Marcu 15, 1901.] 
mountain axis, previously in existence, was 
evidently greatly increased in elevation. 
The Laramide geosyncline has already 
been particularly referred to and allusion 
has been made to the now well recognized 
fact that by such zones of continued sub- 
sidence and deposition the lines of most 
mountain systems have been determined. 
To the Laramide geosyncline here, the 
mountains of the Archean axis—the Gold 
ranges—stood in much the same relation as 
the Archean western border of the Wasatch 
to the Laramide geosyncline in Utah (as 
described by Dana), but on a larger scale. 
On the other or western side of this axis, 
as already noted, I am now led to regard 
the zone of country extending to the Van- 
couver range as asecond and wider geosyn- 
cline with a breadth of about 200 miles, in 
whicha thicknessof deposits, perhapsgreater 
than that of the Laramide, but in the main 
composed of volcanic ejectamenta, had by 
this time been accumulated. The volume 
of the Carboniferous and Triassic rocks 
alone must have exceeded 20,000 feet. It 
is probable that to this may be added a 
great thickness of older rocks,* for the cir- 
cumstance that volcanic action was so per- 
sistent here and the amount of extravasa- 
tion resulting from it was so enormous, 
implies a recognition of the fact that, along 
this zone (not far from the edge of the conti- 
nental plateau) the isogeotherms, with what 
we may call the plane of granitic fusion, had 
crept up to a position abnormally near the 
surface. It is to this probably that we 
may attribute the apparent absence of Ar- 
chean rocks in the Coast ranges, or at least 
the impossibility of defining any rocks of 
that period there, for these, together, no 
doubt, with great volumes of later deposits, 
*Several thousand feet of Cretaceous rocks must 
also be added to this thickness near the line of she 
present Coast ranges, and the total thickness of de- 
posits in the center of this geosyncline must probably 
have exceeded 40,000 feet. 
SCIENCE. 
405 
may be assumed to have become merged in 
the rising granitic magma, on which strata 
of Triassic age are now often found lying 
directly, arrested in the very process of 
absorption.* 
When the Laramide revolution occurred, 
by reason of the increasing tangential pres- 
sure from the Pacific basin and the growing 
failure of resistance of the two great geosyn- 
clines of this part of the Cordillera, the 
Laramide range was produced by the fold- 
ing and fracture of a very thick mass of 
beds, of which the erystalline base has not 
yet been revealed by denudation, while in 
the western trough an eversion of the axis 
of settlement seems to have occurred, re- 
sulting in the appearance of a granitic 
bathylite of nearly a thousand miles in 
length, from which the comparatively thin 
covering of unabsorbed beds was soon after- 
ward almost completely stripped away by 
ensuing processes of waste. 
This last great epoch of mountain mak- 
ing doubtless left the surface of the Cordil- 
leran belt generally with a very strong 
and newly made relief, which before the 
middle of the Tertiary period is found to 
have become greatly modified by denuda- 
tion. Chiefly because no deposits referable 
to the Eocene or earliest Tertiary have been 
found in this part of the Cordillera, it is 
assumed with probability that this was a 
time of denudation. It is further indicated 
that it was a time of stability in elevation 
by the fact that the prolonged wearing 
down resulted, in the interior zone of the 
Cordillera, in the production of a great 
peneplain, the base-level of which shows 
that the area affected stood for a very 
long time 2,000 or 3,000 feet lower in re- 
lation to the sea than it now does. If, 
however, the Puget beds of the coast are 
correctly referred to the Hocene, it follows 
that the coast region was ati the same period 
*Annual Report, Geol. Surv. Can., Vol. II. (N.S.), 
1886, p. 11 B et seq- 
