g Vancouver Island and
the Queen Charlotte Islands. The highest mountains of the Cordillera in
Canada are near the southern end of the boundary separating Alaska from
the Yukon Territory, the meridian of 141 deg., and they include Mount
Logan (19,540 ft.) and Mount St Elias (18,000 ft.), while the highest
peak in North America, Mount McKinley (20,000 ft.), is not far to the
north-west in Alaska. This knot of very lofty mountains, with Mount
Fairweather and some others, all snowy and glacier-clad for almost their
whole height, are quite isolated from the highest points of the Rocky
Mountains proper, which are 1000 m. to the south-east. Near the height
of land between British Columbia and Alberta there are many peaks which
rise from 10,000 to 12,000 ft. above sea-level, the highest which has
been carefully measured being Mount Robson (13,700 ft.). The next range
to the east, the Selkirks, has several summits that reach 10,000 ft. or
over, while the Coast Ranges scarcely go beyond 9000 ft. The snow line
in the south is from 7500 to 9000 ft. above sea-level, being lower on
the Pacific side where the heaviest snowfall comes in winter than on the
drier north-eastern side. The snow line gradually sinks as one advances
north-west, reaching only 2000 or 3000 ft. on the Alaskan coast. The
Rockies and Selkirks support thousands of glaciers, mostly not very
large, but having some 50 or 100 sq. m. of snowfield. All the glaciers
are now in retreat, with old tree-covered moraines, hundreds or
thousands of feet lower down the valley. The timber line is at about
7500 ft. in southern British Columbia and 4000 ft. in the interior of
the Yukon Territory. On the westward slopes, especially of the Selkirks
and Coast Ranges, vegetation is almost tropical in its density and
luxuriance, the giant cedar and the Douglas fir sometimes having
diameters of 10 ft. or more and rising to the height of 150 ft. On the
eastern flanks of the ranges the forest is much thinner, and on the
interior plateau and in many of the valleys largely gives way to open
grass land. The several ranges of the Cordillera show very different
types of structure and were formed at different ages, the Selkirks with
their core of pre-Cambrian granite, gneiss and schists coming first,
then the Coast Ranges, which seem to have been elevated in Cretaceous
times, formed mainly by a great upwelling of granite and diorite as
batholiths along the margin of the continent and sedimentary r