38 [ No. 98 HISTORY border does the political coincide with the ethnical frontier. The large nomad tribe of the Beni Ameron the former, that of the Anuak on the latter , are divided between the Sudan and its neighbour. In both cases this has led to difficulties. On the Eritrean frontier the nomad, of sheer necessity, desires to move his flocks and herds from pasturage to pasturage, according to the various seasons of theyear, andthus tocome down every autumn from the Eritrean hills to the Kassala and Atbara plains . The problem has been further complicated by the constant recurrence of cattle disease in Eritrea . Full liberty of action to permit or prohibit such migration was reserved by both Governments in the Sabderat Agreement of February 28 , 1901 , which superseded earlier arrangements of 1895 and 1898. At present such migrations are discouraged. Both in this matter and in that of the utilisation of the waters of the Gash for storage and irrigation purposes ( one of great importance to Kassala ) the goodwill of the Italian authorities and border officers has never been lacking Relations with Eritrea throughout the period have been most friendly, and , save for spasmodic acts of brigandage, the peace of the frontier has been undisturbed . The chief need is the building of the railway from Thamiam on the Red Sea line to Kassala town ( see p . 83) .

( e ) The Abyssinian Frontier .-A treaty with Ethiopia of May 15 , 1902, defined the frontier between Abyssinia and the Sudan, and gave the latter certain trade facilities and railway concessions. Of the last no use has been made. For trade purposes a block of territory was leased to the Sudan at Itang on the Baro ( see Appendix III) for which in 1904thepresent com mercial station at Gambela was substituted. Hence a road runs to Addis Abbaba, and here , too , is the only wireless station in Abyssinia . More than three quarters of the total Sudan trade with Abyssinia passes through Gambela .

To the Sudan, as to Egypt , the water contributed to the Nile by the rivers rising in Abyssinia, the Blue