Chapter IX. Up the Congo to Banza Nokki.
For a wonder the canoes came in time, and, despite their mat- sails, we could not complain of them. There were twelve paddlers two for the stem, and two for the stern of each craft, under a couple of interpreters, Jotakwassi and Nchama-Chamvu, who were habited in European frock-coats of broadcloth, and in native terminations mostly "buff." Our excellent host bade us a kindly adieu, with many auguries of success - during the last night the frogs had made a noise in the house. Briefly, we set out on September 6th.
In the forty-five miles between Boma, where we enter the true trough of the Congo, and the landing-place of Banza Nokki below the cataracts, there are half-a-dozen reaches, the shortest of three, the longest of fifteen miles. They are not straight, as upon the chart; the windings of the bed exclude direct vision, and the succession of points and bays suggest, like parts of the Rhine, a series of mountain-tarns. The banks show the high-water level in a low shelf, a ribbon of green, backed by high rolling hills, rounded and stony, with grass dry at this season; the formation is primitive, and the material of the lower bed has been held to "prove the probability that the mountains of Pernambuco, Rio de Janeiro, and other adjacent parts of South America, were primevally connected with the opposite chains, that traverse the plains of Congo and Loango." In parts the rocks fall bluff into the river, and here the current rushes past like a mill-race without a shadow of backwater. The heights are intersected by gullies and ravines, of which I counted sixty-nine on the right and fifty-four on the left bank; many of them are well wooded, and others are fronted by plains of the reeds and flags, which manufacture floating islands, cast loose, like those of the Niger, about the end of July by the "Malka" rains. About a dozen contained running water: Captain Tuckey did not see one that would turn a mill in August and September; but in November and December all these fiumaras will discharge torrents.
The breadth of the entroughed bed varies from 700 yards to two miles where it most dispreads itself. The current increases from the normal three to five knots in rare places; the surface loses the glassiness of the lower section, and at once shows the boiling and swirling which will be noticed near the cataracts. The shores are often foul, but the midway is mostly clear, and, where sunken rocks are, they are shown by whirlpools. The flow of the tide, or rather the damming up of the lower waters between Porto da Lenha and the mouth, causes a daily rise, which we found to measure about a foot; thus it assists in forming a treble current, the rapid down-flow in the Thalweg being subtended by a strong backwater on either side carrying a considerable portion in a retrograde direction, and showing a sensible reflux; this will continue as far as the rapids. In the Amazonas the tides are felt a hundred leagues from the mouth; and, whilst the stream moves seawards, the level of the water rises, proving an evident under-current. Mr. Bates has detected the influence of oceanic tides at a point on the Tapajos, 530 miles distant from its mouth, such is the amazing flatness of the country's profile: here we find the reverse.
The riverine trough acts as wind-conductor to a strong and even violent sea-breeze; on the lower section it begins as a ground- current - if the "bull" be allowed - a thin horizontal stratum near the water, it gradually curves and slides upwards as it meets the mountain flanks, forming an inverted arch, and extending some 2,000 to 3,000 feet above the summits. At this season it is a late riser, often appearing about 3 P.M., and sometimes its strength is not exhausted before midnight. The brown water, grass-sheeted at the sides, conceals the bright yellow sand of the bed; when placed in a tumbler it looks clear and colourless, and the taste is perfectly sweet - brackishness does not extend far above Porto da Lenha. Yet at Boma the residents prefer a spring near the factories, and attribute dysentery to the use of river-water. According to Mr. George Maxwell, the supply of the lower bed has the quality of rotting cables, and the same peculiarity was attributed to the Tanganyika.
Of late years no ship has ventured above Boma, and boats have ascended with some difficulty, owing to the "buffing stream." Yet there is no reason why the waters should not be navigated, as proposed in 1816, by small steamers of good power, and the strong sea-breeze would greatly facilitate the passage. In older and more enterprising days merchant-schooners were run high up the Zaire. The master of a vessel stated to Tuckey that he "had been several voyages up to the distance of 140 miles from the mouth" without finding any difficulty.