Chapter XVII: Appendix (1)

TOPOGRAPHICAL AND GEOLOGICAL NOTICES, BY JOHN RICHARDSON, M.D., F.R.S., &c. SURGEON AND NATURALIST TO THE EXPEDITION.

[_Read before the Geological Society._]

A very limited portion of my time could be allotted to geological inquiries. For eight months in the year the ground in the northern parts of America is covered with snow; and during the short summer, the prosecution of the main object of the expedition rendered the slightest delay in our journey unadvisable. The few hours that could be stolen from the necessary halts, for rest and refreshment, were principally occupied in the collection of objects for the illustration of botany and zoology. It is evident, that an account of the rock formations, drawn up under such circumstances, cannot be otherwise than very imperfect; but I have been led to publish it from the belief that, in the absence of more precise information, even the slightest notice of the rocks of the extreme northern parts of the American continent would be useful to those employed in developing the structure of the crust of the earth; the more especially, as it is not probable that the same tract of country will soon be trod by an expert geologist. The specimens of rocks I obtained have been deposited in the Museum of the Geological Society, and are referred to in the ensuing pages by the numbers affixed to them. The notices are arranged nearly in the order of the route of the expedition, commencing with Great Bear Lake, where our winter quarters were situated.

GREAT BEAR LAKE.

Great Bear Lake is an extensive sheet of water, of a very irregular shape, being formed by the union of five arms or bays in a common centre. The greatest diameter of the lake, measuring about one hundred and fifty geographical miles, runs from the bottom of Dease Bay, which receives the principal feeding stream, to the bottom of Keith Bay, from whence the Bear Lake River issues, and has a direction from N.E. to S.W. The transverse diameter has a direction from N.W. by W. to S.E. by E., through Smith and M'Tavish Bays, and is upwards of one hundred and twenty miles in length. M'Vicar Bay, the fifth arm of the lake, is narrower than the others, and being a little curved at its mouth, appears less connected with the main body of water. The light bluish-coloured water of Great Bear Lake is every where transparent, and is particularly clear near some primitive mountains, which exist in M'Tavish Bay. A piece of white rag, let down there, did not disappear until it descended fifteen fathoms. The depth of water, in the centre of the lake was not ascertained; but it is known to be very considerable. Near the shore, in M'Tavish Bay, forty-five fathoms of line did not reach the bottom. Owing to the barometers supplied to the expedition having been broken in an early period of its progress, the height of the surface of Bear Lake above the Arctic Sea could not be ascertained; but it is, probably, short of two hundred feet.[20] If this supposition comes near the truth, the bottom of M'Tavish Bay is below the level of the sea, and towards the centre of the basin of the lake the depression is probably still greater. The great lakes, Huron, Michigan, and Superior, which discharge their waters into the St. Lawrence, are reported to sink three hundred feet below the level of the ocean; and the Lake of the Mountains, or Chipewyan Lake and Great Slave Lake,[21] through which the Mackenzie flows, have, it is highly probable, some portions of their beds below the sea level.

In the autumn of 1825, I coasted the western and northern shores of the Great Bear Lake; and in the spring of 1826, travelled on the ice along its eastern and southern arms, leaving no part of its shores unexamined on these two surveys, except the north side of M'Tavish Bay. I did not, however, on these occasions, make excursions inland.

PRIMITIVE ROCKS.--GREAT BEAR LAKE.

At the south-east corner of M'Tavish Bay, primitive rocks form a hilly range which, at the distance of a mile or two from the shore, attains an elevation of eight hundred or one thousand feet. The steep face of the range forms the shore of the lake for fifteen miles, and perhaps further, on a direction from N.W. by W. to S.E. by E., and is prolonged on the latter bearing, at the back of the lower country lying towards Point Leith. The general form of the hills is obtuse-conical, in some instances approaching to dome-shaped. None of them rise much above the others, and the vallies between them are seldom wide or deep. At a distance, some of the masses of rock appear round-backed; and in certain points of view, the crest of the ridge seems to consist of mammillary peaks. On a nearer approach, the individual hills are found to be composed of rounded eminences, having summits, generally, of an oblong form, and consisting of smooth, naked rock. Small mural precipices are frequent, and many detached blocks of stone lie beneath them. Between the eminences, there are level spots destitute of vegetation, and covered with small stones or gravel not much worn. A considerable portion of the gravel is granite or quartz, the debris, perhaps, of the rocks, of which the hills consist; it contains also some pieces of slate, and not a few of quartzose sandstone, neither of which I observed _in situ_. In the course of a walk of two miles over these hills, the only rock I observed was granite, verging in a few places towards gneiss, and generally whitish, with black mica. Sometimes the felspar is brownish-red, and the rock not unfrequently contains disseminated augite? The weathered surface of the stone was every where of a brick-red colour. In many spots the rocks split into such thin slaty looking tables that they have the appearance of being stratified. The slaty masses are, generally, vertical; but in one hill they were observed dipping 80 degrees to the south-east. The direction of the tabular masses is mostly across the oblong summits of the hills. The appearances of stratification were not observed to extend through a whole hill, and seemed, in fact, to be confined to the more decomposable granites; but the naked rocks are every where traversed by smooth fissures. The blocks, which lie under the cliffs, have sometimes a tabular form, but more generally come nearer to a cube or rhomboid, and present one or two very even faces. Few veins were noticed. In the more sheltered vallies, some clumps of white or black spruce trees occur; but the hills are barren.

