Page:Africa by Élisée Reclus, Volume 4.djvu/357

 LAKE NYASSA. 285 of the Zambose delta. The Ligonya, which reaches the coast midway between Quelimane and Mozambique, as well as the Lurio (Lu-Rio), which waters the Lomwe territory, discharging into a bay about 120 miles north of the capital, have also their farthest headstreams in the Namuli uplands. Numerous other less copious watercourses rising in the advanced spurs of the same hilly districts have their estuaries on the seaboard between the Lurio and Rovuma mouths. The Rovuma (Ro-Vuma, Ru-Vuma), which forms the northern frontier line of Mozambique, is a considerable stream whose basin comprises nearly the whole eastern drainage of the mountains skirting the east side of Nyassa. Its farthest affluents even rise to the south of the lake, their united waters forming the Lienda or Lujenda (Lu-Jenda), which for the length of its course must be regarded as the main upper branch of the Rovuma. Till recently it was even supposed to have its origin some 60 miles farther south in the Milangi hills, and that it consequently traversed Lake Kilwa, the Shirwa of English writers, discovered by Livingstone in 1859. But this lake is now known to be an independent reservoir without any present outflow, although it apparently belongs geologically to the same depres- sion as the Lujenda Valley, with which at some former period it was probably connected. Lake Kilwa. The sill confining the lacustrine basin on the north varies in height from about 14 to 30 feet at the utmost. This low ridge also lies considerably more than a mile from the northern extremity of the lake, and is clothed from one end to the other with large timber, showing that this tract has ceased to be flooded for a period of at least a hundred years. Nevertheless it is quite possible that in exceptionally wet seasons the level of Lake Kilwa may rise suflBciently to fill the sluggish marshy channels at its north-west extremity, and thus effect a communication northwards with the sources of the Lujenda, by skirting the western extremity of the old margin of the lake, where the ground is almost perfectly level. According to the statements of the oldest inhabitants, such communication in point of fact frequently took place before the present century ; but the level of Lake Kilwa has never ceased to fall lower and lower ever since that time. Hence this basin has now no outflow, the inflow being balanced by evaporation, while its waters, formerly fresh and potable, have now become quite saline. In its present condition the lake has an almost perfectly rectangular form, being about 36 miles long, with a mean breadth of 18 miles and a superficial area approximately estimated at 720 square miles. But it is very shallow, especially on the cast side, which is fordable for a long distance from the shore. The deepest part of the basin lies on the west side, under the escarpments of Mount Chikala, which rises precipitously to a height of from 2,000 to 2,600 feet above the lacus- trine level, which itself stands nearly 2,0Q0 feet above the sea. The two rocky islands of Kisi and Kitongwe serve to indicate the direction of a sub-lacustrine ridge which traverses the basin from north-east to south-west. This ridge will