Africa

Africa

AFRICA

AFRICA, the name of a continent representing the largest of the three

great southward projections from the main mass of the earth's surface. It

includes within its remarkably regular outline an area, according to the

most recent computations, of 11,262,000 sq. m., excluding the islands.1

Separated from Europe by the Mediterranean Sea, it is joined to Asia at its

N.E. extremity by the Isthmus of Suez, 80 m. wide. From the most northerly

point, Ras ben Sakka, a little west of Cape Blanc, in 37 deg. 21' N., to

the most southerly point, Cape Agulhas, 34 deg. 51' 15'' S., is a distance

approximately of 5000 m.; from Cape Verde, 17 deg. 33' 22'' W., the

westernmost point, to Ras Hafun, 51 deg. 27' 52'' E., the most easterly

projection, is a distance (also approximately) of 4600 m. The length of

coast-line is 16,100 m. and the absence of deep indentations of the shore

is shown by the fact that Europe, which covers only 3,760,000 sq. m., has a

coast-line of 19,800 m.

I. PHYSICAL GEOGRAPHY

The main structural lines of the continent show both the east-to-west

direction characteristic, at least in the eastern hemisphere, of the more

northern parts of the world, and the north-to-south direction seen in the

southern peninsulas. Africa is thus composed of two segments at right

angles, the northern running from east to west, the southern from north to

south, the subordinate lines corresponding in the main to these two

directions.

Main Geographical Features.—The mean elevation of the continent

approximates closely to 2000 ft., which is roughly the elevation of both

North and South America, but is considerably less than that of Asia (3117

ft.). In contrast with the other continents it is marked by the

comparatively small area both of very high and of very low ground, lands

under 600 ft. occupying an unusually small part of the surface; while not

only are the highest elevations inferior to those of Asia and South

America, but the area of land over 10,000 ft. is also quite insignificant,

being represented almost entirely by individual peaks and mountain ranges.

Moderately elevated tablelands are thus the characteristic feature of the

continent, though the surface of these is broken by higher peaks and

ridges. (So prevalent are these isolated peaks and ridges that a special

term [Inselberg-landschaft] has been adopted in Germany to describe this

kind of country, which is thought to be in great part the result of wind

action.) As a general rule, the higher tablelands lie to the east and

south, while a progressive diminution in altitude towards the west and

north is observable. Apart from the lowlands and the Atlas range, the

continent may be divided into two regions of higher and lower plateaus, the

dividing line (somewhat concave to the north-west) running from the middle

of the Red Sea to about 6 deg. S. on the west coast. We thus obtain the

following four main divisions of the continent:—-(1) The coast plains—-

often fringed seawards by mangrove swamps—never stretching far from the

coast, except on the lower courses of streams. Recent alluvial flats are

found chiefly in the delta of the more important rivers. Elsewhere the

coast lowlands merely form the lowest steps of the system of terraces which

constitutes the ascent to the inner plateaus. (2) The Atlas range, which,

orographically, is distinct from the rest of the continent, being

unconnected with any other area of high ground, and separated from the rest

of the continent on the south by a depressed and desert area (the Sahara),

in places below sea-level. (3) The high southern and eastern plateaus,

rarely falling below 2000 ft., and having a mean elevation of about 3500

ft. (4) The north and west African plains, bordered and traversed by bands

of higher ground, but generally below 2000 ft. This division includes the

great desert of the Sahara.

The third and fourth divisions may be again subdivided. Thus the high

plateaus include:—(a) The South African plateau as far as about 12 deg. S.,

bounded east, west and south by bands of high ground which fall steeply to

the coasts. On this account South Africa has a general resemblance to an

inverted saucer. Due south the plateau rim is formed by three parallel

steps with level ground between them. The largest of these level areas, the

Great Karroo, is a dry, barren region, and a large tract of the plateau

proper is of a still more arid character and is known as the Kalahari

Desert. The South African plateau is connected towards the north-east with

(b) the East African plateau, with probably a slightly greater average

elevation, and marked by some distinct features. It is formed by a widening

out of the eastern axis of high ground, which becomes subdivided into a

number of zones running north and south and consisting in turn of ranges,

tablelands and depressions. The most striking feature is the existence of

two great lines of depression, due largely to the subsidence of whole

segments of the earth's crust, the lowest parts of which are occupied by

vast lakes. Towards the south the two lines converge and give place to one

great valley (occupied by Lake Nyasa), the southern part of which is less

distinctly due to rifting and subsidence than the rest of the system.