The point of land which lies between M'Tavish and M'Vicar Bays has low shores; but five or six miles inland, an even-backed ridge rises gradually to the height of three or four hundred feet, and abuts obliquely against the primitive hills. I did not visit this ridge, and the snow prevented me from seeing any flat beds of rocks, if such exist on the shore. On one point, however, near the north end of Dease Bay, many large angular blocks of whitish dolomite were piled up, and I have little doubt of the rock existing _in situ_ in that immediate neighbourhood.

M'Tavish Bay is forty miles long, and twenty wide, and its depth of water, near the eastern shore, exceeds forty-five fathoms. Some shoals of boulders skirt the coast near Point Leith. M'Vicar Bay is about seventy miles long, and from eight to twelve wide; and at the "fishery," in a narrow part, not far from its bottom, its depth of water, two miles from the shore, is twelve fathoms. Dease Bay is equal to M'Tavish Bay in extent, and opens to the S.W. into the body of the lake. The high lands at the N.E. end, or bottom of this bay, have an even outline, and appear to attain an elevation of eight or nine hundred feet, at the distance of six or seven miles from the shore. Near its east side lie the lofty islands of Narrakazzae which rise seven hundred feet above the lake. Dease River, the principal feeder of the lake, falls into the bottom of Dease Bay. It is two hundred yards wide, and from one to three fathoms deep near its mouth. A few miles up this river a formation of soft red sandstone occurs, which will be noticed hereafter.

LIMESTONE.--GREAT BEAR LAKE.

[Sidenote: 228*] At the mouth of Dease river there are hills five or six hundred feet high, composed principally, or entirely, of dolomite in horizontal strata. Some of the beds consist of a thick-slaty, fine-grained dolomite, containing dispersed scales of mica, which is most abundant on the surfaces of the slates. [Sidenote: 228] Most of the beds, however, consist of a thin-slaty, dull, purplish dolomite, traversed by veins of calc-spar. The structure of this rock is compact, approaching to fine granular; and some of the beds have what quarry-men term "clay-facings," that is, they are encrusted with a thin film of indurated clay.

Greenstone slate? occurs in horizontal beds on the north shore, eight or nine miles to the westward of Dease River: and at Limestone Point,[22] about twenty miles from the river, a small range of hills terminates on the borders of the lake, in shelving, broken cliffs, about two hundred feet high. These cliffs consist chiefly of nearly compact light-coloured dolomite, interstratified with greenstone, and a brownish-red limestone, such as occurs in the hills at the mouth of the Dease River. In contact with the greenstone, there is a bed of talcose limestone, having a curved, slaty structure; most of the beds of dolomite are hard, and pass into chert.

ALUMINOUS SHALE.--GREAT BEAR LAKE.

The north shore of Bear Lake is low, and is skirted by many shoals, formed by boulders of limestone. No rocks, _in situ_, are exposed between Limestone Point and the Scented Grass Hill, a remarkable promontory, which separates Smith and Keith bays. Its height above the lake is betwixt eight and nine hundred feet, and in form and altitude it corresponds with the Great Bear Mountain, which, lying opposite to it, separates M'Vicar and Keith bays. I did not ascend either of these hills; but cliffs, corresponding in character to those of the aluminous shale-banks at Whitby, flank their bases; and the same formation probably extends along the north shore of Keith Bay, and some way down Bear Lake River. The ground skirting the Scented Grass and Great Bear Mountains is much broken, and consists of small, rounded and steep eminences, separated by narrow vallies and small lakes. Several shelving cliffs, about one hundred feet high, and some miles in extent are washed by Bear Lake. [Sidenote: 251] They consist of slate-clay and shale, more or less bituminous, and the dip of the strata is in several places to the N.W. by N. [Sidenotes: 244, 246, 247] At the foot of the Scented Grass Hill a rivulet has made a section to the depth of one hundred feet, and here the shaly beds are interstratified with thin layers of blackish-brown, earthy-looking swinestone, containing selenite and pyrites. Globular concretions of the same stone, and of a poor clay iron-stone, also occur in beds in the shale. [Sidenotes: 249, 250, 248] The surfaces of the slates were covered with an efflorescence of alum and sulphur. Many crystals of sulphate of iron lie at the bottom of the cliff, and several layers of plumose alum, half an inch thick, occur in the strata. At the base of Great Bear Mountain, the bituminous shale is interstratified with slate-clay, and I found imbedded in the former a single piece of brown coal, in which the fibrous structure of wood is apparent. Sections of slate-clay banks, and more rarely of bituminous shale, occur in several places on the north shore of Keith Bay. In one place, about seven or eight miles from Bear Lake River, a bed of plastic and bituminous clay occurs, and in another, near Fort Franklin, there is a deposit of an earthy coal, which possesses the characters of _black chalk_.

It is probable that a magnesian limestone underlies this formation of bituminous shale. I have already mentioned the beds of dolomite, which are exposed on the north side of Bear Lake, and similar beds occur to the southward of the Great Bear Mountain, forming cliffs on the shores of M'Vicar Bay. At Manito Point, on the west side of the isthmus that connects Great Bear Mountain to the main shore, a low ridge of limestone rocks terminates on the borders of the lake, forming some bold cliffs and a remarkable cave. The stone has a gray colour and bituminous smell, and contains much interspersed calc-spar. The strata dip to the north-west.

VICINITY OF FORT FRANKLIN, GREAT BEAR LAKE.

