Page:Africa by Élisée Reclus, Volume 4.djvu/528

 482 SOUTH AND EAST AFRICA. On the west slope facing the Mozambique Channel some of the rivers, which have their sources on the eastern highlands near the Indian Ocean, develop fluvial basins of considerable extent. South of the Betsileo territory the Mangoka, or St. Vincent, drains a superficial area of not less than 20,000 square miles. Farther north the Tsijobonina is fed by the numerous streams descending from the Ankaratra volcanoes and from all the surrounding igneous districts. To this fluvial system also belongs the lacustrine depression of Lake Itasy, which finds an escu|)c in this direction for its penl-u]) waters. The Ikopa, largest of all the rivers of Madagascar, sends to the Bay of Bom- betok all the drainage of the province of Imeriua, in which is situated the capital of the Ifova kingdom. With its great tributary, the Betsiboka, it has a total length of not less than 500 miles, and according to Sibree, a steamer of light draught might ascend the Betsiboka branch for a distance of 90 miles from the sea. In the north-west part of the island all the more important streams discharge tluir waters into winding and ramifying marine inlets, which pre- sent a remote resemblance to the Scandinavian fjords, but which might be more correctly comimrcd with the indentations on the coast of Brittany. They Hvv ])robably due to an analogous cause, that is to say, the gradual disinte- gruti«)n of the granitic and other rocks along the lines of fracture or least resistance. Numerous islets, surviving fragments of the mainland, obstruct the entrance of the inlets, or continue the headlands seawards. One of these islands is Nossi-Be, evidently a geographical dependence of Madagascar, and famous for its groups of volcanic cones, some of whose extinct craters are now flooded by little lakes. Ac- cording to Grautlidier, the east coast, continually eroded by the marine currents, is gradually receding, except at the points where, as at Tamatave and Foulepointe (Marofototra), the beach is protected by banks of coral reefs. But the opposite process seems to bj at work on the west side of the island, where the land, through the action of the polyps, appears to be steadily gaining on the marine waters. Thus several bays have already bcvn enclosed by the encroachments of the shore-line and transformed to lakes. Climate.. Madagascar, which according to latitude belongs to the torrid zone, enjoys a temperate climate, thanks to the great mean elevation of the land. From the sea- board to the uplands of the interior, observers have recorded a normal decrease of temperature, while the summits of Ankaratra and of the other highlands, penetrate into the frigid zone, the surface of the lakes and tarns being here frequently icebound. But thanks to the surrounding marine waters, whose normal tem- perature is maintained by the warm currents, Madagascar enjoys on the whole a very equable climate, presenting no sudden transitions from heat to cold. At Tananarive, on the elevated inland plateaux, the glass never falls in winter below