258 DR. THOMAS STERRY HUNT ON THE 
latter overlies the Trenton limestone ($ 7). If now, from any cause, this limestone should 
be absent, or should not appear in its usual character, it might very well happen that the 
Second should appear to succeed directly the First Graywacke. That such a condition of 
things occurs in the disturbed region east of the Hudson, had already been affirmed by 
Emmons in 1846. As I have elsewhere pointed out (Azoic Rocks, page 49), he then asserted 
the existence in this region of three distinct series of rocks: I. The Lower Taconic or 
Taconian limestones and slates. II. The First Graywacke, or Upper Taconic, resting in 
apparent unconformity upon the former, and itself partially eroded before the deposition of 
III ; which consists of shales and sandstones belonging to the upper portions of the Cham- ~ 
plain division or the Second Graywacke, and rests unconformably, in many localities east 
of the Hudson, both on I. and II. ; having itself been subsequently disturbed and eroded. 
§109. These observations accord with many others to show the existence of at least two 
important stratigraphical breaks, with unconformity, in this eastern region: the first 
between the Taconic and the First Graywacke, already pointed out by Haton, and the second 
at the summit of the same Graywacke series ; thereby dividing, in this eastern region, the 
Champlain division into two distinct periods, the second one of which began with the 
deposition of the Trenton, or rather, perhaps with that of the immediately subjacent 
Chazy limestone. 
The Laurentian regions of the Adirondacks and the Laurentides were not, at this early 
time, as has been so often said, the nucleus of a growing continent, but higher portions of 
a subsiding one, Upon its ancient gneiss we find reposing directly, in different localities, 
the Potsdam, the Calciferous, the Chazy, and the Trenton sub-divisions. The deposition of 
the Trenton marks a time of subsidence, during which, along the Laurentides, the sea 
extended far and wide to the northward, and the marine limestones of the Trenton, over- 
lapping the lower members of the Champlain division, were laid down in the regions to the 
north of Lake Ontario, and of the lower St. Lawrence, (as far eastward as the basin of Lake 
St. John on the Saguenay), directly on the submerged primary or eozoic rocks. 
After this period, and before the deposition of the succeeding mechanical sediments, 
extensive movements took place in the region of the Ottawa and Champlain valleys, and 
still farther south, which serve to throw light upon the problem before us. 
§110. A striking illustration of this disturbance is shown on the geological map of 
Canada, where, immediately south and east of the city of Ottawa, appears an outlier of 
Utica slate, overlaid by grey calcareous sandstone, holding the fossil remains of the Loraine, 
and associated with red slates ; the two possibly representing the Oneida and the Medina. 
This outlier, with a length of about twenty miles from east to west, reposes transgressively 
alike upon the Trenton, Chazy and Calciferous subdivisions. All three of these, with a 
slight eastward dip towards the centre of the Ottawa basin, appear successively, in passing 
from west to east along the southern border of this unconformably overlying area of newer 
strata, which are here preserved by having been let down along the north side of 
an east-and-west dislocation ; thus testifying to a former extension of the Second Gray- 
wacke over this area; where it lies unconformably, not only on the Calciferous Sand-rock, 
the representative of the First Graywacke, but on the Trenton limestone itself. For farther 
references to the details of this region, which was carefully mapped by Logan, see my 
Azoic Rocks, page 50. We have here, in the valley of the Ottawa, evidences of the same 
conditions as were described by Emmons in that of the Hudson; namely, the unconform- , 

