About fifty miles below Bear Lake River there is an almost precipitous cliff of bituminous-shale, one hundred and twenty feet high, strongly resembling the cliffs which occur near the bases of the hill of Scented-Grass and Great Bear Mountain in Bear Lake already described[34], and at the mouth of the Clear Water River in lat. 56½°. In the two former localities the shale is in the neighbourhood of horizontal strata of limestone; and in the latter it actually reposes on the limestone, which extends in horizontal strata as far as Great Slave Lake, is connected with many salt springs, and possesses many of the characters ascribed to the zechstein formation. 133Captain Franklin observed the beach under the shale cliffs of the Mackenzie to be strewed not only with fragments of the shale, but also with much lignite, similar to that which occurs at the mouth of the Bear Lake River. Twelve or fourteen miles below these cliffs there is a reach seventeen or eighteen miles long, bounded by walls of sandstone in horizontal beds. 134
135 Specimens obtained by Captain Franklin at the upper end of the reach consist of fine-grained quartzose sandstone[35] of a gray colour, and having a clayey basis, resembling those which occur in the middle of Bear Lake River. At the commencement of the "Great Rapid of the Mackenzie" there is a hill on each side of the river, named by Captain Franklin the eastern[36] and Western mountains of the Rapid. The Rocky Mountains appear at no great distance from this place, running about N.W. by W., until lost to the sight; and as the Mackenzie for forty or fifty miles below, winds away to the northward, and, in some reaches, a little to the eastward, they are not again visible, until the river has made a bend to the westward, and emerges from the defile termed "the Narrows."
The "Eastern mountain of the rapid" seems to have a similar structure, with the "Hill by the River's side," the hill at the mouth of Bear Lake River, and the other limestone ridges which traverse this part of the country. 136From some highly inclined beds near its base I broke off specimens of a limestone, having an imperfectly crystalline structure, and a brown colour, which deepens into dull black on the surfaces of its natural seams. A piece of dark-gray, compact limestone, having the peculiar structure137
138 to which the name of "cone in cone" has been given, was found on the beach; also several pieces of chert, and some fragments 139
141of a trap-rock, consisting of pieces of greenstone, more or less iron-shot, cemented by calc-spar.
Immediately below the rapid there are horizontal layers of sandstone which form cliffs, and also the bed of the river. Captain Franklin obtained specimens of this stone, which do not differ from the sandstones above the rapid. 142
143
140 And amongst the debris of the cliff he found other specimens of the "cone in cone," such as it occurs in the clayey beds of the coal measures, and also some pieces of crystallized pyrites.
About forty miles below the rapid, the river flows through a narrow defile formed by the approach of two 144
144a
145
146
147
144blofty banks of limestone in highly-inclined strata, above which there is a dilatation of the river, bounded by the walls of sandstone, which have weathered, in many places, into pillars, castellated forms, caves, &c. The sandstone strata are horizontal, have slate-clay partings, and seams of a poor clay-iron stone, but do not differ in general appearance from the sandstone beds at the rapid, except that a marly stone containing corallines, and having the general colour and aspect of the sandstone beds, is associated with them at this place.
The very remarkable defile, below these sandstone beds, is designated "the second rapid" by Sir Alexander Mackenzie, and "the ramparts" by the traders, a name adopted by Captain Franklin. Mackenzie states it to be three hundred yards wide, three miles long, and to have fifty fathoms depth of water. If he is correct in his soundings, its bed is probably two hundred and fifty feet below the level of the sea. The walls of the defile rise from eighty to one hundred and fifty feet above the river, and the strata are inclined to the W.N.W., at an angle of seventy or eighty degrees. It is worthy of remark, that the course of the river through this chasm is E.N.E., and that just above the eastern mountain of the rapid it runs about W.S.W. through the sandstone strata, as if it had found natural rents by which to make its escape through the ridge of hills which cross its course here. Similar elbows occur in various parts of the River, and they may be almost always traced to some peculiarity in the disposition of the hills which traverse the country.
Captain Franklin gathered many specimens of the limestone strata of the Ramparts, which are specified in a note.[37] 148, 149Some of the beds at the upper part of the Ramparts consist of a granular foliated limestone, which was not noticed elsewhere on the banks of the river, but the greater part are of limestone, strongly resembling that which has been already described, as forming the ridges in this quarter. Most of the beds are impregnated wholly, or in patches, with bitumen. Some of these specimens contain corallines and terebratulæ; and at the lower end of the defile there are horizontal strata of limestone, covered by a thin layer of flinty slate.
Below the ramparts the river expands to the width of two miles, and for a reach or two its banks are less elevated. In lat. 66¾°, about thirty miles from the ramparts, there are cliffs which Captain Franklin in his notes, remarks, "run on an E. by S. course for four miles, are almost perpendicular, about one hundred and sixty feet high, and present the same castellated appearances that are exhibited by the sandstone above the defile of the "ramparts." 159, 160,
161, 162
163, 164,
165, 166
167, 168,
169, 170The cliffs[38] are, in fact, composed of sandstones similar, in general appearance, to those which occur higher up the river; but some of the beds contain the quartz in coarser grains, with little or no cement. The beds are horizontal, and repose on horizontal limestone,[39] from which Captain Franklin broke many specimens in 1825. We landed at this place in 1826 to see the junction of the two rocks, but the limestone was concealed by the high waters of the river. Captain Franklin's specimens are full of shells, many of which are identical with those of the flat limestone strata of the Athabasca River. 171 One bed appears to be almost entirely composed of a fine large species of terebratula, not yet described, but of which Mr. Sowerby has a specimen from the carboniferous limestone of Neho, in Norway. Some of the beds contain the shells in fragments; in others, the shells are very entire.
About forty miles below these sandstone walls the banks of the river are composed of marl-slate, which weathers so readily, that it forms shelving acclivities. 172In one reach the soft strata are cut by ravines into very regular forms, resembling piles of cannon shot in an arsenal, whence it was named Shot-reach.
The river makes a short turn to the north below Shot Reach, and a more considerable one to the westward, in passing the present site of Fort Good Hope. The banks in that neighbourhood are mostly of clay, but beds of sandstone occasionally show themselves. The Indians travel from Fort Good Hope nearly due north, reach the summit of a ridge of land on the first night, and from thence following the course of a small stream they are conducted to the river Inconnu, and on the evening of the 4th day they reach the shores of Esquimaux Lake. Its water is brackish, the tide flowing into it. The neck of land which the Indians cross from Fort Good Hope is termed "isthmus" on Arrowsmith's map, from Mackenzie's information; and its breadth, from the known rate at which the Indians are accustomed to travel, cannot exceed sixty miles. The ridge is named the Carreboeuf, or Rein-deer Hills, and runs to lat. 69°, forming a peninsula between the eastern channel of the Mackenzie and Esquimaux Lake.
A small stream flows into the Mackenzie some way below Fort Good Hope, on the banks of which, according to Sir Alexander Mackenzie, the Indians and Esquimaux collect flints. He describes these banks as composed of "a high, steep, and soft rock, variegated with red, green, and yellow hues; and that, from the continual dripping of the water, parts of it frequently fall, and break into small, stony flakes, like slate, but not so hard. Amongst these are found pieces of petroleum, which bears a resemblance to yellow wax, but is more pliable." The flint he speaks of is most probably flinty-slate; but I do not know what the yellow petroleum is, unless it be the variety of alum, named rock-butter, which was observed in other situations, forming thin layers in bituminous shale.