STRUCTURAL RELATIONS OF PRE-CAMBRIAN AND PALAEOZOIC. 19 
hills. The two conspicuous tongues of Archaean which indent 
the Ordovician east and west of Jacques Cartier river are very 
much lower than the main front of the Laurentian plateau and 
probably represent hills in the old Pre- Cambrian surface such as 
have been described in the first part of this paper. Similar 
granite hills which lie south of the line of fault are locally con- 
spicuous in the Ottawa River valley above Quyon. The western 
extent of the fault is unknown. North and northwest of Chi- 
chester P.O. f which is the most westerly point visited, the Lau- 
rentian plateau terminates in a scarp or line of hills which rises 
with about the same abruptness and relative elevation above 
the country to the south as in the lower Ottawa valley. 
FORMER EXTENT OF THE PALAEOZOIC. 
The interpretation of the relationship of the Palaeozoic 
plain to the Laurentian plateau which has been set forth above 
is one which requires a very material alteration of the current 
view of the former extent of some of the Palaeozoic rocks in the 
extensive region north of the St. Lawrence and Ottawa rivers. 
The great V-shaped area of Archaean rocks, which embraces the 
Hudson Bay depression and extends southward from the Arctic 
coast on the west and from northern Labrador on the east to 
the Ottawa and St. Lawrence rivers and the upper Great Lakes, 
has long been considered to represent the approximate outlines 
of a Pre-Cambrian continent, which persisted through Palaeozoic 
time. Dana, who appears to have been the original exponent 
of this conception of the Pre-Cambrian continent, gives his reason 
for believing that the lands of this area were above sea-level, 
in the following words: “They are concluded to have been thus 
dry because no marine beds cover them, while on either border 
marine beds (Silurian and later) commence and spread widely 
over the most of the continent .” 1 In view of the extensive 
denudation which most lands of the present are now known to 
have suffered, the mere absence of a formation or formations 
cannot be admitted as good evidence that they may not have 
been present at some earlier period. With few exceptions, 
1 Dana M J. D., Manual of Geol., Rev. Ed., 1868, p. 136. 
