[BLLS & BARLOW] PROPOSED OTTAWA CANAL 177 
the stratigraphical sequence can be well observed at various places. 
There does not appear to be any defined break throughout the whole 
series, though the estimate of their total thickness is affected to some 
extent by the presence of local faults. The basal beds of the lowest or 
Potsdam sandstone are in places made up of the débris from the Lauren- 
tian gneiss and limestone, while in other places the sandstones are pene- 
trated by dykes of granite, which were formerly considered as integral 
portions of the Archean rocks. The descriptions of these various divi- 
sions of sedimentary rocks are given fully in the earlier reports of the 
Geological Survey of Canada, and need not be here repeated.’ 
At several places along the Mattawa and Lake Nipissing portions of 
the route certain Paleozoic strata are also seen resting in almost horizon- 
tal beds on the hummocky surface of the pre-existing Archean. <A few 
of these outliers may be noticed at low water dipping from the edge of the 
gneiss, and forming a portion of the bed of the Ottawa River a few miles 
below Mattawa. The rock is a light gray arenaceous limestone, and the 
study of the few fossil remains which were obtained points to their being 
of Black River age. Strata representing the same period, and containing 
much more numerous and better preserved fossil remains, were also noticed 
on several of the Manitou Islands, in Lake Nipissing. The thickest sec- 
tion of these rocks appears to be near the southwest end of McDonald 
Island, the second in size of the Manitou group, where these rocks have 
a thickness of about thirty feet. The lowest bed exposed on these islands 
appears to be a coarse arkose made up of angular or subangular frag- 
ments of the subjacent gneiss, cemented together by a coarse sandstone or 
grit. This has no great thickness, and graduates quickly upward into a 
sandstone holding corals and fragments of what must have been in some 
cases very large orthoceratites. This in turn gives place to a gray lime- 
stone, which continues to the top of the series. Near the southwest end 
of Iron Island beds of a coarse sandstone or grit rest unconformably upon 
the gneiss, dipping at a very low angle to the west. 
The Archean rocks which form the great bulk of the strata through- 
out the entire area under consideration have been studied by various 
observers for three-quarters of a century. As early as 1821 Bigsby 
described the rocks north of Lake Huron as granite, gneiss, trap, etc., 
all of which were at that time assigned to the primitive formation. 
In 1827 the same observer also described similar rocks along the north 
side of the St. Lawrence in the vicinity of Quebec. Among subsequent 
early writers on these rocks were Sir Wm. Logan, Murray, Bayfield, 
Emmons and Hunt, while in more recent years Macfarlane, Selwyn, Ven- 
nor, Bell, Barlow, Lawson and others have added many important facts 
relating to their distribution, origin and general structure. The terms 
Laurentian and Huronian, given by Logan and Murray in 1852-54 for 
a — "ee ee 

1 Geological Survey Report, 1845, W. E. Logan; 1851, A. Murray. 
Sec. IV., 1895. 12. 