Farther north the western depression, sometimes known as the Central

African trough or Albertine rift-valley, is occupied for more than half its

length by water, forming the four lakes of Tanganyika, Kivu, Albert Edward

and Albert, the first-named over 400 m. long and the longest freshwater

lake in the world. Associated with these great valleys are a number of

volcanic peaks, the greatest of which occur on a meridional line east of

the eastern trough. The eastern depression, known as the East African

trough or rift-valley, contains much smaller lakes, many of them brackish

and without outlet, the only one comparable to those of the western trough

being Lake Rudolf or Basso Norok. At no great distance east of this rift-

valley are Kilimanjaro—with its two peaks Kibo and Mawenzi, the former

19,321 ft., and the culminating point of the whole continent—and Kenya

(17,007 ft.). Hardly less important is the Ruwenzori range (over 16,600

ft.), which lies east of the western trough. Other volcanic peaks rise from

the floor of the valleys, some of the Kirunga (Mfumbiro) group, north of

Lake Kivu, being still partially active. (c) The third division of the

higher region of Africa is formed by the Abyssinian highlands, a rugged

mass of mountains forming the largest continuous area of its altitude in

the whole continent, little of its surface falling below 5000 ft., while

the summits reach heights of 15,000 to 16,000 ft. This block of country

lies just west of the line of the great East African trough, the northern

continuation of which passes along its eastern escarpment as it runs up to

join the Red Sea. There is, however, in the centre a circular basin

occupied by Lake Tsana.

Both in the east and west of the continent the bordering highlands are

continued as strips of plateau parallel to the coast, the Abyssinian

mountains being continued northwards along the Red Sea coast by a series of

ridges reaching in places a height of 7000 ft. In the west the zone of high

land is broader but somewhat lower. The most mountainous districts lie

inland from the head of the Gulf of Guinea (Adamawa, &c.), where heights of

6000 to 8000 ft. are reached. Exactly at the head of the gulf the great

peak of the Cameroon, on a line of Volcanic action continued by the islands

to the south-west, has a height of 13,370 ft., while Clarence Peak, in

Fernando Po, the first of the line of islands, rises to over 9000. Towards

the extreme west the Futa Jallon highlands form an important diverging

point of rivers, but beyond this, as far as the Atlas chain, the elevated

rim of the continent is almost wanting.

The area between the east and west coast highlands, which north of 17

deg. N. is mainly desert, is divided into separate basins by other bands of

high ground, one of which runs nearly centrally through North Africa in a

line corresponding roughly with the curved axis of the continent as a

whole. The best marked of the basins so formed (the Congo basin) occupies a

circular area bisected by the equator, once probably the site of an inland

sea. The arid region, the Sahara—the largest desert in the world, covering

3,500,000 sq. m.—extends from the Atlantic to the Red Sea. Though generally

of slight elevation it contains mountain ranges with peaks rising to 8000

ft. Bordered N.W. by the Atlas range, to the N.E. a rocky plateau separates

it from the Mediterranean; this plateau gives place at the extreme east to

the delta of the Nile. That river (see below) pierces the desert without

modifying its character. The Atlas range, the north-westerly part of the

continent, between its seaward and landward heights encloses elevated

steppes in places 100 m. broad. From the inner slopes of the plateau

numerous wadis take a direction towards the Sahara. The greater part of

that now desert region is, indeed, furrowed by old water-channels.

The following table gives the approximate altitudes of the chief

mountains and lakes of the continent:—

Mountains. Ft. Lakes. Ft.

