Nyassa, a lake in S. E. Africa, with its S. extremity situated about 350 m. W. of the town of Mozambique, in lat. 14° 25' S., lon. 35° 10' E., whence its waters are known to extend northward upward of 200 m. The width of the main body of water varies from 20 to 60 m. The southern portion consists of two arms, between which rises Cape Maclear, a lofty headland with its summit 2,000 ft. above the surface of the lake. From the S. extremity of the eastern arm flows the river Shire, which joins the Zambesi about 90 m. from the sea. This arm of the lake is about 30 m. long and from 10 to 12 m. wide, while the length of the western arm is not more than half as great. According to Dr. Kirk, the elevation of Nyassa above the level of the sea is 1,522 ft. The country on both sides is mountainous. The lake is known to be very deep, in some places over 40 fathoms; and its clear, blue waters are frequently lashed into waves of extraordinary magnitude by the sudden and violent storms to which it is subject.

Both the E. and W. banks are populated, and the latter has been explored nearly to lat. 11° S.; but, so far as known, the northern extremity has never been visited by any European. Nyassa was first laid down on Portuguese maps as early as 1546, but no precise information concerning its position was obtained until the time of Manoel Godinho (1663), who learned in India from a Portuguese traveller that it communicated with the Zambesi through a river which he called Zachaf. In 1859 it was doubly discovered: on Sept. 16 by Dr. Livingstone, who reached it through the valley of the Shiré; and on Oct. 19 by Dr. Albrecht Roscher of Hamburg, who was attacked by two of the natives on the E. shore and killed by poisoned arrows, shortly after making his way to the lake from Kilwa. Nyassa has since been explored, in 1861 by Livingstone and Kirk, in 1863 and 1866 again by Livingstone, and in 1867 by Mr. E. D. Young.