One may determine which of the two climates is the more tolerable by considering whether he would prefer to be roasted or stewed. The traveller would find it hard to decide whether the desert or the swamp is the greater bar to his advance. Every mile of progress marks an increase of dampness and of warmth. First of all, we pass through the great mimosa forest, which extends, belt-like, almost across the continent, marking the confines of the Sahara and the Soudan. The reader must not imagine a dense girdle of tall trees and tangled undergrowth, but a park-like country, with wide glades between clumps and lines of thorny shrubbery. The mimosa, or Arabian acacia——the tree from which the gum-arabic of commerce is extracted——has assigned to it the out-post duty in the struggle between tropical luxuriance and desert drought. By and by it gives place to the ambatch as the characteristic tree of the Nile. The margin of the river becomes marshy and reedy. The water encroaches on the land and the land on the water. The muddy stream rolls lazily along between high walls of rank vegetation, and bears whole islands of intertwisted leaves, roots and stems on its bosom, very much as an Arctic strait bears its acres of ice floes. It breaks up into tortuous channels that lead everywhere and nowhere. A nearly vertical sun shines down on the voyager as he slowly toils up stream. Scarcely a breath of air stirs to blow away the malarious mists or fill a drooping sail. Mosquitoes are numerous, and insatiate for blood. Day thus follows day with nothing to break the monotony except now and then the appearance of a hippopotamus, rising snortingly to the surface, a crocodile with his vicious jaws, or, where the land is solid, a buffalo pushing his head through the reeds to take a drink. The true river margin is invisible except from the boat’s masts over the head of the tall papyrus. Even could we reach it, we would wish ourselves back again, for of all the growth of this dismal swamp man is the most repulsive. The Dinka tribes of the White Nile are among the lowest in the scale of human beings. They are naked, both as to clothing and moral qualities. The Shillooks are a finer race physically, but inveterate pirates and murderers. In the midst of this swampy region the Nile receives another important tributary from the mountains of Southern Abyssinia. It is the Sobat which, Speke says, “runs for a seven days’ journey through a forest so dense as to completely exclude the rays of the sun.”