Belgian Congo 33 CONVENTIONS WITH FRANCE Notwithstanding the express limitation of the northern frontier of the Free State to the 4th parallel, the officials of the State continued to press north wards. In 1891–2 the Sultanate of Bangasso, lying beyond the Ubanghi river, was occupied, while two years later the French frontier had been pushed back by the encroachments of the Free State frontier officials to the 9th parallel .

(8 ) KING LEOPOLD AND THE NILE Before, however, considering the arrangement which finally settled the Franco-Congolese boundary, it is necessary to refer to the relations of the Free State with Great Britain in the valley of the Upper Nile . Although the surrender of the Egyptian troops under Slatin Pasha and Lupton and the conquest by the Mahdi of the Equatorial Provinces had been followed in 1885 by the withdrawal of the Egyptian frontier to Wadi Halfa, the Anglo -German 1890 Convention had recognized in effect that the Sudan was still an Egyptian appanage. King Leopold , however, not choosing to conform to this view of Great Britain's claims to the district, endeavoured to obtain control of the rich pro vince of Bahr el-Ghazal and to secure an outlet to the Nile. To this end Captain van Kerckhoven, in command of a considerable force, was dispatched to the Upper Welle, whence he made his way to the Nile and there opened up communications with the remains of the old Egyptian garrison at Wadelai . Another Belgian, Hanolet, entered the Shari valley and began to nego tiate with Rabah, the bitter enemy of France, who had carved out a sultanate for himself to the south-east of Lake Chad . Finally the northern posts of Katuaka and Lifi were occupied , and , though the abandonment of these and the Nile posts had to be effected in the face of the Mahdi's advance, the latter's troops were successfully routed in a subsequent engagement on D