186 CRUISE OF THE NEPTUNE 
allow the sedimentary deposits to preserve their original unal- 
tered conditions. All the above rocks are grouped in the 
Archaean, and further and closer examination will probably 
show that it contains all the members of the laurentian and 
Huronian found in the more southern Archaean regions of 
Canada. 
Except in the northern part of Ellesmere, there is a consider- 
able time-break in the geological sequence in the northeast 
between the Archaean rocks and the Cambro-Silurian strata 
which rest unconformably upon them. Schei found at Bache 
peninsula, on the eastern side of Ellesmere, a series of stratified 
sedimentary rocks resting upon the northern flank of the 
Archaean and containing fossils of Cambrian age. These de- 
posits have a thickness of nearly 1,500 feet, and are overlaid by 
limestones containing Cambro-Silurian fossils. 
The Archaean rocks at the time of deposition of the lower 
beds of the Cambro-Silurian limestones appear to have extended 
southward from the vicinity of Bache peninsula in a gradually 
widening ridge along the western side of Baffin bay and Davis 
strait. In this manner they attained a width of seventy miles 
on the southern side of north devon, and occupied the entire 
southern shore of Baffin island, being separated from the great 
area of Labrador by the depression of Hudson strait, which 
probably existed at that early period. Islands of Archaean rocks 
may also have risen above the surface of the Cambro-Silurian 
sea in the present island of North Somerset and on Melville 
and Boothia peninsulas, as well as on other portions of the 
northern coasts of the mainland, to the west of Hudson bay. 
The western Cambro-Silurian sea filled the present depres- 
sion of Hudson bay, and extended far to the south and westward 
of its present limits, outliers of limestone containing fossils of 
this age, and very similar in mineral character, being found in 
the valleys of the great lakes of Manitoba. From Manitoba 
these rocks have been traced southward into the United States, 
