TACONIC QUESTION IN GEOLOGY. 257 
Pointe Levis, to which the name of the Levis division was given, at the base of the series ; 
an intermediate portion receiving the name of the Lauzon division. The real order, 
however, as described both by Emmons in Vermont, and by Murray in Newfoundland was 
the reverse of this ; and the Sillery sandstone, in truth, the oldest member of the series 
here displayed. Logan, as we have seen, maintained that the typical section of southeast- 
ward-dipping strata at Quebec, estimated by him to measure 7,000 feet, was the southeast 
side of an eroded anticlinal, and represented the rocks of his Quebec group in their natural 
order; the Levis division at the base and the Sillery at the summit. I have long since 
endeavored to show, alike on structural and on paleontological grounds, that this view is 
erroneous, and that we have here an inverted succession. The true position of the Nillery 
is at the base of the series, and we have here exposed the eroded surface of the northwest 
side of an overturned anticlinal, by which the Sillery sandstone is made to overlie the 
younger members of the Graywacke series.* The succession is thus brought into harmony 
with that determined by Eaton, and by Emmons, in many sections farther south. This 
series, which had been previously called the Hudson-River group, was now by Logan, and 
the Canada geological survey, named the Quebec group, and was described as a great 
development of strata between the Trenton limestone and the Potsdam sandstone ; which 
latter, Logan conceived to be represented by certain black shales, that in several localities 
appear to pass between the Levis division. The rocks of this series were now, by Logan 
and his assistants, traced down the St. Lawrence to Newfoundland, on the one hand, and 
to the valley of Lake Champlain on the other; where, however, the Red Sand-rock was 
supposed to represent the Potsdam. The history of these investigations I have elsewhere 
set forth in Azoic Rocks, pp. 81-125. 
It should here be said that this view, which made the Sillery the youngest member 
of the series was, in 1862 questioned by Billings, who inclined, with the writer, to place it 
at the base of the series ; while its evident basal position in Newfoundland led Logan also 
to express doubts, and to look upon the order assumed by him as simply provisional. 
$ 107. It remained, however, to determine how far this identification with the First 
Graywacke applied to the rocks farther south, in the valley of the Hudson, to which the 
name of the Hudson-River group had first been given; and which had been declared, alike 
by Eaton, Emmons and Mather, to be geographically and stratigraphically identical with 
the similar rocks in Vermont and in Canada. These rocks in the Hudson valley had been 
by Mather assigned to the horizon of the Second Graywacke, and from the occurrence in 
portions of them of the fauna of the Loraine or Pnlaski shales, he, with Vanuxem had, as 
we have seen, been led to employ the names of Hudson slates and Hudson-River group as 
synonymous with that of Loraine shales. The opposition between the view of Mather, on 
the one hand, and that of Emmons, now adopted by Logau, on the other, as to the horizon 
of the so-called Hudson-River group, was thus radical and complete. 
§ 108. A question here arises whether it might not be possible to reconcile these two 
seemingly contradictory views by showing the belt of disturbed strata in question to 
include both the First and the Second Graywacke. These, as we have seen, were declared 
to resemble each other so closely as to be scarcely distinguishable save by the fact that the 

* Harper’s Annual Record for 1876, page xcviii., and for 1877, page 167. 
+ Billings; Paleozoic Fossils, 1865, p. 69, and Logan, Geology of Canada, 1863, p. 880. 
Sec. IV., 1883. 33. 
