306 MORLEY E. WILSON 
north of Lake Superior are the same. (3) From (1) and (2) it is 
inferred that the pre-Huronian erosion plane was also originally 
continuous with the pre-Animikie or Eparchaean erosion plane, 
and that the rocks classed as Lower-Middle Huronian in the 
region north of Lake Superior are therefore a part of the basement 
complex and in reality pre-Huronian in age. (4) If the rocks 
classed as Lower and Middle Huronian in the region south of Lake 
Superior have been correctly correlated with the original Huronian, 
then these series must also be younger than the Lower-Middle 
Huronian of the region north of Lake Superior; (5) A direct com- 
parison of the Lower-Middle Huronian of the region north of Lake 
Superior with the Lower and Middle Huronian occurring to the 
south of Lake Superior shows that the correlation of these series is 
based on evidence from which an alternative inference conforming 
to the conclusion cited in (3) may be drawn. 
With the progress of geological investigation in the pre- 
Cambrian terranes of the Canadian oldland, new facts are con- 
stantly being added to our knowledge of their stratigraphy, and 
from the evidence now available it can be reasonably inferred that 
the pre-Cambrian rocks throughout the whole of the Lake Superior 
region and eastward through northern Ontario and western Quebec, 
fall naturally into two great divisions, an older complex and a 
group of younger rocks, which differ from the complex in that 
they generally contain a much larger proportion of sediments, are 
generally much less highly folded and metamorphosed, and as far 
as geological investigation has shown, are nowhere intruded by 
batholiths of granite or gneiss. This younger group of rocks 
includes (1) the Cobalt series in the Timiskaming region, (2) the 
Animikie and Keweenawan series in the region north of Lake 
Superior, (3) the original Huronian series on the north shore of 
Lake Huron, and (4) the rocks known as Lower Huronian, Middle 
Huronian, Upper Huronian and Keweenawan in the region south 
of Lake Superior. This conception of the stratigraphical relation- 
ships of these various younger pre-Cambrian series involves no 
unusual phenomena, for just as in later geological periods Cre- 
taceous, Silurian, and other sediments of different ages were 
deposited on the surface of the same basal complex, so in Huronian 