Rungwe (Nyasa) . 10,400 Chad . . . . 8502

Drakensberg . . 10,7002 Leopold II . . 1100

Lereko or Sattima . 13,2143 Rudolf . . . 1250

(Aberdare Range) Nyasa . . . 16453

Cameroon . . 13,370 Albert Nyanza . 20282

Elgon . . . 14,1523 Tanganyika . . 26243

Karissimbi . . Ngami . . . . 2950

(Mfumbiro) . 14,6833 Mweru . . . . 3000

Meru . . . 14,9553 Albert Edward . 30043

Taggharat (Atlas) . 15,0002 Bangweulu. . . 3700

Simen Mountains, . 15,1602 Victoria Nyanza. 37203

Abyssinia Abai . . . . 4200

Ruwenzori . . 16,6193 Kivu . . . . 48293

Kenya . . . 17,0073 Tsana . . . . 5690

Kilimanjaro . . 19,3213 Naivasha . . . 61353

The Hydrographic Systems.—-From the outer margin of the African plateaus

a large number of streams run to the sea with comparatively short courses,

while the larger rivers flow for long distances on the interior highlands

before breaking through the outer ranges. The main drainage of the

continent is to the north and west, or towards the basin of the Atlantic

Ocean. The high lake plateau of East Africa contains the head-waters of the

Nile and Congo: the former the longest, the latter the largest river of the

continent. The upper Nile receives its chief supplies from the mountainous

region adjoining the Central African trough in the neighbourhood of the

equator. Thence streams pour east to the Victoria Nyanza, the largest

African lake (covering over 26,000 sq. m.), and west and north to the

Albert Edward and Albert Nyanzas, to the latter of which the effluents of

the other two lakes add their waters. Issuing from it the Nile flows north,

and between 7 deg. and 10 deg. N. traverses a vast marshy level during

which its course is liable to blocking by floating vegetation. After

receiving the Bahr-el-Ghazal from the west and the Sobat, Blue Nile and

Atbara from the Abyssinian highlands (the chief gathering ground of the

flood-water), it crosses the great desert and enters the Mediterranean by a

vast delta. The most remote head-stream of the Congo is the Chambezi, which

flows south-west into the marshy Lake Bangweulu. From this lake issues the

Congo, known in its upper course by various names. Flowing first south, it

afterwards turns north through Lake Mweru and descends to the forest-clad

basin of west equatorial Africa. Traversing this in a majestic northward

curve and receiving vast supplies of water from many great tributaries, it

finally turns south-west and cuts a way to the Atlantic Ocean through the

western highlands. North of the Congo basin and separated from it by a

broad undulation of the surface is the basin of Lake Chad—-a flat-shored,

shallow lake filled principally by the Shad coming from the south-east.

West of this is the basin of the Niger, the third river of Africa, which,

though flowing to the Atlantic, has its principal source in the far west,

and reverses the direction of flow exhibited by the Nile and Congo. An

important branch, however—the Benue—comes from the south-east. These four

river-basins occupy the greater part of the lower plateaus of North and

West Africa, the remainder consisting of arid regions watered only by

intermittent streams which do not reach the sea. Of the remaining rivers of

the Atlantic basin the Orange, in the extreme south, brings the drainage

from the Drakensberg on the opposite side of the continent, while the

Kunene, Kwanza, Ogowe and Sanaga drain the west corst highlands of the

southern limb; the Volta, Komoe, Bandama, Gambia and Senegal the highlands

of the western limb. North of the Senegal for over 1000 m. of coast the

arid region reaches to the Atlantic. Farther north are the streams, with

comparatively short courses, which reach the Atlantic and Mediterranean

from the Atlas mountains.

Of the rivers flowing to the Indian Ocean the only one draining any large

part of the interior plateaus is the Zambezi, whose western branches rise

in the west coast highlands. The main stream has its rise in 11 deg. 21'

3'' S. 24 deg. 22' E. at an elevation of 5000 ft. It flows west and south

for a considerable distance before turning to the east. All the largest

tributaries, including the Shire, the outflow of Lake Nyasa, flow down the

southern slopes of the band of high ground which stretches across the

conbnent in 10 deg. to 12 deg. S. In the south-west the Zambezi system

interlaces with that of the Taukhe (or Tioghe), from which it at times

receives surplus water. The rest of the water of the Taukhe, known in its

middle course as the Okavango, is lost in a system of swamps and saltpans

which formerly centred in Lake Ngami, now dried up. Farther south the

Limpopo drains a portion of the interior plateau but breaks through the

bounding highlands on the side of the continent nearest its source. The

Rovuma, Rufiji, Tana, Juba and Webi Shebeli principally drain the outer

slopes of the East African highlands, the last named losing itself in the

sands in close proximity to the sea. Another large stream, the Hawash,

rising in the Abyssinian mountains, is lost in a saline depression near the

Gulf of Aden. Lastly, between the basins of the Atlantic and Indian Oceans

there is an area of inland drainage along the centre of the East African

plateau, directed chiefly into the lakes in the great rift-valley. The

largest river is the Omo, which, fed by the rains of the Abyssinian

highlands, carries down a large body of water into Lake Rudolf. The rivers

of Africa are generally obstructed either by bars at their mouths or by

cataracts at no great distance up-stream. But when these obstacles have

been overcome the rivers and lakes afford a network of navigable waters of

vast extent.

The calculation of the areas of African drainage systems, made by Dr A.

Bludau (Petermanns Mitteilungen, 43, 1897, pp. 184-186) gives the following

general results:—

Basin of the Atlantic . . . . . 4,070,000 sq. m.

'' '' Mediterranean . . . 1,680,000 ''

'' '' Indian Ocean . . . . 2,086,000 ''

Inland drainage area . . . . . 3,452,000 ''

The areas of individual river-basins are:—

Congo (length over 3000 m.) . . 1,425,000 sq. m.

