402 
have often been affected in it; nor has any 
series yet been defined that appears here 
to bridge the gap between the Archean and 
the strata that may with propriety be at- 
tached to the Cambrian. 
_In the earlier series of deposits assigned 
to the Cambrian, we discover evidence of a 
more or less continuous land area occupy- 
ing the position of the Gold ranges and 
their northern representatives, and aligned 
in a generally northwesterly direction. 
The Archean rocks were here undergoing 
denudation, and it is along this axis that 
they are still chiefly exposed, for although 
they may at more than one time have been 
entirely buried beneath accumulating strata, 
they have been brought to the surface 
again by succeeding uplifts and renewed 
denudation. We find here, in effect, an 
Archean axis or geanticline that consti- 
tutes, I believe, the key to the structure of 
this entire region of the Cordillera. To the 
east of it lies the Laramide geosyncline 
(with the conception of which Dana has 
familiarized us) on the west another and 
wider geosyncline, to which more detailed 
allusion will be made later. 
Conglomerates in the Bow River series 
indicate sea margins on the east side of 
this old Jand, but these are not a marked 
feature in the Nisconlith, or corresponding 
series on its western side. . Fossils have so 
far been discovered only in the upper part 
of the Bow River series, but the prevalence 
of carbonaceous and calcareous material 
(particularly in the Nisconlith) appears to 
indicate the abundant presence of organ- 
isms of some kind at this time. 
Although no evidence has been found of 
any great physical break, the conditions 
indicated by the upper half of the Cambrian 
are very different from those of the lower. 
Volcanic materials, due to local eruptions, 
were accumulated in great mass in the 
region bordering on the Archean axis to 
the west, while on the east materials of 
SCIENCE. 
[N.S. Von. XIII. No. 324. 
this kind appear to be mingled with the 
preponderant shore deposits of that side of 
the Archean land, and to enter sparingly 
into the composition of the generally calca- 
reous sediments lying still farther eastward. 
Where these sediments now appear in the 
eastern part of the Laramide range they 
are chiefly limestone, indicating marine 
deposition at a considerable distance from 
any land. 
The history of the Ordovician, Silurian 
and Devonian times is very imperfectly 
known. Marine conditions still prevailed 
to the eastward of the Archean axis and 
were probably continuous there, but our 
knowledge of the region to the west, while 
as yet almost entirely negative in its char- 
acter, is not sufficiently complete to enable 
us to assume the existence of any extensive 
land area in that quarter. In the Devonian 
the sea is known to have covered a great 
area in the interior of the continent, ex- 
tending far to the north in the Mackenzie 
basin, and it appears probable that con- 
siderable portions of the western part of 
the Cordilleran region were also submerged, 
particularly to the north. 
About the beginning of the Carboniferous 
period and thence onward the evidence be- 
comes much more satisfactory and complete. 
In the earlier part of the Carboniferous, 
marine sediments, chiefly limestones, were 
laid down everywhere to the east of the 
Archean axis, while to the west of that axis 
(which was probably in large part itself 
submerged) ordinary clastic deposits, min- 
gled with contemporaneous volcanic ma- 
terials, were formed, tranquil epochs being 
marked by the intercalation of occasional 
limestone beds. It is not clearly appar- 
ent from what land the clastic materials 
were derived, but the area of vulcanism 
at this time was very great, covering 
the entire western part of British Colum- 
bia to the edge of the continental plateau 
and, as now known, extending northwest- 