Fort Franklin stands on the northern shore of Keith Bay, about four miles from Bear Lake River, upon a small terrace, which is elevated twenty-five or thirty feet above the lake. The bay, contracting towards the river, is about four miles wide opposite to the fort, and the depth of water there does not exceed four fathoms. Farther from the river, the east and west shores of Keith Bay recede to the distance of thirty miles from each other, and the depth of water in the centre of the channel greatly increases. The bottom of this bay, wherever it could be distinguished, was observed to be sandy, and thickly strewed with round boulders[23] of various primitive rocks of large size, which were particularly abundant near the river, and with large square blocks of limestone, most plentiful near the cape formed by the Scented Grass Hill. In the small bay between the fort and the river, shoals are formed by accumulations of boulders, and the shores are thickly strewed with them. [Sidenote: 261 to 308] Many of these travelled blocks consist of flesh-red granite, having only a small quantity of black mica, exactly resembling the primitive rocks seen in M'Tavish Bay, but noticed no where else near the lake. Boulders of the same description occur in shoals at the mouth of M'Tavish Bay, and on the shores which skirt the Scented Grass Hill which faces that bay, to all which places they may have been brought from the parent rock, by a current flowing from the east. On the northern shore of Bear Lake the great majority of the boulders consists of limestone. [Sidenote: 266 282] Two varieties of granite, which occur amongst the boulders, were recognised as being abundant rocks at Fort Enterprise, which is situated about one hundred and seventy miles south-east from M'Tavish Bay. Some of the boulders were of a peculiar-looking porphyry exactly resembling that which occurs in the height of land betwixt the Coppermine River and Dease Bay; several of sandstone and conglomerate, which probably came from the same quarter; of greenstone, perhaps, from the Copper Mountains, and of limestone from the northern shores of the lake, and from the isthmus of the Great Bear Mountain; all these places lying to the eastward or north-east.

The soil in the immediate vicinity of Fort Franklin is sandy, or gravelly, and covers, to the depth of one or two feet, a bed of clay of unknown thickness. Gravel taken from a spot thirty feet above the present high-water level of the lake, and out of the reach of any stream or torrent, contained rounded pebbles of granite, of greenstone, of quartz rock, of lydian stone, and of various sandstones, of which some were spotted, and others presented zones of different colours. These sandstones form a considerable portion of the gravel.[24]

The clay which lies under the soil is of a bluish-gray colour, and is plastic but not very tenacious. It is more or less mixed with gravel. During the greater part of the year it is firmly frozen; the thaw in the two seasons we remained there never penetrating more than twenty-one inches from the surface of the earth. In spots where the sandy soil is wanting, the clay is covered a foot deep, or more, by mosses, mostly _bryum palustre_, and some marsh _hypna_ and _dicrana_, in a living state, for they seem to be converted very slowly into peat in this climate.

The ground rises gradually behind the fort, until it attains, at the distance of half a mile from the lake, the height of two hundred feet, forming, when viewed from the southward, an even ridge, running nearly east and west--which ridge is, in fact, the high bank of the lake, as it corresponds in height with the summit level of the banks of Bear Lake River, and of the southern shore of Keith Bay. The country extending to the northward, from the top of the bank, is nearly level, or has a very gentle ascent for about five miles, when a more abrupt ridge rises to perhaps three hundred or four hundred feet above the lake. The view from the summit of this second eminence is very extensive, the whole country as far as the eye can reach appearing to be a level, from which several narrow precipitous ridges of limestone arise. But, although the country around these ridges appears from a distance to be level, or very slightly undulated, yet it abounds in small eminences and steep-sided vallies of various shapes, some being rounded and basin-shaped, others long and narrow. Lakes and swamps are here so numerous, that the country, for at least sixty miles to the northward, is impassable in summer, even to the natives. There are many mounds of sand and gravel, and fragments of sandstone are frequent; but having travelled in this direction only in winter, when the ground was covered to the depth of upwards of three feet with snow, I had not an opportunity of examining its geological structure. White spruces cover the drier spots; larches, black spruces, and willows abound in moist places; the sandy hillocks are clothed with aspens, and the sides of the vallies support some canoe birches, with a thick undergrowth of dwarf birches, alders, and rose-bushes. The eminence from whence the view just described was obtained, appears like a ridge only in approaching it from the lake, for it rises very little above the general level of the country behind it. It has a direction from N.W. by N. to S.E. by S., and terminates about eight miles to the eastward of the fort, in a small bluff point on the shores of the lake and there the strata consist of slate-clay slightly bituminous. The banks immediately behind the fort also exhibit, in their ravines, a bluish slate-clay.

The land on the south side, or bottom, of Keith Bay, presents a nearly similar aspect to that just described, rising, on the borders of the lake, to the height of one hundred and fifty feet, and then running back to a great distance nearly level. It may be characterized as full of hollows, narrow vallies, ravines, and lakes; but it is not hilly, although it is traversed by ridges of limestone, which rise like walls through the flat country. The nearest of these ridges terminates on the borders of the lake at the _Manito Point_, (noticed in page vii.) It may be proper to remark here, that, in addition to the limestone ridges visible from Fort Franklin, or from the heights behind it, the summit of Clark Hill, bearing south, and forming part of a ridge about fifty miles distant, was distinctly seen. This hill lies behind Old Fort Norman on the Mackenzie, and has more the outline of a granitic rock, although some of the peaks which skirt it have the serrated crests which the limestone ridges in this quarter show. It was guessed to be 1500 feet high above the Mackenzie.

This sketch of the general features of the country about Fort Franklin being premised, the ensuing geological notices follow in the order of the route of the Expedition.

BEAR LAKE RIVER--SANDSTONE, LIMESTONE.