Nile ( '' fully 4000 m.) . . 1,082,0004 ''

Niger ( '' about 2600 m.) . . 808,0005 ''

Zambezi ( '' '' 2000 m.) . . 513,500 ''

Lake Chad . . . . . . . . . 394,000 ''

Orange (length about 1300 m.) . . 370,505 ''

'' (actual drainage area) . . 172,500 ''

The area of the Congo basin is greater than that of any other river

except the Amazon, while the African inland drainage area is greater than

that of any continent but Asia, in which the corresponding area is

4,000,000 sq. m.

The principal African lakes have been mentioned in the description of the

East African plateau, but some of the phenomena connected with them may be

spoken of more particularly here. As a rule the lakes which occupy portions

of the great rift-valleys have steep sides and are very deep. This is the

case with the two largest of the type, Tanganyika and Nyasa, the latter of

which has depths of 430 fathoms. Others, however, are shallow, and hardly,

reach the steep sides of the valleys in the dry season. Such are Lake

Rukwa, in a subsidiary depression north of Nyasa, and Eiassi and Manyara in

the system of the eastern rift-valley. Lakes of the broad type are of

moderate depth, the deepest sounding in Victoria Nyanza being under 50

fathoms. Apart from the seasonal variations of level, most of the lakes

show periodic fluctuations, while a progressive desiccation of the whole

region is said to be traceable, tending to the ultimate disappearance of

the lakes. Such a drying up has been in progress during long geologic ages,

but doubt exists as to its practical importance at the present time. The

periodic fluctuations in the level of Lake Tanganyika are such that its

outllow is intermittent. Besides the East African lakes the principal are:—-

Lake Chad, in the northern area of inland drainage; Bangweulu and Mweru,

traversed by the head-stream of the Congo; and Leopold II. and Ntomba

(Mantumba), within the great bend of that river. All, exceot possibly

Mweru, are more or less shallow, and Chad appears to by drying up. The

altitudes of the African lakes have already been stated.

Divergent opinions have been beld as to the mode of origin of the East

African lakes, especially Tanganyika, which some geologists have considered

to represent an old arm of the sea, dating from a time when the whole

central Congo basin was under water; others holding that the lake water has

accumulated in a depression caused by subsidence. The former view is based

on the existence in the lake of organisms of a decidedly marine type. They

include a jelly-fish, molluscs, prawns, crabs, &c., and were at first

considered to form an isolated group found in no other of the African

lakes; but this supposition has been proved to be erroneous.

Islands.—With one exception—-Madagascar—the African islands are small.

Madagascar, with an area of 229,820 sq. m., is, after New Guinea and

Borneo, the largest island of the world.

It lies off the S.E. coast of the continent, from which it is separated

by the deep Mozambique channel, 250 m. wide at its narrowest point.

Madagascar in its general structure, as in flora and fauna, forms a

connecting link between Africa and southern Asia. East of Madagascar are

the small islands of Mauritius and Reunion. Sokotra lies E.N.E. of Cape

Guardafui. Off the north-west coast are the Canary and Cape Verde

archipelagoes. which, like some small islands in the Gulf of Guinea, are of

volcanic origin.

Climate and Health.—-Lying almost entirely within the tropics, and

equally to north and south of the equator, Africa does not show excessive

variations of temperature. Great heat is experienced in the lower plains

and desert regions of North Africa, removed by the great width of the

continent from the influence of the ocean, and here, too, the contrast

between day and night, and between summer and winter, is greatest. (The

rarity of the air and the great radiation during the night cause the

temperature in the Sahara to fall occasionally to freezing point.) Farther

south, the heat is to some extent modified by the moisture brought from the

ocean, and by the greater elevation of a large part of the surface,

especially in East Africa, where the range of temperature is wider than in

the Congo basin or on the Guinea coast. In the extreme north and south the

climate is a warm temperate one, the northern countries being on the whole

hotter and drier than those in the southern zone; the south of the

continent being narrower than the north, the influence of the surrounding

ocean is more felt. The most important climatic differences are due to

variations in the amount of rainfall. The wide heated plains of the Sahara,

and in a lesser degree the corresponding zone of the Kalahari in the south,

have an exceedingly scanty rainfall, the winds which blow over them from

the ocean losing part of their moisture as they pass over the outer

highlands, and becoming constantly drier owing to the heating effects of

the burning soil of the interior; while the scarcity of mountain ranges in

the more central parts likewise tends to prevent condensation. In the inter-

tropical zone of summer precipitation, the rainfall is greatest when the

sun is vertical or soon after. It is therefore greatest of all near the

equator, where the sun is twice vertical, and less in the direction of both

tropics. The rainfall zones are, however, somewhat deflected from a due

west-to-east direction, the drier northern conditions extending southwards

along the east coast, and those of the south northwards along the west.

