ORINOCO, Ti'rt-nriki). The smallest of the three great rivers of South America (Slap: Venezuela, D 2). The main stream runs IVI?01 ly within Venezuelan territory, except for a short distance in its middle course, where it forms the boundary between Venezuela and Colombia. It rises on the Parima uplands near the Brazilian frontier. and flows first northwest to the Colom bian boundary, then north into Central Venezue la, and finally eastward until it ernptieP, into the Atlantic Ocean through a large delta beginning near the boundary of British Guiana. The total length of the main stream is 1400 miles. Its course forms a large curve around the edge of the Parima plateau; hence its right banks are generally higher, and the tributaries received from that side smaller, while on the left side are the large plains or Nunes (q.v.), and these are received several tributaries equaling or exceeding the main stream. About 150 miles from its source and 921) feet above sea level the , Orinoco branches, sending one-sixth of its volume into the Cassiquiare, which flows into the Rio Negro, an of of the Amazon. The remainder flows as a navigable river until it is broken by the romantic Maypures and Atures rapids, 870 miles from its mouth. These rapids are the only serious obstruction in the main stream, which below them !lows with a very gentle current over a bed so nearly level that the tides are felt at Ciudad Bolivar, 260 miles from the sea. Thought the e?mntry around the upper courses of the river and its tributaries is heavily forested, the lower reaches traverse open savannas where only the banks are lined with trees, and where the ad jacent country is periodically flooded so that the natives are compelled to live in pile dwell ings. The marshy but heavily forested delta oc
cupies an area of 7000 square miles, and has a eoast line of nearly 200 miles, through which upward of 50 channels enter the ocean. Many of these shift their beds, but seven are per manently navigable for large vessels. The prin cipal navigable tributaries of the Orinoco are the Guaviare, the :Meta, and the (qq.v.), and the total navigable length of the system is 4300 miles. This great waterway, however, is but little used, since the adjacent regions are thinly inhabited, and the great natural wealth practically untouched. In 1000 only one steamer of the Royal Nail Steamship Company plied once every two weeks between Trinidad and Ciudad Bolivar. Smaller steamers continue the service as far as Nutrias on the Apur& hut above the Apur6 confluence there is no regular navigation. Consult: Humboldt, Travels in South America, trans., Bohn Library (London, 1877) ; Chassan jou, L'On'tiogue et le (Paris, 1889) ; Triand, Down the Orinoco in a Canoe (London. 1902) ; Guzman, "La explorachin del in La Espana Moderna, cols clxvi. (Madrid, 1902).