Appendix A. 
astronomic studies the city of Alexandria and the commercial emporium of 
Rhapta, lead of themselves to the hypothesis that, besides the details gathered 
from the Greek seafarers along the east coast of Africa, the Alexandrian 
Geographer also utilized the information. obtained in the valley of the great 
river itself. Nor will this assumption appear too bold if we bear in mind that 
long before the time of Ptolemy, the great Eratosthenes, speaking of the chief 
branch of the Nile, expressed himself thus : “ Two waterways fall into the 
Nile : they both come from certain lakes lying far to the east and enclosing a 
very large island known by the name of Meroe. One of these waterways, 
called Astaboras, forms the east side of the island, the other is called Astapus. 
Some authors, however, give to the latter the name of Astasobas, and apply 
the name Astapus to another waterway, which they bring from the lakes lying 
in the region of the south, and regard it in some way as the main stream or 
else as the chief branch of the Nile, adding that its periodical Hoods are due to 
the summer rains.” ( 19 ) If, as seems beyond doubt, the Astaboras is to be 
identified with the Atbara, the Astasobas with the Bahr el-Azrek or Blue Nile, 
and the Astapus with the White Nile or Bahr el-Abiad (main branch of the 
Nile), Ptolemy would have but repeated on the whole what three centuries 
before him had been so well expressed by the Librarian of Alexandria, merely 
adding on his own part the positions—latitude and longitude—of the two 
lakes lying in the region of the south, that is, south of the equinoxial line 
whose waters feed the chief artery of the all-important fluvial system. 
At this point we meet with an apparently serious objection. According to 
the authors alluded to by Eratosthenes the name Astapus is given to the 
principal branch of the Nile flowing from the south, whereas Ptolemj^ applies it 
to an affluent of the Nile which, issuing from Lake Coloe under the equinoxial 
line, falls into the main stream at latitude 12° N. But, as above stated, the 
objection is only apparent. Eratosthenes, speaking for himself, had already 
given the name of Astapus to the river marking the west (and south-west) side 
of the island (peninsula) of Meroe, that is to say, the Abai or Bahr el-Azrek. 
Ptolemy, on his part, did not think it right to depart from the opinion of his 
predecessor, and so kept the name of Astapus for the subordinate river. It 
might lie more important to notice in the Geography of the Alexandrian two 
errors, one of which affects the Lake Coloe (Lake Tana or Tsana in the heart 
of Abyssinia), which he places under the equinoxial line. The other mistake 
consists in describing the Astaboras as a river which mingles its waters with the 
Astapus. But an enquiry into all these matters, besides requiring too great a 
development, would be foreign to the question of the lakes, sources of the Nile, 
and to that of the Mountains of the Moon. Notice can only be taken of the 
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