(or Surinam), from the Corentyn to the Maroni river; French
Guiana (or Cayenne), from the Maroni to the Oyapock river;[1]
Brazilian (formerly Portuguese) Guiana, extending from the
southern boundaries of French, Dutch, British and part of
Venezuelan Guiana, to the Amazon and the Negro. Of these
divisions the first and last are now included in Venezuela and
Brazil respectively; British, Dutch and French Guiana are
described in order below, and are alone considered here.
In their physical geography the three Guianas present certain common characteristics. In each the principal features are the rivers and their branch streams. In each colony the northern portion consists of a fluviomarine deposit extending inland and gradually rising to a height of 10 to 15 ft. above the sea. This alluvial plain varies in width from 50 m. to 18 m. and is traversed by ridges of sand and shells, roughly parallel to what is now the coast, indicating the trend of former shore lines. By the draining and diking of these lands the plantations have been formed along the coast and up the rivers. These low lands are attached to a somewhat higher plateau, which towards the coast is traversed by numerous huge sand-dunes and inland by ranges of hills rising in places to as much as 2000 ft. The greater part of this belt of country, in which the auriferous districts principally occur, is covered with a dense growth of jungle and high forest, but savannahs, growing only a long wiry grass and poor shrubs, intrude here and there, being in the S.E. much nearer to the coast than in the N.W. The hinterlands consist of undulating open savannahs rising into hills and mountains, some grass-covered, some in dense forest.
Geology[2].—Guiana is formed almost entirely of gneiss and crystalline schists penetrated by numerous dikes of diorite, diabase, &c. The gold of the placer deposits appears to be derived, not from quartz reefs, but from the schists and intrusive rocks, the selvages of the diabase dikes sometimes containing as much as 5 oz. of gold to the ton. In British Guiana a series of conglomerates, red and white sandstone and red shale, rests upon the gneiss and forms the remarkable table-topped mountains Roraima, Kukenaam, &c. The beds are horizontal, and according to Brown and Sawkins, three layers of greenstone, partly intrusive and partly contemporaneous, are interstratified with the sedimentary deposits. The age of these beds is uncertain, but they evidently correspond with the similar series which occurs in Brazil, partly Palaeozoic and partly Cretaceous. In Dutch Guiana there are a few small patches supposed to belong to the Cretaceous period. Along the coast, and in the lower parts of the river valleys, are deposits which are mainly Quaternary but may also include beds of Tertiary age.
History.—The coast of Guiana was sighted by Columbus in 1498 when he discovered the island of Trinidad and the peninsula of Paria, and in the following year by Alonzo de Ojeda and Amerigo Vespucci; and in 1500 Vincente Yañez Pinzon ventured south of the equator, and sailing north-west along the coast discovered the Amazon; he is believed to have also entered some of the other rivers of Guiana, one of which, now called Oyapock, is marked on early maps as Rio Pinzon. Little, however, was known of Guiana until the fame of the fabled golden city Manoa or El Dorado tempted adventurers to explore its rivers and forests. From letters of these explorers found in
- ↑ This is the boundary generally accepted; but it is in dispute.
- ↑ See C. B. Brown and J. G. Sawkins, Reports on the Physical, Descriptive and Economic Geology of British Guiana (London, 1875); C. Velain, “Esquisse géologique de la Guyane française et des bassins du Parou et du Yari (affluents de l’Amazone) d’après les explorations du Dr Crevaux,” Bull. Soc. Géogr. ser. 7, vol. vi. (Paris, 1885), pp. 453-492 (with geological map); E. Martin, Geologische Studien über Niederländisch-West-Indien, auf Grund eigener Untersuchungsreisen (Leiden, 1888); W. Bergt, “Zur Geologie des Coppename- und Nickerietales in Surinam (Hollandisch-Guyana),” Samml. d. Geol. Reichsmus. (Leiden), ser. 2, Bd. ii. Heft 2, pp. 93-163 (with 3 maps); and for British Guiana, the official reports on the geology of various districts, by J. B. Harrison, C. W. Anderson, H. I. Perkins, published at Georgetown.
