a

5,000 feet in height. The valley bottom has an elevation of about
3,300 feet and the distance’ from the Rocky Mountain front is only ..

5 miles. Eastward, pink granite and gneissoid boulders are more
numerous. On Teepee. Mountain (mile 64 circa) they occur above an
elevation of 4,000 feet. On the other hand, boulders of Silurian
limestone, of Silurian’or Devonian sandstone, and of the local Pre-
cambrian rocks indicate that the main drift was from the west... Val-
ley glaciers account for the movement of rock debris from the moun-
tains to the plains areas, but the origin of grey granodiorite boulders,
apparently of Coast Range type, is not known.

Outwash gravel forms terraces of note along the valleys of
the foothills and mountains.. These deposits include till on their
flanks and in places at the base, but they consist for the most part
of well-rounded coarse gravel of local origin. Notable gravel terraces
extend through Summit Pass (elevation 4,100 feet) to a height of about
4,700 feet. These terraces extend westward down MacDonald Creek to
Racing River and eastward far down Tetsa River. The present streams
have excavated their channels into these gravels, in places well down
to rock bottom. Elsewhere old channel bottoms may be several hundreds
of feet’ ‘below the present.channel, The Summit Lakes and Muncho [ake
are-in-dammed segments of valleys. Bh pote

Similar terraces are well preserved along Trout River in
the vicinity of mile 197. Gravel extends from the river level, at an
elevation of about 2,250 feet, to an elevation of 2,400 feet, These
examples are typical of the almost universal presence of terraces
along the mountain valleys. Deep glaciated valleys were filled with
till and outwash gravel mostly of local origin, and later, streams
and rivers formed their present valleys and beds. How unstable are
present conditions was well demonstrated during the floods of July 10
and August 2, when forested river bars were cut away, sand banks cut
out, and river channels completely changed in a few hours time. Muskwa
River near Fort Nelson ‘is reported to have risen Kok ‘feet “in 30 hours.

Great sand plains, in part covered with shallow muskeg,
extend eastward from the front of the Foothills, and Liard River Valley
consists of broad terraces of sand plains below which the river has
cut its present channels. Long stretches of smooth water are flanked
by sand and gravel banks, and the intervening canyons mark the super-
position of the present stream across spurs in the pre-glacial valley.
West of Smith River, for more than 25 miles to the north, wide sand
plains extend to undetermined distances. The outwash sand and gravel
give some measure of the quantity of debris liberated by the be OB cae
ice-sheet.

ECONOMIC POSSIBILITIES
Mineral Deposits

According to Dawson, Messrs. Thibert and McCulloch dis-
covered gold near Fort Halkett in 1872. They also discovered’ gold in
the Cassiar and a rush followed. The total yield for the district up
to 1874 is reported as $1,000,000. In 1875 the yield was $830,000 and
in 1876 the amount fell to $499,850. Gold was found on bars in Liard
River as far down as 8 miles below the mouth of Coal River. As no
separate record was kept of Liard River production, the values taken
fron the bars cannot be determined. Most of the gold obtained came
from Dease River and Cassiar districts and recent prospecting along
the Liard has produced little «

The northern Rocky Mounteins, like their more southern
counterparts, contain little in the way of mineral deposits. Purple
fluorite occurs in Silurian (?) limestone near mile 107 and near the