The ‘Nyassi’ is, in fact, a general reservoir into which are thrown the Lakes Tanganyika, the Nyassa, the Shirwa, and the four smaller waters, the Liemba, the Bangweolo, the Moero of the great river Chambeze, and the Liemba drained by the Lufira-Luapula stream. The latter, lying between S. lat. 10°-12°, have lately been reported by Dr Livingstone (Map of the Lake Region of Eastern Africa), showing the Sources of the Nile recently discovered by Dr Livingstone, with notes, &c., by Keith Johnston, jun. (Johnston); and we have a Sketch Map of Dr Livingstone’s recent Explorations—Eine Kartenskizze, &c. From Dr Petermann’s Geographische Mittheilungen, Part V., for May, 1870 (Gotha, Perthes). CHAPTER IV. A STROLL THROUGH ZANZIBAR CITY. ‘E dahi se foi à Ilha de Zanzibar, que he aquèm de Mombaça vinte leguas e tão pegada à terra firma que as náos que passarem per entre ellas, hão de ser vistas.’—DE BARROS, 1, vii. 4. And first of the Port. Zanzibar harbour is a fine specimen of the true Atoll, barrier or fringing reef, built upon a subsiding foundation, probably of sandstone. The original lagoon, charged with sediment and washings from the uplands, must have burst during some greater flood, and split into narrow water-ways the one continuous coralline rim. The same influences may account for the gaps in the straight-lined reef whose breach gave a name to Brazilian Pernambuco. The port varies in depth from 9 to 13 fathoms, with overfalls, and the rise of the tide is 13 feet. Here the Hormos Episalos (statio fluctuosa, or open roadstead of the Periplus, chap. 8) has been converted into a basin by the industry of the lithophyte. These ants of the ocean have built up an arc of ‘Sea-girt isles, That, like to rich and various gems, inlay The unadorned bosom of the deep.’ There is a front harbour and a back bay. The latter enables ships landing cargo to avoid the heavy swell of the N.E. monsoon. The two are separated by Ras Changáni[17]—Sandy Point. The name, corrupted to Shangany, has attached itself in our charts to the whole city. These coral-based islet clumps are readily made in these seas. The rough ridges of a ‘wash,’ where currents meet, are soon heaped with sea-weed, with drift-wood, and with scatters of parasitical testaceæ, which decaying form a thin but fruitful soil. Seeds brought by winds, waves, and birds then germinate; and matter, animal as well as vegetable, is ever added till a humus-bed is formed for thick shrubbery and trees. Unless deposition and vegetation continue to bind the rock, it is liable to be undermined by the sea, when it forms banks dangerous to navigation.