Mysterious that sombre forest the gathering shades encompass. Mysterious that tall half-naked figure on yonder ledge, crimson framed in the dying sun, motionless and statuesque. Mysterious that piercing melancholy note which thrills from the profundities beyond, fading away in whispers upon the violet and green wavelets lapping against the side of the boat. Mysterious those rapid staccato drumbeats as unknown humanity on one shore signals to unseen humanity on the other. Mysterious the raucous cry of the crown-birds passing in long lines to their resting-place in the marshes. Mysterious those tiny lights from some unsuspected haunt of natural man that spring into life as the sun sinks to slumber, and darkness, deep unfathomable darkness, rushes over the land there to rest until a blood-red moon, defining once again the line of forest, mounts the sky. [Illustration: OUTLINE MAP OF NORTHERN NIGERIA.] From the point of view of navigation and of commerce the Niger is a most unsatisfactory and uncertain river to work. It can be described, perhaps, as a river full of holes with shallows between them. Its channels are constantly changing. It is full of sandbanks which take on new shapes and sizes every year. The direction of the water-flow below Samabri, where the bifurcation begins, is so unreliable that within a few years the Nun has become virtually useless, the Forcados gaining what the Nun has lost, while there are recent indications that the process may again be altered in favour once more of the Nun to the detriment of the Forcados. In the course of the year the water level varies twenty-seven feet, the period of rise being from June in an ascending scale until the end of September, the fall then commencing, the river being at its lowest from December to May. In the rainy season the banks are flooded in the lower regions for miles around. In the dry season the banks tower up in places fifteen feet above water level. Roughly speaking, the Niger is navigable for steamers drawing five feet in June, six feet in July, and so on up to twelve feet in the end of September; from November to April for vessels drawing between four and five feet. But the conditions of two consecutive years are seldom alike.