Bear Lake River is about seventy miles long, from its origin in the lake till it falls into the Mackenzie, and throughout its whole length, its breadth is never less than one hundred and fifty yards, except at the _Rapid_, a remarkable place, about the middle of its course. It is from one to three fathoms deep, and very rapid, its velocity being estimated at six miles in the hour. Its waters are clear as they issue from the lake, but several branches of considerable size bring down muddy water, particularly one which flows from the north, and falls in below the rapid.

Above the rapid, the valley of the river is very narrow, the banks every where sloping steeply from the level of the country. Their summit line, which is nearly straight, is about one hundred and fifty feet above the bed of the river. In some places they have an even face elevated at an angle of about forty-five degrees, and they are not unfrequently cut by ravines into pretty regular figures, resembling hay-ricks, or the parapet of a fort, the ravines representing the embrasures. Sections made by the river presented generally sand or clay; the sand probably proceeding from the disintegration of a friable, gray sandstone, which showed itself occasionally in a more solid form. The rapidity of our voyage, however, afforded us little opportunity of searching for the solid strata which are generally hid by the debris of the bank. About twelve miles above the rapid, a small-grained, friable sandstone, of a yellowish gray colour, and irregular earthy fracture, is associated with beds of bluish-gray slate-clay. These beds consist of concretions of various sizes and irregular shapes, but which may be said to approach in general to a depressed orbicular form; their surfaces are coloured purplish-brown by iron, and studded with crystals of sulphate of lime. This slate-clay contains many small round grains of quartz, and is exactly similar to that which occurs at the rapid, and which will be afterwards noticed. In other places the banks are covered by the debris of a slate-clay slightly bituminous, resembling wacke in its mode of disintegrating.

The _Rapid_ is caused by the river struggling through a chasm bounded by two perpendicular walls of sandstone, over an uneven bed of the same material. On escaping from this narrow passage, it winds round the end of a lofty cliff of limestone, which forms part of a ridge that is continued through the country on both sides of the river.

Viewed from the summit of this ridge, which rises about eight hundred feet above the river, the country towards Bear Lake appears level. The view down the river presents also a plain country, bounded on the Mackenzie by another limestone ridge, which, unless the eye was deceived by the distance, gradually inclined to the one at the rapid, and appeared, by joining it to the northward, to form a great basin. These ridges are also prolonged to the southward. The plain is covered with wood, intersected by chains of lakes, and seemed to lie rather below the summit level of the banks of Bear Lake River. It is only comparatively, that the country deserves the name of plain, for its surface is much varied by depressions, ravines, and small eminences, that do not, however, destroy the general level appearance when seen from a distance. The view from the hill is terminated, to the westward, by the distant chain of the Rocky Mountains, running nearly N.W. by N. A little below the rapid, a small stream from the southward flows into the Bear Lake River, near whose sources the Indians procure an excellent common salt, which is deposited from the springs by spontaneous evaporation.

The walls of the rapid are about three miles long, and 120 feet high. [Sidenote: 25] They are composed of horizontal beds, the lower of which consist of an earthy-looking stone, intermediate between slate-clay and sandstone, having interiorly a dull yellowish-gray colour. Concretions, with smooth surfaces, about the thickness of a swan's quill, pass perpendicularly through the beds like pins, are prolonged beyond the partings, and bear some resemblance to portions of the roots or branches of a tree. The seam surfaces are very uneven. [Sidenote: 18] These beds are parted by thin, slaty layers, of a stone similar in appearance, but rather harder, and containing many interspersed scales of mica, and also some minute portions of carbonaceous matter in the form of lignite. [Sidenotes: 19, 1827] The thin layers contain impressions of ferns, and from the debris at the bottom of the cliff I gathered impressions of the bark of a tree (lepidodendron) and some ammonites in a brown iron-shot sandstone.[25] [Sidenote: 18, 20, 21, 22, 23, 24, 26, 27, 28] The upper beds are composed of a fine grained, quartzose, gray sandstone, having an earthy basis, and occasionally interspersed carbonaceous matter. Some of the beds are a foot and a half thick, and have sufficient tenacity to be fitted for making grindstones; most of the sandstone is, however, rather friable. Near the summit there is interposed a bed of fine-grained dolomite, and a friable sandstone, which forms the crest of the cliff, and exhibits in its weathering battlement-shaped projections and pinnacles. [Sidenote: 29] Covering this sandstone, but not quite to the margin of the cliff, there is a layer of slaty limestone, having a bluish or blackish-gray colour, a dull fracture, and rather compact structure. [Sidenote: 30] In the lower beds of the cliff there are some globular and disk-shaped concretions, of an indurated iron-shot slate-clay, or poor clay-iron-stone, containing pyrites. They vary in magnitude from six inches to a foot and a half in diameter, and appear to be formed of concentric layers, which are rendered apparent by the weathering of the stone. The sandstones and shales of the rapid have a strong resemblance in appearance to those of the coal measures; but pitch-coal was not detected at this place. Several distinct concretions of indurated slate-clay, assuming the appearance termed _cone in cone_, were picked up among the boulders on the banks of Bear Lake River, some way below the rapid, but they were not traced to their parent beds. They effervesce with acids.