Within the equatorial zone certain areas, especially on the shores of the

Gulf of Guinea and in the upper Nile basin, have an intensified rainfall,

but this rarely approaches that of the rainiest regions of the world. The

rainiest district in all Africa is a strip of coastland west of Mount

Cameroon, where there is a mean annual rainfall of about 390 in. as

compared with a mean of 458 in. at Cherrapunji, in Assam. The two distinct

rainy seasons of the equatorial zone, where the sun is vertical at half-

yearly intervals, become gradually merged into one in the direction of the

tropics, where the sun is overhead but once. Snow falls on all the higher

mountain ranges, and on the highest the climate is thoroughly Alpine. The

countries bordering the Sahara are much exposed to a very dry wind, full of

fine particles of sand, blowing from the desert towards the sea. Known in

Egypt as the khamsin, on the Mediterranean as the sirocco, it is called on

the Guinea coast the harmattan. This wind is not invariably hot; its great

dryness causes so much evaporation that cold is not infrequently the

result. Similar dry winds blow from the Kalahari in the south. On the

eastern coast the monsoons of the Indian Ocean are regularly felt, and on

the south-east hurricanes are occasionally experienced.

While the climate of the north and south, especially the south, is

eminently healthy, and even the intensely heated Sahara is salubrious by

reason of its dryness, the tropical zone as a whole is, for European races,

the most unhealthy portion of the world. This is especially the case in the

lower and moister regions, such as the west coast, where malarial fever is

very prevalent and deadly; the most unfavourable factors being humidity

with absence of climatic variation (daily or seasonal). The higher

plateaus, where not only is the average temperature lower, but such

variations are more extensive, are more healthy; and in certain localities

(e.g. Abyssinia and parts of British East Africa) Europeans find the

climate suitable for permanent residence. On tablelands over 6500 ft. above

the sea, frost is not uncommon at night, even in places directly under the

equator. The acclimatization of white men in tropical Africa generally is

dependent largely on the successful treatment of tropical diseases.

Districts which had been notoriously deadly to Europeans were rendered

comparatively healthy after the discovery, in 1899, of the species of

mosquito which propagates malarial fever, and the measures thereafter taken

for its destruction and the filling up of swamps. The rate of mortality

among the natives from tropical diseases is also high, one of the most

fatal being that known as sleeping sickness. (The ravages of this disease,

which also attacks Europeans, reached alarming proportions between 1893 and

1907, and in the last-named year an international conference was held in

London to consider measures to combat it.) When removed to colder regions

natives of the equatorial districts suffer greatly from chest complaints.

Smallpox also makes great ravages among the negro population.

Flora.—The vegetation of Africa follows very closely the distribution of

heat and moisture. The northern and southern temperate zones have a flora

distinct from that of the continent generally, which is tropical. In the

countries bordering the Mediterranean are groves of oranges and olive

trees, evergreen oaks, cork trees and pines, intermixed with cypresses,

myrtles, arbutus and fragrant tree-heaths. South of the Atlas range the

conditions alter. The zones of minimum rainfall have a very scanty flora,

consisting of plants adapted to resist the great dryness. Characteristic of

the Sahara is the date-palm, which flourishes where other vegetation can

scarcely maintain existence, while in the semidesert regions the acacia

(whence is obtained gum-arabic) is abundant. The more humid regions have a

richer vegetation —dense forest where the rainfall is greatest and

variations of temperature least, conditions found chiefly on the tropical

coasts, and in the west African equatorial basin with its extension towards

the upper Nile; and savanna interspersed with trees on the greater part of

the plateaus, passing as the desert regions are approached into a scrub

vegetation consisting of thorny acacias, &c. Forests also occur on the

humid slopes of mountain ranges up to a certain elevation. In the coast

regions the typical tree is the mangrove, which flourishes wherever the

soil is of a swamp character. The dense forests of West Africa contain, in

addition to a great variety of dicotyledonous trees, two palms, the Elaeis

guincensis (oil-palm) and Raphia vinifera (bamboo-palm), not found,

generally speaking, in the savanna regions. The bombax or silk-cotton tree

attains gigantic proportions in the forests, which are the home of the

indiarubber-producing plants and of many valuable kinds of timber trees,

such as odum (Chlorophora excelsa), ebony, mahogany (Khaya senegalensis),

African teak or oak (Oldfieldia africana) and camwood (Baphia nitida.) The

climbing plants in the tropical forests are exceedingly luxuriant and the

undergrowth or ``bush'' is extremely dense. In the savannas the most

characteristic trees are the monkey bread tree or baobab (Adanisonia

digitata), doom palm (Hyphaene) and euphorbias. The coffee plant grows wild

in such widely separated places as Liberia and southern Abyssinia. The

higher mountains have a special flora showing close agreement over wide

intervals of space, as well as affinities with the mountain flora of the

eastern Mediterranean, the Himalayas and Indo-China (cf. A. Engler, Uber

die Hochgebirgsflora des tropischen Afrika, 1892).

