[Sidenotes: 180, 181, 182] They are parted by thin
slaty beds of sandstone, containing small pieces apparently of
bituminous coal, and some casts of vegetables. [Sidenote: 183] Most of
the beds contain scales of mica, and some of them have nodules of
indurated iron-shot clay which exhibit obscure impressions of shells. A
bed of imperfectly crystalline limestone was seen by Captain Franklin
underlying the sandstones.

MACKENZIE RIVER BELOW "THE NARROWS."

The Mackenzie, on emerging from the Narrows, separates into many
branches, which flow to the sea through alluvial or diluvial deltas and
islands. The Rocky Mountains are seen on the western bank of the river,
forming the boundary of those low lands; and the lower, but decided
ridge, of the Rein-deer Hills holds nearly a parallel course on the east
bank. The estuary lying between these two ranges, opens to the N.W. by
N. into the Arctic Sea. I have already mentioned the specimens of rocks
obtained at the few points of the Rocky Mountains that were visited,[42]
and therefore shall now speak only of the Rein-deer Hills. We did not
approach them until we had passed for thirty miles down a branch of the
river which winds through alluvial lands. At this place there are
several conical hills about two hundred feet high, which appeared to
consist of limestone. Specimens taken from some slightly-inclined beds
near their bases, consisted of a fine-grained, dark, bluish-gray
limestone. After passing these limestone rocks, the Rein-deer Hills were
pretty uniform in appearance, having a steep acclivity with rounded
summits. Their height, on the borders of the river, is about four
hundred feet, but a mile or two inland they attain an elevation of
perhaps two hundred feet more. Their sides are deeply covered with sand
and clay, arising most probably from the disintegration of the subjacent
rocks. [Sidenote: 184, 185] A section made by a torrent, showed the
summit of one of the hills to be formed of gray slate-clay, its middle
of friable gray sandstone much iron-shot, and its base of dark
bluish-gray slaty clay. The sandstone predominates in some parts of the
range, forming small cliffs, underneath which there are steep
acclivities of sand. It contains nearly an equal quantity of black
flinty slate, or lydian stone, and white quartz in its composition, and
greatly resembles the friable sandstones of the lignite formation at the
mouth of Bear Lake River. [Sidenote: 186] In some part