Between the walls of the rapid and the limestone ridge there is a piece of meadow-ground, having a soft, clayey soil, in which, near the base of the hill, a small rivulet flows to join the river. The bed of this rivulet presents accumulations of boulders of large size, arranged so as to form two terraces, the upper of which is considerably above the highest level either of the rivulet, or of Bear Lake River. The boulders consist of varieties of granite, gneiss, mica-slate with garnets, greenstone and porphyry. [Sidenote: 50] One of the porphyries is a beautiful stone, composed of hyacinth-red felspar, and irregular crystals of milky quartz, with a few specks of a dark green mineral, and very much resembles a rock which is not uncommon in the gneiss districts about Fort Enterprize. [Sidenotes: 45, 47, 50, 51, 49] Many of the boulders consist of conglomerates and sandstones that strongly resemble those of the old red sandstone formation, which forms the height of land between Dease Bay and Coppermine rivers. Also some flinty slates, mixed, in thin layers, with compact, yellowish limestone, and some pebbles of jasper interleaved with flinty slate.

The limestone ridge below the rapid stands on a narrow base, whose transverse diameter does not exceed a quarter of a mile. Its summits are generally conical, but very rugged and craggy; the highest peak I had an opportunity of visiting is about a mile from Bear Lake River, and it has been already stated to be estimated at eight hundred feet above that stream, or nine hundred and fifty above the sea. The general direction of the ridge is from S.E. by S. to N.W. by N., or nearly parallel to the great Rocky Mountain chain, and to the smaller ridges betwixt it and that chain. Its prolongation through the flat surrounding strata, to the southward of Bear Lake River, can be traced for at least forty miles, and it is visible at nearly an equal distance, as it runs through the still more level country to the northward; but here, as has been already said, it appears to incline towards the similar ridge which is cut by the Mackenzie, at the mouth of the Bear Lake River, and is about twenty-five miles to the W.S.W., in a direct line. That part of the ridge which I had an opportunity of visiting, consisted entirely of limestone, generally in thick beds. Its stratification was not very evident, and in my very cursory examination the general dip was not clearly ascertained. A precipitous cliff, four hundred feet high, facing the S.E., and washed by the Bear Lake River, presents strata, inclined to the S.W. at an angle of 45 degrees, which may be perhaps considered as the general dip; for the ridge on that side slopes down to the surrounding country at an angle of about 30 degrees or 40 degrees, while on the N.E. side it presents lofty precipices formed by the cropping out of the strata. [Sidenote: 39, 34] Many of the beds in this hill consisted of a blackish-gray fine grained limestone, intersected by veins of calc-spar; [Sidenotes: 40; 35, 36; 42, 43, 44] but several layers of gray and dark coloured dolomites, and some of a yellowish-gray _rauchwacke_, were interstratified with them, and the upper parts of the precipitous cliff, [Sidenote: 35, 36] and also of the highest peak, consisted of a calcareous breccia, containing rounded pieces of brown limestone, and angular fragments of chert; and the faces of some cliffs, on the N.E. side of the hill, were incrusted with a fine crystalline gypsum to the depth of from one to two feet.[26]

The banks of Bear Lake River below the rapid have a more gentle declivity than those above it, and they occasionally recede from the stream, so as to leave a grassy slope varying from a few yards to half a mile in breadth. The sections of these banks by torrents present only sand or clay; and the hollows of the ravines are lined with boulders principally of primitive rocks. No stone was observed _in situ_ from the rapid until we came to the junction of the river with the Mackenzie.

The Bear Lake River flows into the Mackenzie at a right angle, and on its north bank, at its mouth, there is a hill, which has been already noticed as forming part of a ridge visible from the one at the rapid, with which it probably unites to form a great basin. These two hills seem to belong to the same formation. [Sidenote: 61, 62, 60] The body of the hill consists of highly-inclined beds of blackish-gray limestone, with sparry veins, and of brownish-gray dolomite, which cannot be distinguished in hand specimens from that of the hill at the rapid. The superior beds are formed of a calcareous breccia.[27] [Sidenote: 57, 58, 59, 63, 64, 65] Associated with these strata, however, there are beds of limestone, highly charged with bitumen; and at the base of the hill there are beds of bituminous shale, some of which effervesce with acids, whilst others approach in hardness, and other characters, to flinty slate. These shaly beds were seen by Captain Franklin and Mr. Kendall in autumn 1825, and they also saw, at that time, some sulphureous springs and streams of mineral pitch issuing from the lower parts of the limestone strata: but the whole of them were hid by the height of the waters of the Mackenzie in the spring of 1826.[28] [Sidenote: 69, 66, 67, 68] The same cause prevented me from seeing some beds of lignite and sandstone, at the same place, of which Captain Franklin obtained specimens.

LIGNITE FORMATION.--MACKENZIE'S RIVER.

Having noticed the general features of this portion of the river, I have next to state, that the formation constituting its banks may be characterized as consisting of wood-coal in various states, alternating with beds of pipe-clay, potter's clay, which is sometimes bituminous, slate-clay, gravel, sand, and friable sandstones, and occasionally with porcelain earth. The strata are generally horizontal, and as many as four beds of lignite are exposed in some parts, the upper of which are above the level of the highest river-floods of the present day.