In the swamp regions of north-east Africa the papyrus and associated

plants, including the soft-wooded ambach, flourish in immense quantities—-

and little else is found in the way of vegetation. South Africa is largely

destitute of forest save in the lower valleys and coast regions. Tropical

flora disappears, and in the semi-desert plains the fleshy, leafless,

contorted species of kapsias, mesembryanthemums, aloes and other succulent

plants make their appearance. There are, too, valuable timber trees, such

as the yellow pine (Podocarpus elongatus), stinkwood (Ocotea), sneezewood

or Cape ebony (Pteroxylon utile) and ironwood. Extensive miniature woods of

heaths are found in almost endless variety and covered throughout the

greater part of the year with innumerable blossoms in which red is very

prevalent. Of the grasses of Africa alfa is very abundant in the plateaus

of the Atlas range.

Fauna.—The fauna again shows the effect of the characteristics of the

vegetation. The open savannas are the home of large ungulates, especially

antelopes, the giraffe (peculiar to Africa), zebra, buffalo, wild ass and

four species of rhinoceros; and of carnivores, such as the lion, leopard,

hyaena, &c. The okapi (a genus restricted to Africa) is found only in the

dense forests of the Congo basin. Bears are confined to the Atlas region,

wolves and foxes to North Africa. The elephant (though its range has become

restricted through the attacks of hunters) is found both in the savannas

and forest regions, the latter being otherwise poor in large game, though

the special habitat of the chimpanzee and gorilla. Baboons and mandrills,

with few exceptions, are peculiar to Africa. The single-humped camel—as a

domestic animal—is especially characteristic of the northern deserts and

steppes.

The rivers in the tropical zone abound with hippopotami and crocodiles,

the former entirely confined to Africa. The vast herds of game, formerly so

characteristic of many parts of Africa, have much diminished with the

increase of intercourse with the interior. Game reserves have, however,

been established in South Africa, British Central Africa, British East

Africa, Somahland, &c., while measures for the protection of wild animals

were laid down in an international convention signed in May 1900.

The ornithology of northern Affica presents a close resemblance to that

of southern Europe, scarcely a species being found which does not also

occur in the other countries bordering the Mediterranean. Among the birds

most characteristic of Africa are the ostrich and the secretary-bird. The

ostrich is widely dispersed, but is found chiefly in the desert and steppe

regions. The secretary-bird is common in the south. The weaver birds and

their allies, including the long-tailed whydahs, are abundant, as are,

among game-birds, the francolin and guinea-fowl. Nany of the smaller birds,

such as the sun-birds, bee-eaters, the parrots and halcyons, as well as the

larger plantain-eaters, are noted for the brilliance of their plumage. Of

reptiles the lizard and chameleon are common, and there are a number of

venomous serpents, though these are not so numerous as in other tropical

countries. The scorpion is abundant. Of insects Africa has many thousand

different kinds; of these the locust is the proverbial scourge of the

continent, and the ravages of the termites or white ants are almost

incredible. The spread of malaria by means of mosquitoes has already been

mentioned. The tsetse fly, whose bite is fatal to all domestic animals, is

common in many districts of South and East Africa. Fortunately it is found

nowhere outside Africa. (E. HE.; F. R. C.)

1 With the islands, 11,498,000 sq. m.

2 Estimated.

3 See the calculations of Capt. T. T. Behrens, Geog. Journal, vol. xxix.

(1907).

4 The estimate of Capt. H. G. Lyons in 1905 was 1,107,227 sq. mi.

5 including waterless tracts naturally belonging to the river-basin.

II. GEOLOGY

In shape and general geological structure Africa bears a close

resemblance to India. Both possess a meridional extension with a broad east

and west folded region in the north. In both a successive series of

continental deposits, ranging from the Carboniferous to the Rhaetic, rests

on an older base of crystalline rocks. In the words of Professor Suess,

``India and Africa are true plateau countries.''

