At dawn (September 16), I began the short march leading to the Yellala.[29] By stepping a few paces south of Nkulu, we had a fine view of the Borongwa ya Vivi, the lowest rapids, whose foaming slope contrasted well with the broad, smooth basin beyond. Palabala, the village of Nekorado on the other side of the stream, bore south (Mag.), still serving as a landmark; and in this direction the ridges were crowned with palm orchards and settlements. But the great Yellala was hidden by the hill- shoulder.
We at once fell into a descent of some 890 feet, which occupied an hour. The ground was red iron-clay, greasy and slippery; dew- dripping grass, twelve to fifteen feet tall, lined the path; the surface was studded with dark ant-hills of the mushroom shape; short sycomores appeared, and presently we came to rough gradients of stone, which severely tried the "jarrets." After an hour, we crossed at the trough-foot a brook of pure water, which, uniting with two others, turns to the north-east, and, tumbling over a little ledge, discharges itself into the main drain. An ascent then led over a rounded hill with level summit, and precipitous face all steps and drops of rock, some of them six and seven feet high, opposed to the stream. Another half hour, and a descent of 127 feet placed us under a stunted calabash, 100 feet above the water, and commanding a full view of the Yellala.
On the whole, the impression was favourable. Old Shimbah, the Linguister at Porto da Lenha, and other natives had assured me that the Cataracts were taller than the tallest trees. On the other hand, the plain and unadorned narrative of the "Expedition" had prepared me for a second-rate stream bubbling over a strong bed. The river here sweeps round from the north-west, and bends with a sharp elbow first to the south-west and then to the south- east, the length of the latter reach being between four and five miles. As far as the eye can see, the bed, which narrows from 900 to 400 and 500 yards, is broken by rocks and reefs. A gate at the upper end pours over its lintel a clear but dwarf fall, perhaps two feet high. The eastern staple rises at first sheer from the water's edge to the estimated altitude of a thousand feet,—this is the "Crocodile's Head" which we saw on the last march, and already the thin rains are robing its rocky surface with tender green. The strata are disposed at angles, varying from 35° to 45°, and three streaks of bright trees denote Fiumaras about to be filled. Opposite it is the "Quoin Hill," bluff to the stream, and falling west with gradual incline. The noise of this higher fall can hardly be heard at Nkulu, except on the stillest nights.
Below the upper gate, the bed, now narrowing to 300 yards, shows the great Yellala; the waters, after breaking into waves for a mile and a half above, rush down an inclined plane of some thirty feet in 300 yards, spuming, colliding and throwing up foam, which looks dingy white against the dull yellow-brown of the less disturbed channel—the movement is that of waves dashing upon a pier. The bed is broken by the Zunga chya Malemba, which some pronounced Sanga chya Malemba, an oval islet in mid-stream, whose greater diameter is disposed along the axis of the bed. The north-western apex, raised about fifty feet above the present level of the waters, shows a little bay of pure sand, the detritus of its rocks, with a flood-mark fifteen feet high, whilst the opposite side bears a few wind-wrung trees. The materials are gneiss and schist, banded with quartz—Tuckey's great masses of slate. This is the "Terrapin" of the Nzadi. The eastern fork, about 150 yards broad, is a mountain-torrent, coursing unobstructed down its sandy trough, and, viewed from an eminence, the waters of the mid-channel appear convex, a shallow section of a cylinder,—it is a familiar shape well marked upon the St. Lawrence Rapids. The western half is traversed by a reef, connecting the islets with the right bank. During August, this branch was found almost dry; in mid-September, it was nearly full, and here the water breaks with the greatest violence. The right bank is subtended for some hundred yards by blocks of granite and greenstone, pitted with large basins and pot-holes, delicately rounded, turned as with a lathe by the turbid waters. The people declare that this greenstone contains copper, and Professor Smith found particles in his specimens. The Portuguese agents, to whom the natives carefully submit everything curious, doubt the fact, as well as all reports of gold; yet there is no reason why the latter should not be found.
The current whirls and winds through its tortuous channels, which are like castings of metal, in many distinct flows; some places are almost stagnant, suggesting passages for canoes. Here the fishermen have planted their weirs; some are wading in the pools, others are drying their nets upon the stony ledges. During the floods, however, this cheval-de-frise of boulders must all be under water, and probably impassable. Tuckey supposes that the inundation must produce a spectacle which justifies the high- flown description of the people. I should imagine the reverse to be the case; and Dr. Livingstone justly remarked [30] that, when the river was full, the Yellala rapids would become comparatively smooth, as he had found those of the Zambeze; and that therefore a voyage pittoresque up the Congo should be made at that season.
