TACONIC QUESTION IN GEOLOGY. 255 
have, according to Emmons, an apparent thickness of not less than 25,000 feet; a volume 
probably due to repetitions from numerous parallel dislocations, with upthrows on the 
east side ; as a result of which the succession already described is apparently inverted, so 
that the black slates of the western part of the section seem to pass beneath all the other 
members, and the green sandstones of the eastern part appear to overlie them all. 
$101. This condition of things, so far from being exceptional, is very frequent along 
the eastern base cf the Atlantic belt, from the Gulf of St. Lawrence to Alabama, and is 
apparently general in similar disturbed regions. Emmons has described this with_detail, 
_and noted the parallel uplifts, increasing in vertical extent as we approach the mountain- 
chain of older rocks. I have discussed this matter, with many illustrations, in my report 
on Azoic Rocks, pages 54, 55. 
It is there shown that along the whole eastern side of the great Appalachian valley 
the newer rocks are found dipping to the eastward, towards the older rocks, and sometimes 
even beneath them. Thus, the Cambrian Graywacke appears to pass beneath the crystal- 
line rocks of the Highlands and of Newfoundland ; the Ordovician beds beneath this First 
Graywacke, and farther southward, in Virginia, the Carboniferous rocks beneath the older 
paleozoic. These relations result from dislocations, with uplifts on the eastern side, often 
connected with inverted folds. 
§ 102. While the green sandstones in New England, according to Emmons, constitute, 
along its eastern border, the base of the series, there appears farther west in the valley, along 
the eastern shore of Lake Champlain, another mass of strata, the so-called Red Sand-rock of 
Vermont, which, towards the summit, becomes a reddish limestone or marble. These strata, 
which have yielded a Lower Cambrian fauna, were by C. B. Adams referred to the horizon 
of the Medina and Clinton ; and by Logan in 1859, were said to belong to the summit of the 
Hudson-River group, or possibly to a still higher horizon. These rocks, were, however, in 
1855, assigned by Emmons to a position still lower than the green sandstones, and were 
supposed to represent the Potsdam of the Champlain division; while the remaining portion 
of the Upper Taconic was regarded as the equivalent to the Calciferous Sand-rock. The Red 
Sand-rock in western Vermont is brought up by a dislocation, and the higher members of 
the Champlain division, appear to pass conformably beneath it to the eastward. The same 
conditions are met with in the Lower Cambrian beds at Troy, New York, studied by Ford ; 
which there overlie the Loraine shales, and were by Billings assigned to the same geolo- 
gical horizon as the Red Sand-rock, with the name of Lower Potsdam. The outcrop of 
these strata in Georgia, Vermont, according, to Logan, exposes a thickness of not less than 
2,200 feet ; in the lower part of which are included the argillaceous beds holding Olenellus, 
with Conocephalites and Obollela. 
VI—THE UPPER TACONIC IN CANADA. 
§ 103. Weare now prepared to notice the studies of this Gray wacke-belt in its extension 
through Canada, from Vermont to the St. Lawrence. Logan, who, in 1845, published 
a preliminary account of the geology of Canada, expressed therein the opinion that the 
contorted strata at, and near the city of Quebec, which are those of the belt in question, 
were older than the adjacent horizontal (Trenton) limestones ; but in a foot-note referred 
favorably to the view (which had been maintained byjEmmons in 1842), that they were 
