of obelisks, the remains of obstructions not yet entirely removed by the current. Farther on follow other narrows and barriers, especially south of a chain of hills 800 to 1,000 feet high skirting the left bank Here the Niger is joined by the now almost dried-up Wed Tafassasset, which rises on the southern slopes of the Ahaggar hills, and which with its various ramifications probably at one time watered a region as extensive as that of the Joliba itself. The Jallul Bosso valley, in which the whole system converges, is even now never quite waterless, its lower course winding through a district with a yearly rainfall of scarcely less than 20 inches.
Lower down the Niger is joined opposite Gomba by the perennial Gulbi n' Sokoto, or "River of Sokoto," so called from the city of that name situated on its banks. The Sokoto, which rises in the Katsena country, waters the northern zone
of Sudan on the verge of the Saharian savannas; but its bed, from 130 to 250 feet wide, contains very little water except during the floods. Flegel, who surveyed its lower course for 90 miles from Gomba to Birni n' Kebbi, represents it as obstructed by vegetable remains, trunks of trees, and muddy banks.
Below the Sokoto confluence the Niger is still obstructed by some extremely dangerous rapids, Such as those near Bussa, probably the point where Mungo Park perished in 1806. The boatmen who accompanied Flegel in 1880 assured him that at low water the remains of the European boat were still visible, and the brothers Lander obtained from the king of Bussa some books and other documents belonging to the famous explorer. At Geba, where the river is deflected south-eastwards to the Benue confluence, the rocky islet of Kesa rises abruptly 330 feet above the water, and from this point the Niger, still 450 feet
