Timbuctoo,[195] the great emporium of central Africa, has from time immemorial carried on a very extensive and lucrative trade with the various maritime States of North Africa, viz. Marocco, Tunis, Algier, Tripoli, Egypt, &c. by means of (akkabaahs) accumulated caravans, which cross the great Desert of Sahara, generally between the months of September and April inclusive; these akkabaahs consist of several hundred loaded camels, accompanied by the Arabs who let them to the merchants, for the transport of their merchandize to Fas, Marocco, &c. at a very low rate. During their route, they are often exposed to the attacks of the roving Arabs of Sahara, who generally commit their depredations as they approach the confines of the Desert. [Illustration:_Pl. XIII._ Map _shewing the_ TRACT as followed by the CARAVANS _from_ _FAS to TIMBUCTOO_ by _Jas. G. Jackson,_ 1811. _London Published Augst. 30th. 1811. by G. & W. Nicoll Pall Mall._] In this fatiguing journey, the akkabaahs do not proceed in a direct line across the trackless Desert to the place of their destination, but turn occasionally eastward or westward, according to the situation of certain fertile, inhabited, and cultivated spots, interspersed in various parts of Sahara, like islands in the ocean, called Oas,[196] or Oases; these serve as watering-places to the men, as well as to feed, refresh, and replenish the hardy and patient camel: at each of these Oases, the akkabaah sojourns about seven days, and then proceeds on its journey, until it reaches another spot of the same description. In the intermediate journies, the hot and impetuous winds denominated Shume,[197] convert the Desert into a moveable sea, aptly denominated by the Arabs (El Bahar billa maa), a sea without water, more dangerous than the perfidious waves of the ocean. In the midst of the latter the pilot always entertains some hopes, but in these parching Deserts, the traveller never expects safety, but from the cessation of the wind. If it continues, the most numerous caravans are often buried under mountains of sand, which, like the tempestuous billows in a storm, advance in an undulating manner, stopping and accumulating wherever they find the smallest substance to impede their progress, insomuch that in a few hours a mountain of sand is thus accumulated, where it was before an uninterrupted plain, then the wind shifting, scatters in the air these newly constructed mountains, forming amidst this chaos dreadful gulphs and yawning abysses; the traveller continually deceived by the aspect of the place, can discover his situation only by the position of the stars; moreover the desiccating nature of these winds is such, that they exhale the water carried in skins by the camels for the use of the passengers and drivers; on these occasions, the Arabs and people of Soudan affirm, that 500 dollars have been given for a draught of water, and that 10 or 20 are commonly given when a partial exhalation has occurred.