Thus the eastern seaboard presents a double coastline: the outer shore, exposed to the fury of the surf; and the inner beach, washed by the still waters of the muddy winding channel, mostly fringed with mangroves. These estuaries, which receive about fifty small streams from tho interior, and which communicate with the open sea by a few easily accessible passages, present the appearance of a long chain of lakes or lagoons, lining the coast for hundreds of miles. In many places they merge in an inextricuble system of Fig. 133. — Erosions on the east coast and Anton-Gil bay.
tortuous channels, which are sometimes quite dry in summer, and which are known only to a few pilots.
The outer line separating these lagoons from the ocean consists in many places of coral reefs covered by the action of the waves with sands and shells, and thus gradually transformed to a continuous dyke or embankment, which presents an effectual barrier against the encroachments of the sea. Forest trees have here struck root, affording a grateful shade to the numerous villages following continuously along the beach. Under the action of the marine current, which here flows close in-shore, the coastline has acquired a surprisingly regular form. From the inlet of Fort Dauphin, at the south-east corner of the island, for a distance of 540 miles northwards to Marofototra, the seaboard is almost perfectly rectilinear, and vessels frequenting these waters usually keep well off the coast in order to avoid the neighbouring reefs
North of Marofototra the beach no longer presents the same uniformity, and at Anton-Gil Bay even develops a deep inlet under the shelter of a bold volcanic promontory. But the island of St. Mary (Nossi-Boraha), which stretches like a spear-head in front of Tengteng Bay, appears to be the surviving fragment of an outer coastline, which formed a northern continuation of the southern rectilinear wall, and connected Marofototra with Cape Maseala. The ramifying bay of Diego Suarez at the northern extremity of Madagascar owes its existence to the volcanic headland of Amber Cape, which here encloses an extensive body of marine waters.
