's Nest Trough, being ninety-five miles long.

But we ought to take a nearer view of these wonderful conditions. A
convenient point of approach will be just east of Banff, Alberta, near
Kananaskis Station, where the Fairholme Mountain has been described by
R.G. McConnell of the Canadian Survey. The latter remarks with amazement
on the perfectly natural appearance of these Algonkian limestones
resting in seeming conformability on Cretaceous shales, and says that
the line of separation between them, called in the theory the "thrust
plane," resembles in all respects an ordinary stratification plane. I
quote his language:

"The angle of inclination of its plane to the horizon is _very low_, and
in consequence of this its outcrop follows a very sinuous line along the
base of the mountains, and _acts exactly like the line of contact of two
nearly horizontal formations_.

"The best places for examining this fault are at the gaps of the Bow and
of the south fork of Ghost River.... The fault plane here is nearly
horizontal, and the two formations, viewed from the valley, _appear to
succeed one another conformably."[48]

[Footnote 48: Annual Report, 1886, Part D, pp. 33, 34.]

This author adds the further interesting detail that the underlying
Cretaceous shales are "very soft," and "have suffered very little by the
sliding of the limestone over them."[49]

About a hundred miles further south, but still in Alberta, we have the
well-known Crow's Nest Mountain, a lone peak, which consists of these
same Algonkian limestones resting on a Cretaceous valley "in a nearly
horizontal attitude," as G.M. Dawson says, which "in its structure and
general appearance much resembles Chief Mountain,"[50] another detached
peak some fifty miles further south, just across the boundary line in
Montana.

Chief Mountain has been well described by Bailey Willis,[51] who
estimates that the Cretaceous beds underneath this mountain must be
3,500 feet thick; while the so-called "thrust plane is essentially
_parallel to the bedding_" of the upper series.[52]

"This apparently is true not only of the segments of thrust surface
beneath eastern Flattop, Yellow, and Chief Mountain, but also of the
more deeply buried portions which appear to dip with the Algonkian
strata into the syncline. While observation is not complete, it may be
assumed on a basis of fact that thrust surfaces and bedding are nearly
parallel over extensive areas."[53]

[Footnote 49: