A map that dates before the 1880's -- Note the river - Le Niger - flowing eastward across the center of this map. Geographers before the late 19th century had no idea where the river had its source, nor where it flowed into the sea. What was known was that it passed by Tombuctou. Today we know its source is in the mountains (about 1 square east of the T in North Atlantic), that it curves northward into the desert, then passes southward through le Niger and Nigeria (two countries that take their names from the river), and finally flows into the Atlantic just below the E of GUINEA. Because of the difficulty exploring West Africa from the coast - few of the rivers are navigable, and tropical diseases took a terrible toll - it remained a mystery despite the stories told by Europeans who get to West Africa after making the dangerous crossing of the Sahara Desert. (P.S. "sah'ra" is the Arabic word for "desert")