The _lignite_, when recently detached from the beds, is pretty compact, but soon splits into rhomboidal pieces, which again separate into slates more or less fine. It burns with a very fetid smell, somewhat resembling that of phosphorus, with little smoke or flame, leaving a brownish-red ash, not one-tenth of the original bulk of the coal. The blacksmith found it unfit for welding iron when used alone, but it answered when mixed with charcoal, although the stench it created was a great annoyance. [Sidenote: 48] Different beds, and even different parts of the same bed, presented specimens of the fibrous brown-coal, earth-coal, conchoidal brown-coal, and trapezoidal brown-coal of Jameson. Some of the pieces have the external appearance of compact bitumen, but they generally exhibit, in the cross fracture, the fibrous structure of wood in concentric layers, apparently much compressed. Other specimens have a strong external resemblance to charcoal in structure, colour, and lustre. A frequent form of the lignite is that of slate, of a dull, brownish-black colour, but yielding a shining streak. The slate is composed of fragments, resembling charred wood, united together by a paste of more comminuted woody matter, mixed, perhaps, with a small portion of clay. In the paste there are some transparent crystals of sulphate of lime, and occasionally some minute portions of a substance like resin. These shaly beds bear a strong resemblance to peat, not only in structure but also in the mode of burning, and in the light whitish ashes which are left. The external shape of stems or branches of trees, is best preserved in some fragments impregnated with slate-clay, and occasionally with siliceous matter, which occur imbedded in the coal. The bark of these pieces has been converted into lignite. Some of them exhibit knots, such as occur where a branch has decayed, and others represent the twists and contortions of wood of stunted growth. The lignite is generally penetrated by fibrous roots, probably _rhizomorpha_, which insinuate their ramifications into every crevice.

The beds of lignite appear to take fire spontaneously when exposed to the atmosphere. They were burning when Sir Alexander Mackenzie passed down the river in 1789, and have been on fire, in some part or other of the formation, ever since. In consequence of the destruction of the coal, large slips of the bank take place, and it is only where the debris has been washed away by the river that good sections are visible. The beds were on fire when we visited them, and the burnt clays, vitrified sand, agglutinated gravel, &c. gave many spots the appearance of an old brick-field.

[Sidenote: 81] The _gravel_ interstratified with the lignite, consists of smooth pebbles of Lydian stone, of flinty slate, of white quartz, of quartzose sandstone, and conglomerate, like the sandstones and conglomerates of the old red sandstone formation, of claystone, and of slate-clay, varying in size from a pea to that of an orange. The gravel is often intermixed with a little clay, which gives the bed sufficient tenacity to form cliffs, but does not prevent the pebbles from separating, in the attempt to break off hand specimens. It is seamed by thin layers of fine sand: beds of sandstone are of occasional occurrence.

_Potter's clay_ occurs in thick beds, has generally a gray or brown colour, and passes, in some places, into a highly bituminous thick-slaty clay, penetrated by ramifications of carbonaceous matter resembling the roots of vegetables.

The _pipe-clay_ is deserving of particular notice. It is found in beds from six inches to a foot thick, and mostly in contact with the lignite. It has commonly a yellowish-white colour, but in some places its hue is light lake-red. The natives use it as an article of food in times of scarcity and it is said to have sustained life for a considerable time. It is termed _white mud_ by the traders, who whitewash their houses with it. It occurs also in lignite deposits on the upper branches of the Saskatchewan, and is associated with bituminous shale on the coast of the Arctic Sea. Mr. Nuttall mentions a similar substance, under the name of pink-clay, as being found in the lignite deposits on the Arkansa.[29]

The _porcelain earth_ was observed only at one place where the beds were highly inclined, and there it appeared to replace the sandstones of other parts of the deposit. It has a whitish colour, and the appearance, at first sight, of chalk; but some of its beds, from the quantity of carbonaceous matter interspersed through them, having a grayish hue. Its beds are from two to three yards thick.

In a note[30] I have mentioned the most remarkable sections of this formation which occur on the banks of the Mackenzie. The depth of the formation was not ascertained, but the sections will show the thickness of the beds which were exposed. The height above the sea of the summit of the banks it forms on the Mackenzie, was estimated to be from two hundred and fifty to three hundred feet.

NOTICES OF OTHER LIGNITE FORMATIONS.

Similar formations of lignite occur near the foot of the Rocky Mountain range farther to the southward; but I have not, after many inquiries, heard of any traces of them in the eastern parts of the Hudson's Bay lands. Sir Alexander Mackenzie, after describing the general course of the Rocky Mountains, says that "along their eastern edge, there occurs a narrow strip of marshy, boggy, and uneven ground, which produces coal and bitumen;" and that "he saw these on the banks of the Mackenzie in lat. 66 degrees, and, in his second journey, on the Peace River, in lat. 56 degrees and 146 degrees W. long.;" and further, that "the same was observed by Mr. Fidler, on the south branch of the Saskatchewan, in lat. 52 degrees long. 112-1/2 degrees W." Mr. Alexander Stewart, an intelligent chief factor of the Hudson's Bay Company, and well acquainted with those countries, informs me that there are beds of coal on fire, on the Smoking River, or east branch of the Peace River, and on the upper parts of the _Riviere la biche_, or Elk River; and that coal, although not on fire, occurs at Lesser Slave Lake, on a line with the other two localities. Mr. Small, a clerk to the Hudson's Bay Company, likewise acquaints me, that coal occurs at Edmonton, on the north branch of the Saskatchewan, in beds, sometimes seven or eight feet thick. Most of the coal is thin-slaty; but some beds yield shining, thick lumps, which break, as he expresses it, like Spanish liquorice. It lies over beds of bluish-gray sandstone, and is associated with a white clay, which froths in water and adheres to the fingers.

