16

range on the east, do cross the river with undiminished strength at Hell Gate and
probably merge with some of the southern spurs of the Mackenzie mountains to
the northward.

The whole of this portion of the Cordilleran province is drained by three
principal streams, the Athabaska, Peace, and Liard rivers. These rivers have
their sources either in the central ranges of the Rockies or in the western slopes,
but flow eastward by transverse gaps from the central ranges through a broad
belt of foothills to the Great Central plain.

_ Mackenzie Mountains. Mackenzie mountains represent the Cordillera from
the Liard river to the Peel and are the northwestern continuation of the Rocky
mountains. They resemble the Rocky mountains in general characteristics and
are made up of a series of parallel ranges striking northwesterly in the southern
part and almost east and west in the northern part. “ They are the greatest moun-
tain group in Canada and appear to consist of two ranges, an older western range,
against the eastern edges of which a newer range has been piled.” The newer
range as well as a part of the older range lies on the Mackenzie River slope of the
divide. E

Mackenzie mountains have been crossed in only two places, namely, on Gravel
river by Keele and on Wind river by Camsell. Their eastern front, however, °
was ascended and examined by McConnell at Liard river and North Nahanni
river. At the south they rise somewhat abruptly out of a low-lying level region
to heights of about 6,000 feet, and on Gravel river the highest summits reach a
maximum of 8,000 feet. To the north they decrease again in elevation and on
Wind river rarely reach 7,000 feet. They appear to die away at the headwaters
of Peel river in a comparatively low region broken only by a few fault scarps and
anticlinal ridges. : )

A number of important streams have their sources in and traverse Mackenzie
mountains. Those tributary to the Mackenzie are the Nahanni, Root, Gravel,
Carcajou, Arctic Red, and Peel rivers. These all cut across the strike of the
ranges and their valleys are often continuous across the divide with those draining
to Yukon. : All the streams have such high gradients that in no case do the
natives make use of them when travelling from the valley of the Mackenzie into
the mountains. They do, however, descend many of them in boats.

_ The divide at the head of Gravel river is given by Keele as 4,525 feet, but.
there are other passes leading to the headwaters of Macmillan and Stewart rivers
which are said to be well below this level. ‘The pass at the head of Wind river
is estimated by Camsell at 3,400 feet. The vertical relief along the explored
routes through these mountains ranges from 3,000 to 4,500 feet.

Richardson Mountains. North of Peel river, or from latitude 66 degrees,
the Cordillera is represented by the Richardson mountains, a range which extends
northward along the west side of Peel river to the delta of the Mackenzie where *
it swings westward as a coastal range bordering the Arctic coast.

These mountains are considerably lower in general elevation and have neither
the length nor the breadth of Mackenzie mountains. They strike north and south
and present other features which differ greatly from the other mountains of the
Cordillera. McConnell? describes them as consisting essentially of two ranges

1Keele, J., “A reconnaissance across the Mackenzie mountains,” Geol. Surv., Can..

1910, No. 109-7.
2 Geol. Surv., Can., vol. IV, 1888-89, p. 119 D.