NEGRO, Rio, one of the principal tributaries of the Amazon, rises in New Granada by two head streams, and flows eastwards till it falls into the Amazon, in S. Lat. 3° 16', W. Long. 59°. Its principal affluents are the Cassiquiare, by which it is connected with the Orinoco, the Cababure, Padaviri, and Branco, from the N.; and the Tomo, Zie, Haupes, &c., from the S. and W. In the lower part of its course the river flows through a succession of lakes from 15 to 20 miles broad; at its junction with the Amazon it is about 1½ miles in breadth. The river is flooded during the months of August and September, when it rises about 30 feet above its lowest level. The length is about 1000 miles.