Congo, Or Zaire, the largest river of western Africa S. of the Niger. It has also been called the Barbela, but the native appellation is Moienzi Enzaddi, " the great river," or "the river that absorbs all other rivers." Its source is unknown, but tradition among the natives places it in a marsh situated near the equator, about lon. 18° E. It flows into the Atlantic ocean near Point Padron, near lat. 6° S., lon. 13° 30' E., and is from 7 to 10 m. wide and more than 160 fathoms deep at its mouth, with a velocity of between 4 1/2 and 5 knots an hour. The Congo has been ascended by Europeans to a distance of 280 m. inland. In the lower part of its course it exceeds 5 m. in width, and, with the exception of a portion called the narrows, maintains a breadth varying from 1 to 4 m. throughout its whole known extent. The narrows extend some 40 m. above a point 140 m. from the coast, where the tide is still perceptible, causing a rise and fall of from 12 to 16 inches. Here the river flows turbulently between steep banks of rock not more than 500 yards apart, and is obstructed by rapids and the so-called Yellala, or cataract, of which the fall, however, is only 30 ft. in 1,500. Geographers estimate that the Congo drains an area of 800,000 sq. m.

Regarding the depth of the river as 60 ft. and its breadth as 9,000 ft., which are believed to be fair approximations, the outflow of water is 1,800,000 cubic feet per second. This is greater than that of the Mississippi.

Between the cataract and the sea not a single tributary falls into the river on either side. Near the coast the stream is studded with islands, and the adjacent country is low, level, and swampy, abounding in mangrove growths. Further inland hills rise parallel to the banks, and not far from them, to a height of 2,000 ft. The vegetation of the valley is for the most part exceedingly luxuriant. The river forms the N. boundary of the kingdom of Congo, which it separates from Loango. It was once thought to be the outlet of the Niger. The German geographer Petermann regards it as identical with the great river Lualaba recently discovered by Livingstone in central Africa, and hence as connected with the vast lacustrine system of the equatorial region. Capt. J. K. Tuckey of the British navy, who explored it in 1816, then expressed the opinion that "the Zaire will be found to issue from some large lake or chain of lakes, considerably to the northward of the line."Further explorations of the Congo by scientific expeditions from Europe are now (1873) in progress.