378 
GEOGRAPHICAL SYSTEMS 
Another hypothesis, eminently characteristic of 
this school, was probably suggested by African 
phenomena. This was the existence of an unin- 
habitable torrid zone. To those who saw this con- 
tinent, even north of the tropic, spread into an ex- 
panse of burning sand, which reflected a heat scarce- 
ly compatible with animal life, it naturally appeared 
that an exposure to the sun's still more powerful 
influence must be inevitably fatal. The borders 
of the desert would probably have been fixed as the 
point, beyond which life could not pass. But the 
long course of the Nile, and the celebrated king- 
dom of Ethiopia, proved the necessity of looking 
still higher. Upon the Nile, therefore, they mea- 
sured the habitable world of Africa, and fixed its 
limits at the highest known point to which that 
river had been ascended. This is assigned about 
three thousand stadia (three or four hundred 
miles) beyond Meroe, # which does not give the 
fifty-two days' sail of Herodotus, so that it would 
appear as if the Nile had been traced to a higher 
point in his time, than in that of Eratosthenes. 
The latter, however, shews himself intimately ac- 
quainted with the details of its early course ; its 
reception, on the eastern side, of two great rivers 
arising from lakes, and called the Astabaras and 
the Astapus, of which the latter flows from lakes 
* Lib. II. p. 65. (ed. Casaubon.) 
