posed in oblong ridges, with small mural precipices.
It has, generally, a flesh-red colour, and contains some specks of
augite, but little or no mica. The granite and porphyry were observed
only on the east side of the height of land, the brow of which, and its
whole western declivity, is formed of sandstone. Boulders of granite and
porphyry, precisely similar to the varieties which occur _in situ_ on
the height of land, are common on the beach at Fort Franklin, and on the
banks of the Mackenzie above Bear Lake.

To the westward of the height of land, the country on the banks of Dease
River is more level, and few rocks _in situ_ were seen, until within
five or six miles of Bear Lake, where the stream flows through a chasm,
whose sides are composed of a soft, fine-grained red sandstone, like
that which occurs in the vale of Dumfries, in Scotland. Several ravines
here have their sides composed of fine sand, inclosing fragments of soft
sandstone.

About three miles from the mouth of Dease River we came to a limestone
formation, which has been already noticed in the account of the
geological structure of the shores of Great Bear Lake.

EASTERN CHAIN OF PRIMITIVE ROCKS.

The preceding part of the paper describing the rock formations which
were noticed on the route of the expedition from Great Slave Lake down
the Mackenzie along the shores of the Arctic Sea, the Coppermine, Great
Bear Lake, and Great Bear River, being a distance of three thousand
miles, I shall, by way of supplement, mention very briefly some of the
more southern deposits.

The first I have to speak of is the chain of primitive rocks to which I
have alluded in page 289, as extending for a very great distance in a
north-west direction, and inclining in the northern parts slightly
towards the Rocky Mountain Chain. Dr. Bigsby, in his account of the
geology of Lake Huron says, that "The primitive rocks on the northern
shores of that lake are part of a vast chain, of which the southern
portion, extending probably uninterruptedly from the north and east of
Lake Winipeg, passes thence along the northern shores of Lakes Superior,
Huron, and Simcoe, and after forming the granitic barrier of the
Thousand Isles, at the outlet of Lake Ontario, spreads itself largely
throughout the state of New York, and there joins with the Alleghanies,
and their southern continuations." It is not my intention to say any
thing further of the rocks in the districts of which Dr. Big