The Physical Features of the Congo.
Roughly we may describe the Basin of the Congo as extending from the
5th degree of North, to the 12th degree of South, latitude, and from
the hills skirting the coast of the Atlantic Ocean to 31st or 32nd
degree of East longitude.
Along what is known as the South-West Coast of Africa, from the Gulf
of Biafra southwards, stretches a ridge of hill country. It commences
about fifty to seventy miles inland, and is about 300 miles in width.
In some parts it attains an elevation of 5,000 or more feet, but the
general altitude near the Congo is from 2,000 to 2,500 above the level
of the sea. It is really a belt or elevated plateau; rich soil is to be
found on the summits of the ‘hills,’ but the whole has been torn and
worn by the rains; little streams have in time cut out deep gorges, the
sides of which are being further eroded, until what was once a rolling
table-land appears as a chaos of hills; only from a few heights can
one gain a fair idea of the nature of the country.
This plateau belt forms the western watershed of the Congo River, and
on its seaward slopes gives rise to many unimportant streams, of which
the Cameroons, Gaboon, Ogowai, Kwilu, Chiloango, Mbidiji, (Ambrize),
Loje, and Kwanza are the principal. The Ogowai is the most important,
and has been explored by M. de Brazza for the French Government, which
has now annexed its entire basin. It is navigable for some 150 miles
for vessels of light draught; but beyond its course is much impeded by
cataracts.
This water-torn plateau country, with its little useless rivers, has
presented a formidable obstacle to exploration, and has served to throw
all interior water into the Congo. To the north of the Great Basin
stretches the high lands of the unknown countries which form also
the watershed of the Shari and the Nile. Eastward stretches the hill
country on the west of the Victoria and Albert Nyanza, and on the east
of Tanganika, while to the south is the watershed of the Zambesi.
This great circle of hills probably enclosed at one time an immense
fresh-water lake, of an area of a million and a half square miles,
which at length, overflowing at its weakest point, formed the outlet
which we to-day call the Congo River. The immense flood thus released
tore out the deep gorge, which is now 1,000 and 1,500 feet below the
main level. There are signs in some parts of changes in its course, one
notably in the Bundi valley, thirty-five miles from Vivi, which was at
one time undoubtedly a channel of the Congo; there are other valleys
also presenting that appearance, the levels, entrances, and exits of
which would lead one to conclude that such had been the case.
If a transverse section were taken about the middle of the cataract
region, there would be first an ascent from the river, almost
perpendicular, of from 300 to 500 feet in about one-third of a mile,
then a much steadier rise of some 500 to 700 feet in two miles, and
then a rise of another 500 to 700 feet in eight miles, with a further
steady rise for five miles, so that the actual valley in the cataract
region might be estimated roughly at from twenty to thirty miles in
breadth. The river itself varies from 300 yards to one-and-a-half or
two miles wide at mid-flood; while the difference between the highest
water of the rainy season and the lowest in the dry season, varies from
forty feet in the worst parts to about three feet on the lower river.
To the geologist the country between the coast and Stanley Pool is
best studied along the river. The first low hills approach near to the
mouth of the river, which is about seven miles wide, and devoid of a
delta; the next step in the plateau occurs at five miles west of Mboma,
fifty miles from the coast, where the tops of the ‘hills’ are from 500
to 700 feet in height. There we find a red clay yielding copal above
granitic rocks. The banks grow steeper and the river narrows, until at
Vivi the first serious obstacle is met, the plateau level being about
1,700 feet, and the river about 600 yards wide. Just above this is
the fierce Yelala Cataract; indeed, nowhere can you properly speak of
falls; a drop of fifty feet, which would be a fine scene on an ordinary
river, is almost disregarded by the Congo. The bed of a cataract must
be of very hard rock, and down this inclined plane, the river, nipped
tightly by the hills, rushes with fearful velocity, leaping in mad
waves, foaming and raging at its rocky obstacles. In some of the milder
cataracts it rushes down a swirling mound of water, which projected
into the quieter low level at the foot of the cataract, races on as
a heap of waters for nearly half a mile, before it consents to swirl
about at the lower level. Fierce up currents run along the shore at
such points, which would draw boats or canoes into the swirling
current, while along the edges of these counter-currents are great
whirlpools, giving way to each other, disappearing, and breaking up
into ‘caldrons,’ the whole surface heaving and seething. In a creek
three miles below the Ntombo Cataract we have watched this heaving. The
water would flow outwards from the creek, then meeting the impulse of a
fresh heave, would flow back until it would remain stationary for some
twenty seconds, often two feet higher than what it was a minute ago.
This flows backwards and forwards in the creek, recurring every two
minutes or minute and a half.
[Illustration: A LOAD.]
At Vivi the country is much eroded, granitic rocks, schist, mica,
gneiss, and quartz are exposed. The hill-sides are rock strewn, and
the country is wild and desolate, covered with weak grass and stunted
gnarled trees. In the more level spots rich soil has collected, and the
natives cultivate there their cassava, ground-nuts, etc. This is the
nature of the country for the next fifty miles. Near the river a chaos
of hills, further away rolling plateau, covered with strong grass and
stunted trees. The tops of these _nzanza_, by Mr. Stanley’s careful
survey, vary but fifty feet over stretches of forty miles. Above
Isangila limestone crops up with slaty rocks, the main level near
the river is lower, and traversed by straight ridges of hills running
parallel with the coast, and from five to ten miles apart. Clear of the
limestone, the country is once more a torn plateau, slate and shale
abound, until at 200 miles from the coast occurs a very marked step of
700 feet. Here the country is from 2,300 to 2,500 feet above the sea,
and continues so, the rock being a red or purple sandstone. Several
higher ridges cross the country as you near Stanley Pool, cut abruptly
by the gorge of the river, and continued on beyond. Stanley Pool is a
widening out of the river in a weak point among the hills, which marks
the head of the cataract region, the water level being about 1,000 feet
above the sea. The plateau country continues for a further 150 miles,
when hills disappear, and the main level appears to be about 1,100
feet above the sea. From Irebu, 250 miles above the Pool, to Stanley
Falls, the banks are forest-clad. The country then divides itself into
three regions between the coast and Stanley Falls. The lower river 100
miles, cataract region 200 miles (nearly 300 miles in winding course),
the upper river 1,060 miles. Or coast level fifty miles, plateau level
400 miles, central level 900 miles, of which 800 miles are forest-clad
banks.
The cataract region is the obstacle that has kept so long secret this
great highway; but that passed, on the upper river there are 1,100
miles of unimpeded navigation, while the affluents are estimated at
2,000 miles; beyond the Stanley Falls stretch another 2,000 miles of
riverway. Two of the affluents have been explored, and on each was
found a lake, while the natives at the mouths of other affluents speak
of lakes. It is highly probable that further explorations will reveal
other lake regions, all available to the steamers and boats on the
upper river.
Communications interiorwards are certain; but between the coast and
Stanley Pool everything must be transported on men’s heads, until there
shall be a railway. The roads are mere footpaths over the hills from
town to town; while the tall thick grass is so strong that it must be
hoed up and the bushes cleared before any wheeled carriage could be
used. Then again the country is so torn, and streams in their deep
gorges so abundant, that travelling is very largely a series of ascents
and descents.