118 The Taconic Question Restated. [ Feb, 
vision, modified greatly by metamorphic agencies and by the 
intrusion of granitic and trappean aggregates.” The passage ~ 
between the unaltered and the altered rocks was supposed to 
offer a gradual transition, and it was asserted that “no well- 
marked line of distinction can be drawn, as they blend into each 
other by insensible degrees of difference,’ or what have since 
been called-successive “ grades of metamorphism.” These same 
- notions were soon afterwards adopted by Logan for the crystal- 
line rocks of the Atlantic belt in Canada, and for a time were 
extended by H. D. and W. B. Rogers to the gneisses and crystal- 
line schists of the White Mountains, 
§ 7. A similar view was also adopted for Pennsylvania by H. D. 
Rogers, then engaged in a geological survey of that State, who 
maintained with Mather that the Primitive Quartz-rock, the 
Primitive Lime-rock, and the Transition Argillite of Eaton, which 
are prolonged into Pennsylvania, were but the altered representa- 
tives of the Potsdam sandstone with the succeeding limestones 
and the Utica slate and Loraine shale of the Adirondack region. 
These silicious, calcareous, and argillaceous groups were named 
by him respectively the Primal, Auroral, and Matinal divisions 
of the palzozoic series, and were also called Nos. I., IL, and III. 
in his notation. ‘hese he supposed to appear in a more or less 
` metamorphosed and crystalline condition in the southeastern 
part of Pennsylvania; while farther westward in the State they 
occur in their unchanged fossiliferous condition, as in the Adiron- 
dack region, and are there conformably overlaid by the Oneida 
and Medina sandstones, which constitute together the Levant 
division, or No. IV. in the nomenclature of H. D. Rogers. 
§ 8. The First Graywacke of Eaton, which in Eastern New 
= York overlies the Transition Argillite, regarded by Mather as the 
altered representative of the Utica slate, was supposed by him to 
be the succeeding Loraine, Oneida, and Medina subdivisions. — 
He thus denied the distinctness of the great belt which Eaton 
had traced from Canada, through Vermont,-along the line be- 
tween Massachusetts and New York, and confounded it with the 
lithologically similar Second Graywacke. 
The areas of this First Graywacke, which in the southeastern 
part of Pennsylvania occur above the so-called “altered Auroral 
ae but below the horizon of the typical Levant or 
by H. D. Rogers to be a part 
