TACONIC QUESTION IN GEOLOGY. 263 
have been known both as the Hudson-River group and the Quebee group. This statement 
we have justified in the preceding pages, and are now prepared to state succinctly what 
has been the precise meaning attached to these two terms, which have been so conspicuous 
in the history of American geology. The Hudson-River group, by the admission of 
Vanuxem, who first proposed it, was a composite one, devised to include two, if not three 
divisions of strata, in part of disputed age, but at the same time embracing in its upper 
portion the Loraine shales. As this was the only part of the group of which the fauna 
was known, the name of Loraine shales, in paleontological language, soon came to be 
regarded as the equivalent of Hudson-River group; and thus the fact of its heterogen- 
eous character, clearly stated by Vanuxem, was lost sight of. Meanwhile, the name of 
Hudson-River group was applied stratigraphically to the whole of the First Graywacke 
of Eaton, with its succeeding Sparry Lime-rock. This is seen from the language of James 
Hall, who, in 1857, wrote of the graptolites found in slates with the limestone of Pointe 
Levis, at that time assigned by Logan to this horizon, that they are met with in “that part 
of the Hudson-River group which is sometimes designated as Haton’s Sparry limestone,— 
being near the summit of the group.” * 
§ 121. The Red Sand-rock of Vermont was also, at the same time, regarded as either 
forming a part of the same group, or as closely related to it. Thus Hall, in describing in 
1859, the trilobites of the genus Olenellus, found in shales intercalated in the Red Sand- 
rock in Georgia, Vermont, which he then referred to this horizon, wrote, “I have the testi- 
mony of Sir William Logan, that the shales of this locality are iu the upper part of the 
Hudson-River group, or forming a part of a series of strata which he is inclined to rank as 
a distinct group, above the Hudson-River group proper.” f 
We have farther to mention in this connection, the notion of Mather, who supposed 
that the crystalline rocks of western New England, including the crystalline limestones, 
“and probably the associated micaceous gneiss, mica-slate, hornblende-slate and horn- 
blende-rocks : . . are nothing more than the rocks of the Champlain division greatly 
modified by metamorphic agency.” This view was adopted by Logan, aud the similar 
crystalline rocks of the Green-Mountain belt in Canada were described as belonging to 
the altered Hudson-River group. 
§ 122. The Quebec group, which, in 1861, succeeded to the Hudson-River group, inher- 
ited its traditions, with a few exceptions. Its horizon being now changed from above 
to below the Trenton limestone, it could, of course, no longer include within its limits the 
fauna of the Loraine shales, belonging to the Second Graywacke. The greater antiquity of 
the fauna of the Red Sandrock of Vermont having in the meantime been recognized, these 
rocks were assigned, under the name of Potsdam, to a position beneath the new Quebec 
group. To this lower horizon, moreover, Logan, at the same time, referred certain black 
slates in Canada, which, though apparently underlying the Graywacke series, have since 
been found of Ordovician age ($ 119). 
The Quebec group, as at first defined, was nothing more nor less than the First 
Graywacke of Eaton, with its overlying Sparry Lime-rock; which is really an upper 

* Report Geol. Survey of Canada, 1857, page 117. 
+ Twelfth An. Rep. Regents of the University of New York, 1859; cited by Barrande, American Jour. Science 
(2) xxxi., page 213. 