Mr. Drummond brought specimens from the spot which Mr. Small alludes to and remarks, that the lignite occurs in beds from six inches to two feet thick, separated by clay and sandstones. [Sidenote: 1051, 1052, 1053] His specimens of the lignite are precisely similar to the slaty and conchoidal varieties, which occur at the mouth of the Bear Lake River; [Sidenote: 1055] and there is an equal resemblance betwixt the sandstones from the two places. [Sidenote: 1053] The slaty beds of lignite, at Edmonton, pass into a thin, slaty, friable sandstone, much impregnated by carbonaceous matter, and containing pieces of fibrous lignite. [Sidenote: 1056, 1062] In the neighbourhood of the lignite there are some beds of rather indurated, but highly bituminous shale, and the clayey banks contain clay-iron stones, in form of septaria. Mr. Drummond likewise found beds of a beautiful bituminous coal, which Professor Buckland, from its peculiar fracture, considers to be tertiary pitch-coal. [Sidenote: 1058, 1059, 1060] The banks of the Saskatchewan, near the same place, exhibit beds of a very compact stone, having a brown colour, and inclosing many fragments of bituminous limestone and some organic remains; likewise beds of a somewhat similar stone, but full of drusy cavities, and more resembling a recent calcareous tufa. I could not learn how far these beds were connected with the lignite deposit.

Captain Franklin[31] saw beds of lignite and tertiary pitch-coal at Garry's Island, off the mouth of the Mackenzie, and there is an extensive deposit of it near the Babbage River, on the coast of the Arctic Sea, opposite to the termination of the Richardson chain of the Rocky Mountains.

MACKENZIE RIVER FROM SLAVE LAKE TO THE BASE OF THE ROCKY MOUNTAINS.

Having now described the strata in Bear Lake River, together with the exposed beds of the lignite at its mouth, as far as opportunities of observation enable me, and also added a slight account of similar formations which occupy a like situation at the foot of the Rocky Mountain range, were I to adapt the order of my notices strictly to the route of the expedition, I should next describe the banks of the Mackenzie from the junction of the Bear Lake River downwards to the Arctic Sea. It seems, however, more advisable to commence at the origin of the Mackenzie, in Great Slave Lake, and give as connected a view as I can of the principal geological features of that great river.

The west end of Slave Lake is bounded by horizontal strata of a limestone, whose characters shall be afterwards given in detail; and I have merely to remark, at present, that it forms flat shores, which are skirted by shoals of boulders of limestone, and of primitive rocks. Much drift timber is accumulated in the small bays at this end of the lake, which, in process of time, is converted into a substance like peat. A chain of islands extends obliquely across the lake at the origin of the river, or where the current is first felt; and the depth of the water there is less than six feet. Below this, there is a dilatation termed the _first little lake_, and the river afterwards contracts to less than a mile in breadth; forming in one place, when the water is low, a strong rapid. A second dilatation, about twenty-five miles below the first, is termed the _second little lake_. The shores throughout this distance are generally flat and covered with boulders of limestone, compact felspar, granite, gneiss, and sienite, and there are many of these stones imbedded in a tenacious clay, which forms the beach. A ridge, having an even outline, and apparently of small elevation, commences behind Stony Point, in Slave Lake, some distance inland, and, running nearly parallel to the river, disappears about Fishing River, a stream which joins the Mackenzie, below the Second Little Lake. The Horn Mountains, a ridge of hills, of considerably greater elevation, and having a more varied outline than that on the south shore, are first visible on the north side of the Second Little Lake, and continue in sight nearly as far as the junction of the "River of the Mountains," or "Forks, of the Mackenzie," as the traders term the union of the two rivers. [Sidenote: 120, 121] The only rocks seen _in situ_ between Slave Lake and the Forks, were a bituminous shale of a brownish-black colour, in thin slates, and a slate-clay of a pure yellowish-gray colour, which, as well as the bituminous shale, forms steep banks.

ROCKY MOUNTAINS.

About twenty-five or thirty miles below the forks, the first view is obtained of the Rocky Mountains, which there appear to consist of short-conical peaks, scarcely rising two thousand feet above the river. Some distance lower down, the river, changing its course from W.N.W. to N.N.E., turns sharply round the mountains, which are there disposed in ridges, having bases from one to two miles wide, and a direction of S.S.W. or S.W. by S. being nearly at right angles to the general course of the great range to which they belong. The eastern sides of the ridges present a succession of wall-sided precipices, having beneath them shelving acclivities formed by debris, and exhibiting on their faces regular lines of stratification. The western sides of the ridges are of more easy ascent. The vallies which separate these ridges and open successively to the river, are narrow, with pretty level bottoms, but very steep sides well clothed with trees. In the first ridge, the strata seemed to dip to the northward at an angle of 35 degrees. In some of the others they were horizontal, or had a southerly dip. The third ridge presents, when viewed from the westward, a magnificent precipice, seemingly about one thousand two hundred feet high, and which extends for at least fifteen miles. After passing this ridge, the river inclines to the eastward, and the forms of the hills are less distinctly seen.

As I could not visit the Rocky Mountains, I know nothing of their structure except from report. An interpreter in the Hudson's Bay Company's service, who had travelled over them, informed me that there are fourteen or fifteen ridges, of which the three easternmost are the most rugged, those that succeed being broader and more rounded. [Sidenote: 122] This man gave me a specimen of a pearl-gray semi-opal, resembling obsidian, brought from the third or fourth ridge. The natives, by means of fire, cause this stone to break off in thin, flat, conchoidal fragments, with which they form arrow-heads and knives. The thin pieces are nearly transparent on the edges. [Sidenote: 123] He also gave me a specimen of plumbago, from the same quarter, and some specular iron.

