ERATOSTHENES-^PTOLEMY. 
387 
course ; its reception, on the eastern side, of two 
great rivers arising from lakes, and called the 
Astaboras and the Astapus, of which the latter 
flows from lakes in the south, is swelled to a 
great height by the summer rains, and forms then 
almost the main body of the Nile. He describes 
also the bend which it makes in its passage 
through Nubia. The source of this great stream 
being conceived to lie in these regions rendered 
inaccessible by extreme heat, was considered as 
beyond the reach of discovery. The idea, how- 
ever, of its coming from the west still prevailed ; 
and Strabo mentions a report of its flowing from 
the remote boundary of Mauritania. This idea is 
followed at greater length by Mela and Pliny, 
whose speculations on the subject will find a plac^ 
in the following chapter. 
Equal in fame with the geographical school of 
Eratosthenes, was that of Ptolemy, who did not, 
however, flourish till the second century of the 
Christian era. This school displays a great acces- 
sion of actual knowledge with regard to all the 
remote quarters of the world ; yet this, in many 
instances, was by no means accompanied with 
sounder views as to those parts which lay still 
beyond the sphere of observation. It was ascer- 
tained, that the bounding ocean of Asia did not 
exist at the point fixed by Eratosthenes ; hence it 
