CHAP. XYITI.] 
PTOLEMY’S THEORY. 
475 
and that it issued from it; thus they were correct in 
all their investigations, which my discoveries have 
confirmed. Their general description of the country 
was perfect, hut not having visited the lake heard of 
as the Luta N zige, they could not possibly have been 
aware of the vast importance of that great reservoir in 
the Nile system. The task of exploring that extraor¬ 
dinary feature having been accomplished, the geo¬ 
graphical question of the sources of the Nile is explained. 
Ptolemy had described the Nile sources as emanating 
from two great lakes that received the snows of the 
mountains in Ethiopia, There are many ancient maps 
existing upon which these lakes are marked as positive : 
although there is a wide error in the latitude, the fact 
remains, that two great lakes were reported to exist 
in equatorial Africa fed by the torrents from lofty 
mountains, and that from these reservoirs two streams 
issued, the conjunction of which formed the Nile. The 
general principle was correct, although the detail was 
wrong. There can be little doubt that trade had 
been carried on between the Arabs from the Red Sea 
and the coast opposite Zanzibar in ancient times, and 
that the people engaged in such enterprise had pene¬ 
trated so far into the interior as to have obtained a 
knowledge of the existence of the two reservoirs ; thus 
may the geographical information originally have been 
brought into Egypt. 
The rainfall to within 3° north of the equator extends 
over ten months, commencing in February and ter¬ 
minating in the end of November. The heaviest rains 
fall from April till the end of August; during the 
latter two months of this season the rivers are at 
their maximum : at other times the climate is about 
as uncertain as that of England; but the rain is of 
the heavy character usual in the tropics. Thus the 
rivers are constant throughout the year, and the 
Albert Lake continues at a high level, affording a 
steady volume of water to the Nile. On the map given 
to me by Captain Speke he has marked the Victoria 
