XIII.] GEOGNOSY OF THE APPALACHIANS. 241 



I. THE GEOGNOSY OF THE APPALACHIAN SYSTEM. 



The age and geological relations of the crystalline stratified 

 rocks of eastern North America have for a long time occupied 

 the attention of geologists. A section across northern New 

 York, from Ogdensburg on the St. Lawrence to Portland in 

 Maine, shows the existence of three distinct regions of unlike 

 crystalline schists. These are the Adirondacks to the west of 

 Lake Champlain, the Green Mountains of Vermont, and the 

 White Mountains of New Hampshire. The lithological and 

 mineralogical differences between the rocks of these three re- 

 gions are such as to have attracted the attention of some of the 

 earlier observers. Eaton, one of the founders of American 

 geology, at least as early as 1832 distinguished in his Geologi- 

 cal Text-Book (2d edition) between the gneiss of the Adiron- 

 dacks and that of the Green Mountains. Adopting the then 

 received divisions of primary, transition, secondary, and tertiary 

 rocks, he divided each of these series into three classes, which 

 he named carboniferous, quartzose, and calcareous ; meaning 

 by the first, schistose, or argillaceous strata such as, according to 

 him, might include carbonaceous matter. These three divisions, 

 in fact, corresponded to clay, sand, and lime-rocks, and were 

 supposed by him to be repeated in the same order in each 

 series. This was apparently the first recognition of that law of 

 cycles in sedimentation upon which I afterwards insisted in 

 1863.* Without, so far as I am aware, defining the relations 

 of the Adirondacks, he referred to the lowest or carboniferous 

 division of the primary series, the crystalline schists of the 

 Green Mountains, while the quartzites and marbles at their 

 western base were made the quartzose and calcareous divisions 

 of this primary series. The argillites and sandstones lying still 

 farther westward, but to the east of the Hudson River, were 

 regarded as the first and second divisions of the transition se- 



* Amer. Jour. Sci. (2), XXXV. 166. See, for an excellent presentation of 

 this subject, with references to its literature, a paper by Dr. Newberry in the 

 Proceedings of the American Association for the Advancement of Science for 

 1873, page 185. 



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