Above its mouth we must be prepared to meet the greatest of all the obstructions of the Nile. Here are many small affluents from both east and west, and here is a vast stretch of marsh through which the waters soak as through a sponge. In the centre of this “sponge” tract is a small lake——Lake No. But to reach it or emerge from it again, by means of the labyrinthine channels, is a work of great difficulty. The “sponge” is a thick coating of roots, grasses and stems matted together so as to conceal the waters, yet open enough for them to percolate through. It may be ventured upon by human feet, and in many places supports quite a vegetation. But the traveller is in constant danger of falling through, to say nothing of the danger from various animals. It was through this “sponge” that Colonel Baker, in his second Nile expedition, managed to cut a canal, through which was dragged the first steamer that ever floated on the head waters of the great river. [Illustration: CROSSING A SPONGE.] Having passed this obstacle the journey is easier to Gondokoro, where the land is firm. Twenty-three years ago Gondokoro was a collection of grass huts in the midst of an untrodden wilderness, and surrounded by barbarous and hostile tribes. It has since been made an Egyptian military station and named Ismailia. Though the spot is not inviting except as it affords you rest after your hardships, yet it is the scene of an interesting episode in the history of African exploration. Speke and Grant had started on their memorable trip from Zanzibar in 1861. Colonel Baker and his wife had started up the Nile for its sources in the same year. Now it is February, 1863. A travel stained caravan, with two white men at its head, comes down the high ground back of the station. They quicken their pace and enter the village with shouts, waving of flags and firing of musketry. It is Speke and Grant on their return trip, with the secret of the Nile in their keeping. On their long tramp they had visited strange peoples and countries, and by courage and tact had escaped unharmed from a number of difficulties and perils. They had traced the one shore of that vast reservoir of fresh water under the Equator which Speke had sighted on a previous expedition, and had named Victoria Nyanza. They had seen this beautiful equatorial reservoir discharging its surplus waters northward over the picturesque Ripon Falls, and knew that they were in possession of the secret which all the world had sought from the beginning. Lower down, at the Karuma Falls, they were compelled to leave the stream, which they now felt sure was the Nile. Crossing to the right bank, they struck across the country, northward, and in a direct line for Gondokoro. Here they caught sight of the furthest outpost of Egyptian exploration, and again gladly looked on the river that was to bear them down to the Mediterranean.