454 



SCIENTIFIC RECORD FOR 1883. 



from the valley of the Hudson to that of the Saint Lawrence, has been 

 known as the Hudson-River group, with the inclusion, however, in parts 

 of its distribution, as in Pennsylvania, of Lower Taconic slates, and 

 elsewhere of overlying Loraine shales. 



The appended table representing the nomenclature of Eaton, as pro- 

 posed by him fifty years since, with the modern names given to his divis- 

 ions, will serve to show the relations of the great groups mentioned to the 

 Silurian rocks above and the older crystalline strata beneath, and may 

 be read in connection with the classification of Eozoic and Paleozoic 

 rocks given in the report for 18S2. The Potsdam sandstone had not, in 

 the time of Eaton, been recognized as distinct from the Calciferous sand- 

 rocks. The student of American geology familiar with its history will 

 note that the great stratigraphical error of Mather and his followers 

 was in denying the distinctness of the First Gray wacke of Eaton, and 

 in asserting its identity with the Second Gray wacke, or, in other words, 

 in denying the existence of a Graywacke series beneath the horizon of 

 the Trenton limestone. There are, in fact, two such lower series, for the 

 great mass of sandstones and shales which make up the Primal of Rog- 

 ers, and, as they occur in Virginia, have been described above by Fon- 

 taine, occupy a position below the granular lime-rock of Eaton, and con- 

 stitute a Taconian Graywacke, not indicated in the table. 



Eaton's Nomenclature (1832). 



Later Names. 



4 

 



o 



SCorniferous Lime-rock . 

 Geodiferous Lime-rock 



2. Millstone-grit... ) gEC0ND 

 1. Graywacke-slate. $ Graywacke 



! Metalliferous Lime-rock 

 Sparry Lime-rock. Calciferous 

 Sand-rock 



(Millstone-grit....) FlRgT 

 '} Graywacke-slate .{Gbaywackb 



1. Argillite 



3. Granular Lime-rock 



2. Granular Quartz-rock 



1. Gneiss and other Crystalline 

 Rocks 



> Silurian. 



Upper Helderberg- Devonian. 



Niagara 



Oneida — Medina 

 Utica — Loraine . . . ^ 



? Ordovician. 

 Chazy— Trenton . . J P bffan.) am 



} Upper Taconic. 



(Quebec Group.) 



^Cambrian. 



(Middle and 

 Lower Cam- 

 brian.) 



> Lower Taconic. > Taconian. 



(Itacolumitic Group.) 



huronian. montalban. 

 Laurentian. Norian. Arvonian, 