Of the primitive axes of Africa few traces remain. Both on the east and

west a broad zone of crystalline rochs extends parallel with the coast-line

to form the margin of the elevated plateau of the interior. Occasionally

the crystalline belt comes to the coast, but it is usually reached by two

steps known as the coastal belt and foot-plateau. On the flanks of the

primitive western axis certain ancient sedimentary strata are thrown into

folds which were completed before the commencement of the mesozoic period.

In the south, the later palaeozoic rocks are also thrown into acute folds

by a movement acting from the south, and which ceased towards the close of

the mesozoic period. In northern Africa the folded region of the Atlas

belongs to the comparatively recent date of the Alpine system. None of

these earth movements affected the interior, for here the continental

mesozoic deposits rest, undisturbed by folding, on the primary sedimentary

and crystalline rocks. The crystalline massif, therefore, presents a solid

block which has remained elevated since early palaeozoic times, and against

which earth waves of several geological periods have broken.

The formations older than the mesozoic are remarkably unfossiliferous, so

that the determination of their age is frequently a matter of speculation,

and in the following table the European equivalents of the pre-Karroo

formations in many regions must be regarded as subject to considerable

revision.

Rocks of Archean age cover wide areas in the interior, in West and East

Africa and across the Sahara. Along the coastal margins they underlie the

newer formations and appear in the deep valleys and kloofs wherever

denudation has laid them bare. The prevailing types are granites, gneisses

and schists. In the central regions the predominant strike of the fohae is

north and south. The rocks, for convenience classed as pre-Cambrian, occur

as several unconformable groups, chiefly developed in the south where alone

their stratigraphy has been determined. They are unfossiliferous, and in

the absence of undoubted Cambrian, Ordovician and Silurian strata in Africa

they may be regarded as of older date than any of these formations. The

general occurrence of jasper-bearing rocks is of interest, as these are

always present in the ancient pressure-altered sedimentary formations of

America and Europe. Some unfossiliferous conglomerates, sandstones and

dolomites in South Africa and on the west coast are considered to belong to

the Cambrian, Ordovician and Silurian formations, but merely from their

occurrence beneath strata yielding Devonian fossils. In Cape Colony the

Silurian age of the Table Mountain Sandstone is based on such evidence.

The Devonian and Carboniferous formations are well represented in the

north and south and in northern Angola.

Up to the close of the palaeozoic period the relative positions of the

ancient land masses and oceans remain unsolved; but the absence of marine

strata of early palaeozoic age from Central Africa points to there being

land in this direction. In late Carboniferous times Africa and India were

undoubtedly united to form a large continent, called by Suess Gondwana

Land. In each country the same succession of the rocks is met with; over

both the same specialized orders of reptiles roamed and were entombed.

The interior of the African portion of Gondwana Land was occupied by

several large lakes in which an immense thickness—amounting to over 18,000

ft. in South Africa—-of sandstones and marls, forming the Karroo system,

was laid down. This is par excellence the African formation, and covers

immense areas in South Africa and the Congo basin, with detached portions

in East Africa. During the whole of the time—-Carboniferous to Rhaetic—that

this great accumulation of freshwater beds was taking place, the interior

of the continent must have been undergoing depression. The commencement of

the period was marked by one of the most wonderful episodes in the

geological history of Africa. Preserved in the formation known as the Dwyka

Conglomerate, are evidences that at this time the greater portion of South

Africa was undergoing extreme glaciation, while the same conditions appear

to have prevailed in India

TABLE OF FORMATIONS

Sedimentary. Igneous.

Recent Alluvium; travertine;

coral; sand dunes; continental } Some volcanic

islands;

dunes. Generally distributed } rift-valley

volcanoes.

Pleistocene. Ancient alluviums and }

gravels; travertine. }

Generally distributed. } A long-continued

Pliocene. N. Africa; Madagascar. } succession in the

} central and

northern

Miocene. N. Africa. } regions and among

} the island

groups.

Oligocene. N. Africa. } Doubtfully represented

} south of the

Zambezi.

Eocene. N. Africa, along east and }

west coasts; Madagascar. }

Cretaceous Extensively developed in } Diamond pipes of S.

N. Africa; along coast } Africa; Kaptian

and foot-plateaus in east } fissure

eruptions;

and west; Madagascar. } Ashangi traps of

} Abyssinia

{Jurassic N. Africa; E. Africa;

K{ Madagascar; Stormberg } Chief volcanic

period

a{ period (Rhaeric) in S. } in S. Africa

r{ Africa }

r{Trias. Beaufort Series in S. }

o{ Africa; Congo basin; }

o{ Central Africa; Algeria; }

{ Tunis. }

{Permian. Ecca Series in S. Africa. } Feebly, if anywhere

} developed.

