OBSERVATIONS ON METAMORPHISM. 81 



OBSERVATIONS ON METAMORPHISM. 



A few remarks seem to be called for in this place, in answer to the views of Prof. 

 Rogers and others, who maintain the doctrine that the Stockbridge limestone is a meta- 

 morphic rock. I will first select a passage from his late Address before the Association of 

 American Geologists and Naturalists. I would premise, however, that I protest against 

 opinions on important geological points, unless they are based upon some fact, and those 

 facts are such that others can see and draw their inferences from localities which they can 

 examine. The passage referred to reads thus : 



" The granular Berkshire marble (Stockbridge limestone) was identified with the blue 

 " limestone of the Hudson valley, but metamorphosed by heat ; and the associated mica- 

 " ceous schists were referred, in the language of the communication, to the slates of the 

 " lowest formation of the Appalachian system, while the semivitrified quartz of the western 

 " part of the Hoosic mountain was stated to be nothing else than white sandstone (Potsdam 

 " sandstone) of the same series slightly altered."* 



It would appear from this passage, to one unacquainted with facts, that something had 

 been shown or demonstrated, because the words used, " identified with" require the 

 highest kind of proof, and imply the nearest relationship ; but after all, nothing has 

 appeared on the whole face of the subject, but opinion, mere opinion. 



I have introduced this passage from the Address, not for the purpose of finding fault, 

 but for showing what Prof. Rogers's views really are, that there may be no misunderstand- 

 ing in relation to this interesting subject ; and I cannot but hope that my friend, in his 

 communications in future, will avoid the words " identified with," when he speaks of the 

 Berkshire marble. 



One of my arguments for the non-identity of the marbles and slates, etc. of the Taconic 

 system, was drawn from the order of succession of the members of the system, an order 

 essentially different from that of the Champlain or lower division of the New- York series. 

 This argument I still maintain, and challenge any geologist to reconcile the order of one 

 system with the other. While Prof. R. admits that this is true apparently, I maintain 

 that it is really and actually true ; and to satisfy an impartial mind that it is so, it would 

 seem that it is only necessary to enumerate the order of the rocks, and compare them 

 respectively with each other. Compare, for example, the marbles of Berkshire with the 

 blue limestones of the Champlain group .- the former are in the midst of an immense slate 

 formation ; the latter, when all members are present, rest upon the Potsdam sandstone. 



But it is unnecessary to dwell upon facts of this kind, when there is a conclusive one ; 

 one sufficient to silence all others, namely, direct superposition of the blue limestones 

 upon the taconic slates, as I have exhibited in my actual sections along the Champlain 

 and Hudson valleys. 



'American Journal of Science and Arts, p. 151. 

 [Agricultural Report.] 11 