Mr. Macpherson, of the Hudson's Bay Company, in a letter respecting the Rocky Mountains, near _Fort au Liard_, on the River of the Mountains, or south branch of the Mackenzie, informs me, that "these mountains may be traced into somewhat uniform ranges, extending north-westerly and south-easterly, nearly parallel with the River of the Mountains, and are in appearance confusedly scattered and broken, rising here and there into high peaks." [Sidenote: 124, 125] This gentleman had the kindness to send me specimens of a cherty rock, some of which, he states, were from the third range westward from the river, and others from a spur which projects in a southern direction from the fourth range, and rises about six hundred feet above the adjacent valley. These specimens cannot be distinguished from those of Limestone Point, on the north shore of Great Bear Lake[32], Mounts Fitton and Conybeare, two remarkable peaks which terminate the Eastern range of the Rocky Mountains on the shores of the Arctic sea, were found by Captain Franklin to consist of transition rocks, of which an account is given in the subjoined note.[33]

Sir Alexander Mackenzie, towards the conclusion of the interesting narrative of his voyages, says, of the Rocky Mountain range, "The last line of division is, the immense ridge, or succession of ridges of the stony mountains, whose northern extremity dips in the Arctic Sea in latitude 70 degrees north, and longitude 135 degrees west, running nearly south-east, and begins to be parallel to the coast of the Pacific ocean from Cook's inlet, and so onwards to the Columbia. From thence it appears to quit the coast, but still continuing with less elevation to divide the waters of the Atlantic from those of the Pacific. In these snow-clad mountains rises the Mississippi, if we admit the Missouri to be its source, which flows into the Gulph of Mexico; the river Nelson which is lost in Hudson's Bay; Mackenzie's river that discharges itself into the North Sea, and the Columbia emptying itself into the Pacific Ocean. The breadth of the mountains from Cook's inlet to the Columbia is from four to eight degrees easterly." I may add, that the great rivers mentioned by Mackenzie not only take their origin from the same range of mountains, but almost from the same hill; the head waters of the Columbia and Mackenzie being only about two hundred yards apart in latitude 54-1/2 degrees. Mr. Drummond, who crossed the mountains at that place, informs me, that the Eastern side of the range consists of conglomerate and sandstone, to which succeed limestone hills exceedingly barren, and afterwards clay-slate and granite.

James, the intelligent naturalist, who accompanied Major Long on his first expedition, says of the Rocky Mountains to the southward of the Missouri, "They rise abruptly out of the plains which lie extended at their base on the east side, towering into peaks of great height, which renders them visible at the distance of more than one hundred miles from their base. They consist of ridges, knobs, and peaks, variously disposed, among which are interspersed many broad and fertile valleys. James's peak, one of the more elevated, was ascertained by trigonometrical measurement to rise 8500 feet above the common level. The rocky formations are uniformly of a primitive character, but a deep crust of secondary rocks appears to recline on the east side of the mountains, extending upwards from their base many hundred feet." In another place, he says, "The woodless plain is terminated by a range of naked and almost perpendicular rocks, visible at the distance of several miles, and resembling a vast wall parallel to the base of the mountain. These rocks are sandstone, and rise abruptly to an elevation of one hundred and fifty or two hundred feet." The sandstone walls seem to present an appearance not very dissimilar to some of the cliffs seen from the Mackenzie.

Having thus mentioned as briefly as I could the extent of the information I was able to collect, respecting the Rocky Mountain range, I may remark, that a formation of primitive rocks, but little elevated above the general level of the country, appears to run from near the west end of Lake Superior, gradually and slightly converging towards the Rocky Mountains, until it attains the east side of Great Bear Lake. In lat. 50 degrees, the two ranges are nearly seven hundred miles apart, and there, and as far as lat. 60 degrees, the space between them is principally occupied by horizontal strata of limestone. There is also much limestone in the narrower interval north of 60 degrees, but the strata are more inclined, and form abrupt hills and ridges, particularly about lat. 66 degrees, where the primitive rocks on the east of Bear Lake are within two hundred miles of the Rocky Mountains. Sir Alexander Mackenzie has noticed that a chain of great lakes skirts this eastern range of primitive rocks, where they are approached by the flat limestone strata which lie to west of them. Thus the primitive rocks bound Great Slave Lake to the eastward of Slave River, and the flat limestone strata occupy the country westward of that lake, as has been already mentioned.

After this digression, which seemed necessary for the purpose of giving a general idea of the structure of the country, I return to the description of the banks of the Mackenzie.

MACKENZIE RIVER FROM THE FIRST SIGHT OF THE ROCKY MOUNTAINS TO BEAR LAKE RIVER.

At the sharp turn of the river round the Rocky Mountains, its east bank swells gently into a hill several feet high. Below this the banks are broken into conical masses by ravines, and present a finely variegated outline. A pretty high ridge, looking like a continuation of the Horn Mountains, is visible on the east side some distance inland. Opposite to the Big Island there is a green hill three or four hundred feet high, which, as we descended the river, showed itself to be part of a range that had a direction apparently to the N.N.W., and towards its northern end became more rugged and craggy, exhibiting cliffs and rude embrasures, at the same time increasing in height to eight hundred or one thousand feet. The boulders on the beach change their character considerably about this place. Farther up, the yellowish-white limestone which occurs in Slave Lake formed a great portion of them; but here a greenish-gray, and rather dark-coloured, compact limestone, with a flat conchoidal fracture, replaces it. Variegated-sandstone, and some purplish, felspathose-sandstone, or compact felspar, also occur pretty frequently, together with slaty limestone, bituminous-shale, lydian-stone, pitchstone-porphyry, and various sienites, granites, and greenstones, almost all porphyritic.