Carboniferous. N. Africa; Sabaki Shales }

in E. Africa; Dwyka }

and Wittebery Series in }

South Africa }

Devonian. N. Africa; Angola; Bokkeveld } Not recorded.

Series in S. Africa }

Silurian. {Table Mountain Sandstone }

{ in S. Africa, Silurian(?). }

Ordovician. { Doubtfully represented } Klipriversberg and

{ in N. Africa, French } and Ventersdorp

Series

Cambrian { Congo, Angola. and by } of the Transvaal (?).

{ Vaal River and Waterberg }

{ Series in S. Africa }

Pre-Cambrian. Quartzites, conglomerates }

phyllites, jasper-bearing } S. Africa and

generally.

rocks and schists. }

Generally distributed. }

Archeaan. Gneisses and schists of the } Igneous complex of

continental platform. } sheared igneous

} rocks;granites.

and Australia. At the close of the Karroo period there was a remarkable

manifestation of volcanic activity which again has its parallel in the

Deccan traps of India.

How far the Karroo formation extended beyond its present confines has not

been determined. To the east it reached India. In the south all that can be

said is that it extended to the south of Worcester in Cape Colony. The

Crystal Mountains of Angola may represent its western boundary; while the

absence of mesozoic strata beneath the Cretaceous rocks of the mid-Sahara

indicates that the system of Karroo lakeland had here reached its most

northerly extension. Towards the close of the Karroo period, possibly about

the middle, the southern rim of the great central depression became ridged

up to form the folded regions of the Zwaarteberg, Cedarberg and Langeberg

mountains in Cape Colony. This folded belt gives Africa its abrupt southern

termination, and may be regarded as an embryonic indication of its present

outline. The exact date of the maximum development of this folding is

unknown, but it had done its work and some 10,000 ft. of strata had been

removed before the commencement of the Cretaceous period. It appears to

approximate in time to the similar earth movement and denudation at the

close of the palaeozoic period in Europe. It was doubtless connected with

the disruption of Gondwana Land, since it is known that this great

alteration of geographical outline commenced in Jurassic times.

The breaking up of Gondwana Land is usually considered to have been

caused by a series of blocks of country being let down by faulting with the

consequent formation of the Indian Ocean. Other blocks, termed horsts,

remained unmoved, the island of Madagascar affording a striking example. In

the African portion Ruwenzori is regarded by some geologists to be a block

mountain or horst.

In Jurassic times 1he sea gained access to East Africa north of

Mozambique, but does not appear to have reached far beyond the foot-plateau

except in Abyssinia.

The Cretaceous seas appear to have extended into the central Saharan

regions, for fossils of this age have been discovered in the interior. On

the west coast Cretaceous rocks extend continuously from Mogador to Cape

Blanco. From here they are absent up to the Gabun river, where they

commence to form a narrow fringe as far as the Kunene river, though often

overlain by recent deposits. They are again absent up to the Sunday river

in Cape Colony, where Lower Cretaceous rocks (for long considered to be of

Oolitic age) of an inshore character are met with. Strata of Upper

Cretaceous age occur in Pondoland and Natal, and are of exceptional

interest since the fossils show an intermingling of Pacific types with

other forms having European affinities. In Mozambique and in German East

Africa, Cretaceous rocks extend from the coast to a distance inland of over

100 m.

Except in northern Africa, the Tertiary formations only occur in a few

isolated patches on the east and west coasts. In northern Africa they are

well developed and of much interest. They contain the well-known nummulitic

limestone of Eocene age, which has been traced from Egypt across Asia to

China. The Upper Eocene rocks of Egypt have also yielded primeval types of

the Proboscidea and other mammalia. Evidences for the greater extension of

the Eocene seas than was formerly considered to be the case have been

discovered around Sokoto. During Miocene times Passarge considers that the

region of the Zambezi underwent extreme desiccation.

The effect of the Glacial epoch in Europe is shown in northern Africa by

the moraines of the higher Atlas, and the wider extension of the glaciers

on Kilimanjaro, Kenya and Ruwenzori, and by the extensive accumulations of

gravel over the Sahara.

The earliest signs of igneous activity in Africa are to be found in the

granites, intrusive into the older rocks of the Cape peninsula, into those

of the Transvaal, and into the gneisses and schists of Central Africa. The

Ventersdorp boulder beds of the Transvaal may be of early palaeozoic age;

but as a whole the palaeozoic period in Africa was remarkably free from

volcanic and igneous disturbances. The close of the Stormberg period

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