great body, otwesien division o f this o c e a n , comprized between Fezzan and the Atlantic, is ho less than 50 caravan journies across, from north to south; or from 750 foi 8ao G . miles ; and double that extent, in length : without doubt ;the largest desert in the world. This division contains but a scanty portion o f islands (or oases) and those also o f small extent; but the eastern division has many; and some o f them very large. Fezzan, G adatti is, Taboo, Ghartat, Agadez, Augela, Berdoa, are amongst, the principal ones : besides which, there are a vast number o f small ones. In éffect, this is the part o f Africa alluded to by Strabo,* when hé says from Ctieius Piso, that Afr ica may be, compared to a leopard’s skin. I coiiCeiVe the reason why the oases are more common here, than in the west, is, that the stratum o f sand is shallower, from its surface, to that o f the earth which it covers; In other words, that the water contained in 1 that earth, is nearer to the surface; as in most o f the oases it springs; up spontaneously.t Can any part: o f the cause be assigned to the prevalent easterly winds, which, by driving the finer particbs o f sand to leeward, may have heaped it up to a higher level in the Sahara, than elsewhere? J T h e springs, no doubt, have produced the oases themselves, by enabling useful vegetables tó flourish, and consequently population to he established. * Page,130. f Water is found at the depth o f a few feet, in Fezzan (Âfr. Assoc, Q^p. 96 : O. p. 14^) ■ - The samé is'said by Pliriy, concerning this quarter of Africa ; lib. v. c .5 . ’Fut farther tó the NW, on thé edge o f the Desert, and in the counfry o f Wadr-eag in partial*- lar (Shaw, p. 135.); wells'are dug to an amazing depth, and water mixed withfipe sand; springs up suddenly, and sometimes fatally to the workmen. The Doctor tells us, that the people call this abyss o f sand and water, “ the sea below ground.” Exactly the same state o f things existe in the country round London, wherè the sánd has in several eases nearly filled up the Wells.- (See Phil. Trans-, for 1797.) The-famous well lately'dug by I t s s l SpENCEk (at-Wimbledon)", of more than 560 feet in depth, has several hundred feet of sand in it. ■< I J Ships that have sailed at a great distancé frotn the AfHbah coast, opposite to C. Blanco and C. Bójador, bavé halt their rigging" filled with finéSand, when the wind blew strong off shore. The accumulation o f the Bissago shoals may have been partly owing tó this cause also. They'Occupy thi- position wherè à great éddy o f the general southerly current takes place, between C. Veid and- Shérbró’ . That the Desert has a dip towards the east, as well as the south, seems to be proved by the course o f the Niger, also. Moreover, the highest points o f North Africa, that is to say, the mountains o f Mandinga and Atlas, are situated very far to the west. The Desert, for the most part, abounds with salt. But we hear o f salt mines only, in the part contiguous to Nigritia, from whence salt is drawn for the use o f those countries, as well as o f the Moorish states adjoining; there being no saltin the Negro countries south o f the Niger.* There are salt lakes also, in the eastern part o f the Desert. Th e great ridge o f mountains, and its branches, are very productive in gold; but more particularly in the quarters opposite to Manding and Bam- bouk on the-west, and Wangara, on the east. It may perhaps admit o f a doubt, whether the gold is brought down at the present time, by the numerous fountains that form the heads o f the Niger and Senegal rivers; or whether it "has been deposited in the lower parts o f their beds, at an earlier period o f the world; and that the search, instead o f being facilitated by the periodical floods, is, on the contrary, only to be pursued with effect, wheti the waters are low. Tombuctoo is reckoned die mart o f the Mandinga gold, from whence it is distributed over the northern quarters o f A frica, by the merchants o f Tunis, Tripoly, Fezzan, and Morocco; all o f whom resort to Tombuctoo. Most o f it, no doubt, afterwards finds its way into Europe. It may be remarked, also, that the Geld Coast o f Guinea (so called, doubtless, from its being the place o f traffic for gold dust), is situated nearly opposite to Manding- but whether the gold brought thither, has been washed Out o f the mountains, b y tbe northern. or southern streams, I know n o t : it may be by both ; for a part o f the gold o f Wangara is brought, for sale, to the southern coast.t * This quality o f the African Desert was fann'fiaity knowiv to; i iriodotna (Melpom, c. 181, et seq.) He knew also that there was salt in'-abundance Tndhe northern parts. But as it would appear that the inhabitants in that quarter can furnish thetnselves With shit of a better quality from the sea, the mines are not wrought. f Some writers have said, that there are gold mines in the neighboürrhoöd o f Mina; on
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