“The ambatch is distinguished for the unexampled lightness of its wood, if the fungus-like substance of the stem deserves such a name at all. It shoots up to fifteen or twenty feet in height, and at its base generally attains a thickness of about six inches. The weight of this fungus-wood is so insignificant that it really suggests comparison to a feather. Only by taking it into his hands could anyone believe that it were possible for one man to lift on his shoulders a raft made large enough to carry eight people on the water. The plant shoots up with great rapidity by the quiet places on the shore, and since it roots merely in the water, whole bushes are easily broken off by the force of the wind or stream, and settle themselves afresh in other places. This is the true origin of the grass-barriers so frequently mentioned as blocking up the waters of the Upper Nile, and in many places making navigation utterly impracticable. Other plants have a share in the formation of these floating islands, which daily emerge like the Delos of tradition; among them, in particular, the _Vossia_ grass and the famous papyrus of antiquity, which at present is nowhere to be found on the Nile either in Egypt or in Nubia.” Schweinfurth notices a remarkable extinct volcano called Defafang, one thousand feet high, which is situated some five miles from the east bank of the Nile, in about latitude 10° 50′ north. This extinct volcano was first discovered by Ferdinand Werne, who collected specimens of the rocks,--chiefly basaltic lava. Defafang for a long time was the boundary on that side of the Nile between the territory of the Negroes on the south and that of the more or less Arab shepherds on the north. [Illustration: SHILUKS.] At the village of Kaka, on the east bank of the White Nile, Schweinfurth observed ruins of a fort which had once been the headquarters of a renowned robber chief, Muhammad Kher. This man, who flourished between 1840 and 1855, was a Nubian, who gathered round him a number of well-armed Baggara Arab horsemen. He was one of the first of the slave-traders to show how, by means of fortified stations, it was possible to intimidate the Negroes of the Sudan and bring them into subjection. Muhammed Kher and his Arabs devastated the country for hundreds of miles along the banks of the Nile, exterminating the population in many places. At Kaka Schweinfurth found himself greeted by a great crowd of naked Shiluks, who, prompted by curiosity, assembled on the shore.