354 Correspondence. 
proposed . The talcose rocks are, however, clearly dilf erent from those 
of the gneiss system, or those east of the Iloosick mountains, and the 
Mica slate may come up among the Taghkanic rocks and yet on a careful 
observation be foun^^ to be distinct from them. We believe this will be 
found to be the fact. On the whole in regard to those rocks we have de- 
nominated 'Taghkanic,' we believe they ought to be separated from those 
on the east, being as a whole, clearly distinct from them." 
7\ibuhir view of the Hocks of New York, urrauged in Systems and Groups. 
I. POST-TERTIAUY. 
Alluvial, Diluvial, Clays and sauds of the Post-tertiary- 
II. Old Red System. 
Old red sandstone. 
III. N. Y. TKANsmoN System. 
Erie Group. 
Chemung sandstones and flags, Ludlowville shales. 
Heldcrberg Series. 
Helderberg limestones, Schoharie grit, brown argillaceous sandstone, enerinallime 
stone, Oriskany sandstone, green shaly limestone, Pentamerus limestone. 
Ontario Group. 
Onondaga salt and gypseous rocks, limestone and green shales, argillaceous iron 
ore, soft red, green and variegated sandstones, or Medina sandstone. 
Cbaraplain Group. 
Gray sandstone and bed of conglomerate, Lorraine shales and roofing slates, Utica 
slate, Trenton limestone, Birdseye limestone, Chazy limest me, Calciferons sand- 
rock, Potsdam sandstone. 
IV. Taghkanic System, (Quartzite.j 
Light green slates sometime* dark and plumbaginous (middle Cambrian, Walcott.) 
Gray and clouded limestones, (Hudson River, etc., Walcott.) Brown sandstones, 
(Cambrian, Walcott.) 
V. Gneiss System. 
Gneiss, Hornblende and Mica slate, Talcose slate and steatite. 
VI. Sdpekincumbent Rocks. 
Greenstone trap— porphyry. 
VII. L'XSTRATIFIED RoCKS. 
Granite, Hypersthene rock, prim.xry limestone, .serpentine, rons,sel;erite, magnetic 
iron ore. 
Dr. Emmons remarks,(^4rti Quart. Jour. Agl. (tad Sci. y6'^.,iv,l846 p. 203.) 
that the first hints published in regard to the Taconic system appeared in 
DisturnelVs State Register, for which he wrote a brief article on the 
geology of the state of New York. He states, "In making up our notes 
for this object we found it necessary to fix upon some general subdivision 
of tlie rocks belonging to the state. We drew up an abstract of the plan 
and submitted it to the criticism of the liev. Prof. Dewey of Rochester 
* * * Prof. Dewey approved of the division proposed in the main. 
It resulted in separating the rocks in the vicinity of the Taconic ran ge, 
both from the Primary and the New York transition, as we then called 
them." 
The subdivisions then proposed in Dlsturiieirs State Register, and which 
were adopted in the report of the state geologists (Geol. N Y., Part ii, 
comprising the survey of the second Geol. District, by Ebenezer "Emmons 
Albany 1843, published May 3G, 1843) were (1) Primary, (3) Taconic, (3) 
