The recording of travellers’ tales as to the twin lake sources of the main Nile stream and the existence of a great snowy range called the Mountains of the Moon was not the only contribution made by Claudius Ptolemæus to Nile geography. The Egyptian Greek indeed was a geographical giant compared with any of his predecessors, nor was the height of his knowledge concerning the geography of Europe, Asia, and Africa reached and passed until the fifteenth century of the present era, some twelve hundred years after his death. The results of the later Crusades, intercourse with the Arabs, and the journeys of Marco Polo and other enterprising Venetians had brought in some cases confirmation of Ptolemy’s theories, had corrected some of his errors, and had filled up gaps in his information. But as regards the geography of Africa more especially, Ptolemy remained ostensibly the great authority until the end of the fifteenth century, although, as already mentioned in a footnote, the latest editions of Ptolemy’s maps (the latest ascribed to Ptolemy was published about 1485) show that the geographers at the closing part of the fifteenth century, consciously or unconsciously, touched up Ptolemy’s work by later information received from Arabs, Italians, and Turks. Ptolemy discussed with much detail the whole course of the Nile so far as it lay to any extent within the regions of the known. He described the approximate outline of its course about as far as the present site of Berber, which district he describes as the Greater Primis, a name which Sir E. H. Bunbury takes to be identical with the locality of Primnis[7] rumoured by Strabo. Above this point Ptolemy applies the name of Meroe (so often attributed to settlements or districts in Dongola) to that great peninsula which is so nearly enclosed between the Atbara, the main and the Blue Niles. Ptolemy indeed, and most writers of earlier and later days, believed this district to be an actual island.[8] The junction of the Blue and the White Niles is wrongly placed by Ptolemy in latitude 12° north, instead of 15° 40′, and from this point southwards Ptolemy’s proposed latitudes of places on the White Nile became increasingly incorrect, so that by him the Nile system was carried a little too far to the south of the equator. South of the site of modern Khartum Ptolemy had but little information to go upon, other than the account of the Centurions’ voyage; but from such suggestions as he could obtain, together with the story of Diogenes, he guessed that the twin sources of the White Nile joined their streams into one river at 2° north latitude. This junction described with the knowledge of later days would be equivalent to the exit of the Nile from Lake Albert, the real latitude of this point being 2° 25′--an uncommonly good guess on Ptolemy’s part. Ptolemy, however, imagined nothing quite like Lake Albert, but thought that the waters coming respectively from