48 NORTH-EAST AFRICA. 



lake, which rises slowly during the floods, and falls imperceptibly during the dry 

 season. The yearly discrepancy between the levels of the lake scarcely exceeds 

 forty inches. 



The Abai, its largest affluent, rises at Gish Abai, near the north-east foot of 

 Mount Denguiya, some 60 miles from the lake. The Portuguese colony settled in 

 this region towards the end of the sixteenth century certainly visited the sources 

 of the Abai ; but they were first described by the Jesuit Paez, who tells us that 

 the water, oozing from a marshy field, is collected in a limpid lake, supposed by the 

 natives to be " unfathomable " because they cannot reach the bottom with their 

 spears. Thence trickles a rivulet, whose course can be traced only by a surface 

 growth of waving grasses, but which over a mile lower down emerges in the open. 

 This is the brook to which both the Portuguese and Bruce gave the name of the 

 Nile. The fiery exhalations often seen flitting about its source, doubtless will-o'- 

 the-wisps, have earned for the Abai the veneration of the natives, who still 

 sacrifice animals to the local river genius. The stream has a width of over 30 feet 

 where it reaches the south-west inlet of the lake, and where its turbid waters have 

 developed an alluvial delta of considerable size. But the outlet, which retains the 

 name of Abai, is a limpid blue current fully entitled to its Arabic designation of 

 Bahr-el-Azraq. Like most other rivers which are at once affluents and emissaries of 

 lacustrine basins, the Abai is constantly said to traverse lake Tsana without mingling 

 with its water. But although such a phenomenon is well-nigh impossible, a 

 perceptible current certainly appears to set steadily from the mouth of the affluent 

 to that of the outflow. 



Tsana cannot be compared for size to the great equatorial lakes. According to 

 Stecker's survey, it has a superficial area of scarcely 1,200 square miles, or less than 

 the twentieth part of Victoria Nyanza. But it must have formerly been more 

 extensive than at present, as is evident from some alluvial plains found especially 

 on the north side. It has the general form of a crater, except towards the south, 

 where it develops into a gulf in the direction of its outlet. Hence the hypothesis 

 advanced by several authors that it may have originally been a vast volcanic cone, 

 and certainly some of the rounded islets in the neighbouring waters look like 

 extinct craters, while the surrounding shores are diversified with bold basaltic 

 headlands. The central part of the basin is probably very deep, for even in the 

 southern inlet Stecker recorded a depth of 240 feet. The water is extremely pure, 

 and as pleasant to the taste as that of the Nile. Towards the south-west the shore 

 is fringed with dense masses of a long light reed {arundo douax), with which the 

 natives construct their tankuas, frail skiffs or rafts propelled by two or four oars, 

 and provided with raised benches to keep the cargo dry. But very little traffic is 

 carried on from coast to coast. Through the foliage which encircles this lovely 

 sheet of water, little is visible except the distant hills and the conic islets rising 

 above the sparkling surface. Herds of hippopotami are often seen on the shores, 

 but there are no crocodiles in the lake, although the Abai below the cataract is 

 infested by these reptiles. Nor has any European traveller seen the aila, a small 

 species of manatee said by the natives to inhabit its waters ; which, however, abound 



