Rio Negro, 1, One of the larger tributaries of the Amazon, rises as the Guainia in SE. Columbia; crosses Venezuela and Brazil in a more or less SE. direction, and joins the Amazon (the Marañon here) near Manaos after a course of 1350 m.; some of its tributaries connect the Orinoco with the Amazon. 2, Has its source in a small lake in the Chilian Andes, flows NE. and E. to the Atlantic, is some 500 m. long, and easily navigated.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Rio Grande do Sul * Rioja