sby speaks,
although in travelling from the United States to Lake Winipeg the
expedition passed over them. That zealous geologist has already given,
in various publications, many interesting and accurate details of the
formations on the borders of the great lakes; an account of those which
lie some degrees farther to the north is inserted in the second volume
of the Geological Transactions,--and there are some notices of them in
the Appendix to the narrative of Captain Franklin's First Journey. My
object at present is, merely to trace the western boundary of the
primitive rocks in their course through the more northerly parts of the
American continent.

I have already quoted Sir Alexander Mackenzie's original and important
remark, of the principal lakes in those quarters being interposed
betwixt the primitive rocks and the secondary strata, lying to the
westward of them--Lake Winipeg is an instance in point. It is a long,
narrow lake, and is bounded throughout on its east side by primitive
rocks, mostly granitic, whilst its more indented western shore is formed
of horizontal limestone strata. The western boundary of the primitive
rocks, extending on this lake about two hundred and eighty miles, has
nearly a north-north-west direction. From Norway Point, at the north end
of the lake, to Isle a la Crosse, a distance of four hundred and twenty
miles in a straight line, the boundary has a west-north-west direction.
For two hundred and forty miles from Isle a la Crosse to Athabasca Lake,
the course of the primitive rocks is unknown to me; but from Athabasca
Lake to M'Tavish's Bay, in Great Bear Lake, a distance of five hundred
miles, their western edge runs about north-west-by-west, and is marked
by the Slave River, a deep inlet on the north side of Great Slave Lake,
and a chain of rivers and lakes, (including great Marten Lake,) which
discharge themselves into that inlet.

Captain Franklin on his voyage crossed this primitive chain nearly at
right angles to its line of direction, in proceeding from Hudson's Bay
to Lake Winipeg--it was there two hundred and twenty miles wide.

The hills composing the chain are of small elevation, none of them
rising much above the surrounding country. They have mostly rounded
summits, and they do not form continuous ridges; but are detached from
each other, by vallies of various breadth, though generally narrow, and
very seldom level. The sides of the hills are steep, often precipitous.
W