, but the granite on the east, at no great distance, is 

 abundant. On the south east side of Mount Holyoke in 

 Belchertown and Granby, the strata dip to the south east, 

 near the mountain, at an angle not less than 45°, and the 

 greenstone ridge here is large. But the rocks that lie on 

 the back of Mount Tom, the highest point of greenstone 

 along the Connecticut, have a dip not generally larger than 

 20°. And the same remark will apply to many greenstone 

 ridges on the accompanying coal formation in Connecticut. 



