About twenty miles below Fort Good Hope there are some sandstone cliffs,[40] which Captain Franklin examined in 1825. 173, 174The sandstones are similar to those occurring higher up the river, but some of the beds contain small pieces of bituminous shale; and they are interstratified with thin layers of flinty-slate, and of flinty-state passing into bituminous shale. 175, 176The flinty-slate contains iron pyrites, and its layers are covered with a sulphureous efflorescence. Some of the beds pass into a slate-clay, which contains vegetable impressions, and some veins of clay-iron stone also appear in the cliff.
Sixty miles below Fort Good Hope the river turns to the northward, and makes a sharp elbow betwixt walls of sandstone eighty or ninety feet high, which continue for fifteen or178
179
180
181, 182
183 twenty miles. Captain Franklin named this passage of the river "The Narrows."[41] The sandstones of the Narrows lie in horizontal beds, and have generally a dark gray colour. They are parted by thin slaty beds of sandstone, containing small pieces apparently of bituminous coal, and some casts of vegetables. 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. 184, 185A 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. 186In some parts the soil has a red colour from the disintegration of a reddish-brown slate-clay. 187The summits of the hills that were visited were thinly coated with loose gravel, composed of smooth pebbles of lydian-stone, intermixed with some pieces of green felspar, white quartz, limestone, and chert. In some places almost all the pebbles were as large as a goose-egg, in others none of them exceeded the size of a hazel nut. The Rein-deer Mountains terminate in lat. 69°, having previously diminished in altitude to two hundred feet, and the eastern branch of the river turns round their northern extremity. White spruce trees grow at the base of these hills as far as lat. 68½°; north of which they become very stunted and straggling, and very soon disappear, none reaching to lat. 69°.
Sir Alexander Mackenzie, who, on his return from the sea, walked over these hills, says, "Though the country is so elevated, it is one continued morass, except on the summits of some barren hills. As I carried my hanger in my hand, I frequently examined if any part of the ground was in a state of thaw, but could never force the blade into it beyond the depth of six or eight inches. The face of the high land towards the river is, in some places, rocky, and in others a mixture of sand and stone, veined with a kind of red earth, with which the natives bedaub themselves." It was on the 14th of July that he made these observations. On the 5th of the same month, in a milder year, we found that the thaw had penetrated nearly a foot into the beds of clay at the base of the hills.
ALLUVIAL ISLANDS AT THE MOUTH OF THE MACKENZIE.
The space between the Rocky Mountains and Rein-deer Hills, ninety miles in length from lat. 67° 40' to 69° 10', and from fifteen to forty miles in width, is occupied by flat alluvial islands, which separate the various branches of the river. Most of these islands are partially or entirely flooded in the spring, and have their centres depressed and marshy, or occupied by a lake; whilst their borders are higher and well clothed by white spruce trees. The spring floods find their way, through openings in these higher banks, into the hollow centres of the islands, carrying with them a vast quantity of drift timber, which, being left there, becomes water-soaked, and, finally, firmly impacted in the mud. The young willows, which spring up rapidly, contribute much towards raising the borders of the stream, by intercepting the drift sand which the wind sweeps from the margin of the shallow ponds as they dry up in summer. The banks, being firmly frozen in spring, are enabled to resist the weight of the temporary floods which occur in that season, and before they are thawed the river has resumed its low summer level. The trees which grow on the islands terminate suddenly, in lat. 68° 40'.
I have already mentioned, that a large sheet of brackish water, named Esquimaux Lake, lies to the eastward of the Rein-deer Mountains, running to the southward, and approaching within sixty miles of the bend of Mackenzie's River at Fort Good Hope. This lake has a large outlet into Liverpool Bay, to the westward of Cape Bathurst, and there are many smaller openings betwixt that bay and Point Encounter, near the north end of the Rein-deer Hills, which are also supposed to form communications betwixt the lake and the sea. The whole coast-line from Cape Bathurst to the mouth of the Mackenzie, and the islands skirting it, as far as Garry and Sacred Islands, present a great similarity in outline and structure. They consist of extensive sandy flats, from which there arise, abruptly, hills of an obtuse conical form, from one to two hundred feet above the general level. Sandy shoals skirt the coast, and numerous inlets and basins of water divide the flat lands, and frequently produce escarpments of the hills, which show them to be composed of strata of sand of various colours, sometimes inclosing very large logs of drift timber. There is a coating of black vegetable earth, from six inches to a foot in thickness, covering these sandy hummocks, and some of the escarped sides appeared black, which was probably caused by soil washed from the summit.
It is possible that the whole of these eminences may, at some distant period, have been formed by the drifting of moveable sands. At present the highest floods reach only to their bases, their height being marked by a thick layer of drift timber. When the timber has been thrown up beyond the reach of ordinary floods, it is covered with sand, and, in process of time, with vegetable mould. The Elymus mollis, and some similar grasses with long fibrous roots, serve to prevent the sand-hills from drifting away again. Some of the islands, however, consist of mud or clay. Captain Franklin describes Garry's Island as presenting cliffs, two hundred feet high, of black mud, in which there were inclined beds of lignite. 188Specimens of this lignite have the same appearance with the fibrous wood-coal occurring in the formation at the mouth of Bear Lake River, and, like it, contain resin.189
190 Imbedded in the same bank, there were large masses of a dark-brown calc-tuff, full of cavities containing some greenish earthy substance. Some boulders of lydian stone strew the beach. The cliffs of Nicholson's Island also consisted of sand and mud, which, at the time of our visit, (July 16th,) had thawed to the depth of three feet. This island rises four hundred feet above the level of the sea, and is covered with a thin sward of grasses and bents.