Before leaving the Yellala, I wandered along the right bank, and found a cliff, whose overhanging brow formed a fine cavern; it remarkably resembled the Martianez Fountain under the rock near the beautiful Puerto de Orotava. Here the fishermen were disporting themselves, and cooking their game, which they willingly exchanged for beads. All were of the Silurus family, varying from a few inches to two feet. Fish-eagles sat upon the ledges overhanging the stream, and a flight of large cranes wheeled majestically in the upper air: according to the people, they are always to be seen at the Yellalas.
The extent of a few hundred feet afforded a good bird's eye view of the scene. The old river-valley, shown by the scarp of the rocks, must have presented gigantic features, and the height of the trough-walls, at least a thousand feet, gives the Yellala a certain beauty and grandeur. The site is apparently the highest axis of the dividing ridge separating the maritime lowlands from the inner plateau. Looking eastward the land smoothens, the dorsa fall more gently towards the counter-slope, and there are none of the "Morros" which we have traversed.
With the members of the Congo Expedition, I was somewhat startled by the contrast between the apparently shrunken volume of waters and the vast breadth of the lower river; hence Professor Smith's theory of underground caverns and communications, in fact of a subterraneous river, a favourite hobby in those days. But there is not a trace of limestone formation around, nor is there the hollow echo which inevitably would result from such a tunnel. Evidently the difference is to be accounted for by the rapidity of the torrent, the effect of abnormal slope deceiving the eye. At the Mosî-wa-tunya Falls the gigantic Zambeze, from a breadth of a thousand yards suddenly plunges into a trough only forty- five to sixty feet wide: the same is the case with the Brazilian São Francisco, which, a mile wide above the Cachoeira de Paulo Affonso, is choked to a minimum breadth of fifty-one feet. At the Pongo (narrows) de Manseriche also, the Amazonas, "already a noble river, is contracted at its narrowest part to a width of only twenty-five toises, bounded on each margin by lofty perpendicular cliffs, at the end of which the Andes are fairly passed, and the river emerges on the great plain."[31] Thus the Yellala belongs to the class of obstructed rapids like those of the Nile, compared with the unobstructed, of which a fine specimen is the St. Lawrence. It reminded me strongly of the Búsa (Boussa) described by Richard Lander, where the breadth of the Niger is reduced to a stone-throw, and the stream is broken by black rugged rocks arising from mid-channel. It is probably a less marked feature than the Congo, for in June, after the "Malka" or fourteen days of incessant rain, the author speaks of whirlpools, not of a regular break.
I thus make the distance of the Yellala from the mouth between 116 and 117 miles and the total fall 390 feet, of which about one half (195) occurs in the sixty-four miles between Boma and the Yellala: of this figure again 100 feet belong to the section of five miles between the Vivi and the Great Rapids. The Zambeze, according to Dr. Livingstone ("First Expedition," p. 284), has a steeper declivity than some other great rivers, reaching even 7 inches per mile. With 3 to 4 inches, the Ganges, the Amazonas, and the Mississippi flow at the rate of three knots an hour in the lowest season and five or six during the flood: what, then, may be expected from the Nzadi?
According to the people, beyond the small upper fall where projections shut out the view, the channel smoothens for a short space and carries canoes. Native travellers from Nkulu usually take the mountain-path cutting across an easterly bend of the bed to Banza Menzi, the Manzy of Tuckey's text and the Menzi Macooloo of his map. It is situated on a level platform 9 miles north of Nkulu, and they find the stream still violent. The second march is to Banza Ninga, by the First Expedition called "Inga," an indirect line of five hours = 15 miles. The third, of about the same distance, makes Banza Mavunda where, 20 to 24 miles above the Yellala, Tuckey found the river once more navigable, clear in the middle and flowing at the rate of two miles an hour—a retardation evidently caused by the rapids beyond: I have remarked this effect in the Brazilian "Cachoeiras."[32] Above it the Nzadi widens, and canoeing is practicable with portages at the two Sangallas. The southern feature, double like the Yellala, shows an upper and a lower break, separated by two miles, the rapids being formed as usual by sunken ledges of rock. Two days' paddling lead to the northern or highest Sangalla, which obstructs the stream for 22 miles: Tuckey (p. 184) makes his Songo Sangalla contain three rapids; Prof. Smith, whose topography is painfully vague, doubles the number, at the same time he makes Sanga Jalala (p. 327) the "uppermost fall but one and the highest." Finally, at Nsundi (on the map Soondy N'sanga), which was reached on Sept. 9, a picturesque sandy cove at the opening of a creek behind along projecting point, begins a lake- like river, three miles broad, with fine open country on both banks: the explorer describes it as "beautiful scenery equal to anything on the banks of the Thames."