ROHLFS, Gerhard, a German traveller, born at Vegesack, near Bremen, April 14, 1834. He studied medicine at Heidelberg, Würzburg, and Göttingen, went to Algeria, enlisted in the foreign legion of the French army, served in the conquest of Kabylia, and attained the highest rank open to a foreigner. Having there learned the Arabic language and the mode of life of the inhabitants, in 1861 he went to Morocco, where in the character of a Mohammedan physician he acquired the friendship of the grand sherif, and under his protection travelled through the country, traversing the Morocco portion of the Sahara from W. to E., and exploring the whole course of the wady Draa. On this journey he was treacherously attacked by his guides, robbed, and left for dead in the desert, with a broken arm. In 1864 he travelled still further in Morocco, and crossed the Atlas mountains to the oasis of Tuat. His description and map of the country were the first ever made from personal observation and with scientific knowledge. After a short visit to Germany in 1865 he returned to Africa, and traversed the continent disguised as an Arab from Tripoli to Lagos, by way of Moorzook in Fezzan, Bilma, Kuka, the chief city of Bornoo, the river Benoowe, the Niger, and the Gomba country. The journey occupied altogether about two years, and obtained him the medal of the royal geographical society of London. Rohlfs's detailed account of it is contained in the Ergänzungsheft No. 34 to Petermann's Geographische Mittheilungen (Gotha, 1872). At the close of 1867, by order of the king of Prussia, he joined the English expedition against Abyssinia. He returned to Tripoli in 1868, and in 1869 traversed the desert from Tripoli to Alexandria, visiting the oasis of Siwah, the ancient Ammonium. In 1873, with an expedition of 100 camels and 90 men, organized under the patronage of the khedive of Egypt, he explored the Libyan desert W. of the chain of oases which skirt the valley of the Nile, and discovered that the depression called the Bahr Bela-ma (river without water) marked on many maps of the desert does not exist. The progress of the expedition S. W. of the oasis of Dakhel was stopped by hills of loose sliding sand, which the camels were unable to traverse; and in lat. 25° 11' N., lon. 27° 40' E., the party turned back. In 1875 he visited the United States, and lectured on his travels. His most important publications are: Reise durch Marokko (2d ed., Bremen, 1869); In Abessinien (1869); Von Tripolis nach Alexandria (1871); Mein erster Aufenthalt in Marokko (1873); Quer durch Afrika: Reise vom Mittelmeer nach dem Tschad-See und zum Golf von Guinea (Leipsic, 1874 et seq.); and Drei Monate im libyschen Wüste (Cassel, 1875 et seq.). Winwood Reade edited his “Adventures in Morocco and Journeys through the Oases of Draa and Tafilet” (London, 1874).