Anglo Sudan 39 -Egyptian] FRONTIER HISTORY а .

Nile, the Sobat, and their tributaries, is of vital impor tance, as the amount exceeds that supplied from any other source . The same treaty therefore forbade the construction of any work across the Blue Nile, the Sobat, or Lake Tsana which might arrest the flow of their waters into the Nile, except by agreement with the Governments of Great Britain and the Sudan . This clause has been duly observed , and no such work attempted. The idea of a regulating barrage at the lake led to the despatch in 1915 of a joint mission of enquiry by agreement with the Abyssinian Govern ment; but circumstances prevented any great result from this mission, which returned to the Sudan early in 1916 .

The actual frontier from the Setit on the north to lat . 6° N. on the south has been ( 1903 and 1909 ) par tially surveyed , but the section from the Sobat to Lake Rudolf is still provisional and not fully explored. Except where it follows the course of a river, it cannot be said to be in any case delimited . Slave-raiding slave-smuggling, arms-smuggling , ivory -poaching, have all contributed since 1899, and especially since the retirement of the Emperor Menelik (1910 ), to keep this frontier in a most disturbed condition . The tribes of the south -eastern Sudan (especially the Nuer, Beir, Berti, and Burun) have suffered constant raids by the Galla, Anuak , and other Abyssinian highlanders.

To check the evil the Sudan has been thrown of late years entirely on its own resources . The Jebel Jerok punitive expedition of 1904 had some Abyssinian help in suppressing the slave-raiders under Ibrahim Wad Mahmud. From 1907 to 1912 raids from over the fron tier, as on Gezan, Jebel Kashangaru , and Jebel Faronge, were of annual occurrence . Vigilance patrols have constantly to intercept the jellabas, or mer chants, who smuggle slaves over the border into the Sudan. Since 1911 the smuggling of armsand am munition has been a still greater evil, affecting Uganda as well as the Sudan. The Anuak are said to have acquired 25,000 rifles in this year, and the Sudanese a