Geology, <f/-c. of the Connecticut, 29 



Gneiss. 



The more I examine the rocks in New-England, the bet- 

 ter convinced I am that the extent of this rock in this re- 

 gion, has been overrated by geologists. The truth is, that 

 almost in every place which I have examined, mica slate al- 

 ternates with gneiss, or overlies it, so as to occupy nearly, 

 sometimes more than half the surface. Hornblende slate 

 and granite, also occur in the same series. In passing from 

 Northaiaipton to Bosto-*, I have never found any gneiss east 

 of Worcester ; although in going from Providence to Hart- 

 ford, this stratum occurs only twelve miles from the former 

 place and continues with alternations of mica slate, &;c. 

 to within a few miles of 'he latter place. 



I cannot avoid remarking here, that wherever I have 

 seien beds and veins of granite in gneiss and mica slate, I 

 have usually found the strata much distorted and deranged 

 in the vicinty ; and rice versa, where derangement of the 

 slate appeared, I have generally been able to discover veins 

 or beds of granite. And wherever granite veins exist, gra- 

 nite beds are not usually far off. I might say more on this 

 subject : But it has only recently attracted my particular 

 attention, therefore I desist. I am satisfied, however, that 

 many of the phenomena of Glen Tilt are repeated in New- 

 England. 



Greenstone — primitive-r— transition and secondary. 



The second supposed distinction between the primitive and 

 secondary greenstone of the Connecticut is very imper- 

 fectly stated page 32 vol. 6. The mere fact that the primi- 

 tive greenstone forms beds in other rocks does not distin- 

 guish it from secondary greenstone ; since this occurs in the 

 same situation. But the former, at the sides of the bed, 

 passes by imperceptible gradations into other rocks, such 

 as greenstone slate, chlorite slate, &ec. thus excluding the 

 idea that it could have been forced in between the strata of 

 other rocks after their consolidation : whereas the latter 

 rock is distinctly characterized to the very line of junction 

 with the sandstones and puddingstones, unless there be a 

 slight chemical change a few inches on either side of thi^hne, 

 as if by heat. 



