"Behind this low land comes the old beach of some former age--reefs of white quartz sand, the stunted vegetation of which can only exist because the rainfall is heavy and almost continuous. This is the fringe of the great forest region which extends over the greater part of the country. Here the land rises and becomes hilly, and the rivers are obstructed by a more or less continuous series of rocks, which form rapids and prevent them running dry when the floods recede. Behind these, to the south, the hills gradually rise to mountains of 5,000 feet, and in the case of a peculiar group of sandstone castellated rocks, of which Roraima is the highest, to 8,000 feet. "The numerous rivers bring down vegetable matter in solution, clay and fine sand suspended and great masses of floating trees and grasses. These form islands in the larger estuaries and bars at the mouths of most of the rivers; they also tinge the ocean for about fifty miles beyond the coast from green to a dirty yellow. Wind and wave break down the shore in one place and extend it in another, giving a great deal of trouble to the plantations by tearing away the dams which protect their cultivation. Every large river has its islands, which begin with sand-banks, and by means of the courida and mangrove become ultimately habitable. In the Essequebo there are several of a large extent, on which formerly were many sugar plantations, one of which remains in Wakenaam. The Corentyne and Marowyne have also fair-sized islands, but none of these has ever been settled. Off the coast of Cayenne the rocky Iles du Salut and Connetable are quite exceptional, for the coast is elsewhere a low mud-flat, sloping very gradually, and quite shallow. "The longest river is the Essequebo, which rises in the extreme south, and like most of the larger streams, flows almost due north. It is about 600 miles in length; the Corentyne is nearly as long, and the Marowyne and Oyapok are probably about the same length. Other rivers that would be considered of great importance in Europe are seen at intervals of a few miles all along the coast. The Demerara, on which the capital of British Guiana is situated, is about the size of the Thames, and 250 miles long, and the Surinam, on the left bank of which is Paramaribo, 300. All are blocked by rapids at various distances from 50 to about 100 miles inland, up to which they are navigable for small vessels, but beyond, only for properly constructed boats that can be drawn through the falls or over portages.