bia there is only sand; but opposite the town there are islands of red decomposed granite. At Goree the rock is a fine basalt, which takes a regular prismatic form, similar to the Giants' Causeway.* Vast tracts of flat country, partly rich and cultivated, partly desert and sandy, extend to the eastern limit, including Soudan, of which the great kingdoms are Houssa and Bornou. In the flat and desert regions, salt lakes and natron lakes, and salt and natron springs, are met with. Beds of rock-salt occur in different places, as at Teleg, north of Timbuctoo, half a day's journey from Taudeny. From this place is exported all the salt from Timbuctoo to Jenne, and from that town to Soudan. The salt is there disposed in beds several feet thick: it is mined into large slabs, which are afterwards sawn into blocks for the market. These mines form the riches of the country. African Gold. This continent, as is well known, affords a considerable quantity of gold, which is found in the form of rolled pieces, or in minute grains, named gold dust, in the alluvium of rivers, lakes, valleys, and the wide-spreading sand of the vast Desert. The northern parts of Africa afford but little gold; while, in the countries to the south of the Great Desert, there are tracts remarkable for the quantity of gold they contain. Thus the flat country, which extends from the foot of the mountains in which are situated the sources of the Gambia, Senegal, and Niger, has, from an early period, afforded gold. Bambouk, which is situated to the north-west of these mountains, furnishes the greatest part of * Geol. Tr., vol. i., New Series, p. 418. the gold which is sold on the western coast of Africa, as well as that which is brought to Morocco, Fez, Algiers, Cairo, and Alexandria. The gold, as is often the case, is accompanied with grains of iron ore, probably the magnetic or black iron ore. Gold mines occur to the south of Timbuctoo. The people employed in these mines are Bambarra negroes, who become wealthy, as all the particles of gold under a certain weight (12 mizams) belong to them. Pieces of gold, weighing several ounces, are sometimes found there. The country of Kordofan, to the south-east of the Great Desert, affords a considerable quantity of gold. The precious metal found in that country is brought to market by the negroes, in quills of the ostrich and vulture. This territory, it would appear, was known to the ancients, who regarded Ethiopia as a country rich in gold. Sulphur is said to occur in Darfur. 4. Great Table-Land of Africa. Of the tableland itself we know very little,—the geological details we are now to lay before our readers being principally illustrative of the mountain-ranges and acclivities that surround this elevated plateau. Geology of the Coast from Sierra Leone to Cape Negro. We shall trace the geological phenomena from Sierra Leone to Cape Negro. The hills around Sierra Leone are of granite, or rather of a porphyritic granitic syenite, in which tourmaline crystals occur. We know nothing whatever of the geology of the Grain Coast and Ivory Coast of Guinea. The Gold Coast is so named from the great trade in gold dust carried on there, which has given rise to many European settlements. We are told that in the * * Geol. Tr., vol. i., New Series, p. 418. interior there are mountains of granite, gneiss, and quartz, and that the gold is collected from the alluvial sands and clays formed from these rocks. Nothing particular is known of the rocks or soils of the Slave Coast. Our young friend and pupil, Thomas Park, son of the celebrated but unfortunate Mungo Park, possessing the enthusiasm and courage of his father, determined on traversing Africa, with the view of ascertaining the history of his father's fate, at that time in some degree unknown, and also of enlarging our knowledge of its natural history and geography. He was landed by order of government at Accra, on the west coast, in 5° N. The last letter we received from this promising young traveller, -for shortly after the commencement of his journey he perished,-was as follows:-" Accra, 17th September, 1827.-I intend to set off to-morrow morning. I have been, as you know, three months here, during which time I have been principally busy with the study of the Ashantee language. Some time ago I made an excursion of about fifty miles into the interior, by way of experiment, and did not fail to look around me and notice the rocks and other natural productions. I have only time to say, that the valley of Accra is about 12 miles in breadth, and 50 miles in length; the bottom is covered with a soft sandstone, and this sandstone, in one place, was observed resting upon clay-slate. The mountains forming the sides of this long valley, as far as I could observe, appear composed of quartz rock and clay-slate, alternating with each other, and disposed in strata ranging S.S.W. and N.N.E., the dip from 30° to 80° (the direction of the dip not mentioned). The quartz rock contains grains of gold, as I ascertained by careful examination. In some blocks of rock (syenite) I noticed a good many crystals of sphene, and in one place saw what I considered to be black manganese ore. It is very hard and heavy, and is fashioned by the Ashantees into balls. The cover of alluvium, in the bottom of the valley and extending down to the seacoast, is of such a nature as to lead me to conjecture that it is of marine origin, and, therefore, that the sea formerly extended a long way inland. The bases of the hills are richly clothed with trees; but these diminish in number towards the coast, where there occurs only a bush here and there." The occurrence of gold in the quartz rock, as ascertained by Mr Park, is a very interesting observation, as it allows us to infer that probably much of the gold collected in Africa may have been derived originally from this kind of rock, which, in its broken down and disintegrated state, may have formed the sands and gravels in which gold dust is generally found. In Benin there are mountains (those of Cameroon on the seacoast) said to be 13,000 feet high. The Congo district, through which the Zaire flows, was examined for some distance up the river. The rocks met with were granite, syenite, primitive greenstone, gneiss, mica-slate, clay-slate, and primitive limestone or marble. The kingdom of Angola contains salt pits, from which are extracted large slabs of solid rock-salt. According to Battel, beds of rock-salt, three feet thick, extend over a considerable part of the province of Dembea. The mines of Loanga and Benguela furnish good iron. Copper and silver ores are said also to occur in Angola, particularly in the kingdom of Majomba. There are also some considerable mines of copper in Anziko. Bamba, situated on the coast, has large salt pits. Its mountains, rich in metals, extend as far as Angola. The province of Sandi contains ores of iron and of yellow copper ore. The coast from Cape Negro, in lat. 16° S., to the mouth of the Orange River, an extent upwards of one thousand miles, consists of sand hills, without a tree or drop of water, having in this great space only three bays, which are completely exposed to the north-west wind, viz. the Great Fish Bay, Walvisch Bay, and Angra Pequina. The geology of this coast is entirely unknown. Cape of Good Hope District.-This district is bounded on the north and east by the Orange and Fish Rivers; on the west and south by the ocean. The country extends from S. lat. 26° to S. lat. 33° 55′ 40′′, that of the Cape of Good Hope. It includes the country inhabited by the Hottentot race and the Boshuanas. Distribution of the Chains of Mountains, Plains, and Valleys or Kloofs.-Two great chains of mountains run parallel with the western coast, having between them and the coast a sandy plain from five to ten miles in breadth. From the most easterly of these two chains branch off three others, running in a direction parallel with the equator, between which are the like number of terraces, including altogether a space of between two and three degrees of latitude. The two southernmost of these chains are united at several points with the western, and form the vast ridges which, under the names Zwartebergen or Black Mountains, run |
