Throughout the Dongola campaign in 1896 the Nile was the main channel of communication between the Expeditionary Force and its base in Egypt. All supplies were brought to the front as far as possible by water transport. Wherever the Nile was navigable, it was used. Other means of conveyance--by railways and pack animals--though essential, were merely supplementary. Boats carry more and cost less than any other form of transport. The service is not so liable to interruption; the plant needs only simple repair; the waterway is ready-made. But the Nile is not always available. Frequent cataracts obstruct its course for many miles. Other long reaches are only navigable when the river is in flood. To join the navigable reaches, and thus preserve the continuity of the communications, a complex system of railways and caravans was necessary. In the expedition to Dongola a line of railway was required to connect the two navigable reaches of the Nile which extend from Assuan to Wady Halfa, and from Kerma to Merawi. Before the capture of Dongola, however, this distance was shortened by the fact that the river at high Nile is navigable between the Third Cataract and Kerma. In consequence it was at first only necessary to construct the stretch of 108 miles between Wady Halfa and Kosheh. During the years when Wady Halfa was the southernmost garrison of the Egyptian forces a strong post had been maintained at Sarras. In the Nile expeditions of 1885 the railway from Halfa had been completed through Sarras and as far as Akasha, a distance of eighty-six miles. After the abandonment of the Soudan the Dervishes destroyed the line as far north as Sarras. The old embankments were still standing, but the sleepers had been burnt and the rails torn up, and in many cases bent or twisted. The position in 1896 may, in fact, be summed up as follows: The section of thirty-three miles from Wady Halfa to Sarras was immediately available and in working order. The section of fifty-three miles from Sarras to Akasha required partial reconstruction. The section of thirty-two miles from Akasha to Kosheh must, with the exception of ten miles of embankment completed in 1885, at once be newly made. And, finally, the section from Kosheh to Kerma must be completed before the Nile flood subsided.