They value at, a _piece of India_, a Negro from 15 to 25 years old, who is vigorous, well formed, and has no defect. Three Negro boys or girls, well made and about 10 or 12 years old, are worth two pieces of India; and two children, between 5 and 10, are given and received for one piece. A pound of ivory generally sells on the spot for 1 livre 16 sous; and a drachm of gold, for 10 livres: these articles are paid for in merchandize, according to the value of the bars. Ostrich feathers have no determinate price, but are sometimes given as presents, and at others sold to a good account. When speaking of the Moors, I shall give a description of the gum trade, which they exclusively carry on. * * * * * CHAP. XIII. * * * * * COURSE OF THE SENEGAL, AND DISTINCTION BETWEEN IT AND THE NIGER. — ACCOUNT OF THE PEOPLE WHO OCCUPY ITS BANKS. — KINGDOMS AND INHABITANTS ON THE LEFT SIDE. — ACCOUNT OF KING BRACK, AND HIS LUDICROUS CONDUCT AT AN INTERVIEW WITH THE GOVERNOR. — DEFEAT OF A MOORISH PRINCE. — BATTLE BETWEEN THE VICTOR AND THE KING OF CAYOR, WITH ITS RESULTS. — ANIMALS OF THE BANKS OF THE SENEGAL. THE Senegal, on the banks of which almost all the commerce of western Africa is carried on, and which has given its name to the French establishment in this part of the world, runs from its source for forty leagues or thereabout N. N. W. and then turns due N. as far as the cataracts of Govina: thence it runs to the N. W. till it reaches the cataracts of Felou; W. as far as Galam; N. W. to Faribé; and W. to Serimpalé. From this part it turns abruptly to the S.; and after several curvations it continues the same direction to the sea. In its course it divides itself into several branches, and forms two large lakes and some isles, of which I shall have occasion to speak. It has long been thought that the Senegal and the Niger were the same river; and they were indifferently called by each name. Several ancient and modern authors have maintained this opinion; and others have controverted it. But the discoveries of Mungo Park have irrevocably decided the point; as this traveller has found, that the Senegal and the Niger are two different rivers whose course is opposite; the former running in a western, and the latter in an eastern direction. In all seasons, the Senegal is navigable for small vessels and large boats, from its mouth as far as Podor, and even to Domus, which is twelve leagues higher. It cannot be ascended higher so as to reach Galam, except in the rainy season, when there is sufficient water to navigate vessels from 130 to 150 tons burthen.