Page:Africa by Élisée Reclus, Volume 4.djvu/318

260 SOUTH AND EAST AFRICA. On the west side of Nyassa there occur no ranges comparable to the Living- stone chain, and here the ground rises in some places but little above the mean level of the phitcau itself. Nevertheless, certain isolated masses present a very imposing effect. Such is Mount Chombe, to which the English missionaries have given the name of Waller, and which commands one of the narrowest parts of the lake, near Florence Bay. Chombe forms a pyramidal sandstone mass with alter- nating grey and blackish layers, and rising to a height of 5,500 feet. Other less elevated peaks follow in a southerly direction along the coast between the lake and the plateau, as far as the Molomo Mountains, which project between the Zambose and the lower Shire. Carboniferous deposits of easy access have been discovered in the valleys of the Mount Waller district. Being thus pent up round about most of its periphery by elevated land, Nyassa is fed by no large affluents. At its northern extremity, along the axis of the lacustrine depression, where the explorer Young reported the probable exis- tence of a large emissary, nothing occurs except a few rivulets flowing from the mountains forming the waterparting between Nyassa and Tanganyika. The most copious streams come from the western slope, that is, from the side where the general relief of the land is lowest. On the east or opposite side the parting- line between the waters flowing to Nyassa and the Indian Ocean, runs at but a few miles from the margin of the lake, which consequently from this direction receives only some small affluents, often falling through a series of cascades down to the shore. Altogether Nyassa possesses an extremely limited area of drainage compared with its great superficial area. Hence the water is maintained through- out the year nearly at the same level, the rise and fall scarcely exceeding three feet. According to the report of the missionaries there was a continuous slight subsi- dence during the period from 1875 to 1880. At its southern extremity Nyassa terminates, like Tanganyika, in a " horseshoe," but even more sharply outlined, and this horseshoe is disposed in two secondary bays or inlets, tapering gradually southwards. The Shire and Lower Zambese. From the eastern and longer of these bays, the lacustrine overflow escapes through the outlet of the Shire Eiver. The current is at first broad and sluggish, and soon expands into the little Lake Pamalombe, whose flat banks are every- where overgrown with tall reeds. Beyond this point the Shire continues its southerly course down to the edge of the terrace formation, whence it tumbles over a scries of cataracts in the direction of the Zambese. At these cataracts, which have received the name of the Murchison Falls, all navigation, whether for boats or steamers, is completely arrested, but is resumed lower down and continued with little further obstruction as far as the sandbars blocking the mouths of the Zambese. Throughout the whole of this stretch the only impediment to the traflic are the accumulated masses of tangled aquatic vegetation — nympheacecB and other plants, such as the piitia stratioics and alfasinha, or " lettuce " of the Portu-