TACONIC QUESTION IN GEOLOGY. 267 
layers, which constitute the typical Chazy of the Ottawa basin.* The above facts with 
regard to the Chazy are additional evidences of the period of disturbance, which, as already 
set forth, marked the close of the Cambrian period, and brought im the Ordovician. The 
continental movements of that time, while they plicated and uplifted the previously 
deposited fossiliferous strata along the southeastern border of the Cambrian area, caused 
elsewhere a subsidence which allowed the Ordovician sea to spread far and wide to the 
north, depositing its nearly pure limestones, with a thickness of 600 feet or more, along 
the St. Lawrence valley, not only over the Cambrian beds, but over the eozoic land. 
§ 131. To the south and east, however, the uplifted and eroded Cambrian strata, with 
their adjacent eozoic rocks, the Taconian included, formed the eastern shores of the Ordo- 
vician sea, approaching which, as we have already seen, (§ 111) the massive limestones of 
that period become thinner and disappear; being apparently replaced by the black shaly 
beds, which, at various points, are found lying among the older rocks. How far the sub- 
sequent movement—which, as has been shown, disturbed and eroded the Trenton lime- 
stone in the Ottawa valley before the deposition of the Loraine shale (§ 110)—was felt in 
this eastern region is uncertain. It is also a question how far the higher strata, known as 
the Oneida sandstone, were laid down in this region over the Loraine shale. This is 
found preserved from denudation in regions to the east of Lake Champlain, along the lines 
of dislocation which have brought up on its eastern side the underlying Cambrian strata ; 
and it is not improbable that portions of the upper sandstone of the Second Gray wacke 
may, as some have supposed, there be found in the vicinity of the First Gray wacke. 
§ 132. We have already noticed the subsequent invasion of the Silurian sea, depositing 
its limestones over the lower levels from central New York northward and eastward as 
far as Gaspé and Newfoundland. Thus it happens that we find portions of these limestones 
overlying alike Ordovician, Cambrian, Taconian, and still older strata, and involved with 
these by subsequent movements of the strata. As a result of these geological accidents, 
successive observers have been led into many errors. Thus, the Taconian marbles have, 
within the last generation, been, by different geologists, declared to be of Cambrian, of 
Ordovician, of Silurian, and even of Devonian age; while similar views have been main- 
tained with regard to the geological horizon of the still older crystalline schists of the 
region, of which we have already given examples ($121, 123). 
§ 133. The statement which has been made, and often repeated, that in Cambrian and 
Ordovician times the rocks of the Green Mountains were laid down as sediments beneath 
the sea, and that at the close of this latter period, these were hardened, crystallized and 
uplifted as a mountain-range, is seen, from what has been set forth, to be a fiction based 
upon the gratuitous hypothesis, first clearly formulated by Mather, and repeated by his 
successors, (including, during many years, the present writer), that the rocks of this monn- 
tain-range are altered paleozoic strata. Of this, there is no evidence, while, on the con- 
trary, the relations of the paleozoic strata to these crystalline rocks throughout the Atlan- 
tic belt, and the presence of fragments of these in the paleozoic conglomerates, demonstrate 
their greater antiquity. The same considerations apply, « fortiori, to the similar hypothesis 
of the crystallization, folding and uplifting of Silurian and Devonian rocks at the close of 
paleozoic time, to form the White Mountain range. 

* Hunt, Azoic Rocks, pp. 124, 139. 
