APPENDIX, 
Ixxxiii 
side, during the periodical season of the S W winds ; which corresponds in 
all its cig:umstances with the same monsoon in India.* 
To the north of this belt, with the exception of the Egyptian Nile, the 
•waters conform generally to the direction of the high land ; passing at no 
great distance (comparatively) from its base, to the right and left : as if the 
surface of the Sahara had a general dip to the southward.t These rivers, 
moreover, receive all their supplies from the south ; no streams of any bulk 
being collected in the Desert. ^ 
In order to produce this efiFect, there must necessarily be a vast hollow in 
the interior of Africa, between the high land of Nubia on the east, and Man- 
ding on the west ; and of which the mountains and Desert form the other 
two sides. Nor is this state of things unexampled in the other continents. 
In Asia, the hollow, to whose waters the Caspian and Aral serve as recipients, 
is no less extensive than the one just mentioned ; reckoning from the sources 
of the Wolga to those of the Oxus; (which latter has ever communicated 
with the Caspian, either throughout the year, or during a part of it :) the diffe- 
rence is, that in Asia, a greater portion of the hollow is filled up with water, 
than in Africa. 
The THIRD part is of course, the Great Desert (or Sahara), and its mem- 
bers; consisting of the lesser deserts of Bornou, Bilma, Barca, Sort, &c. 
This may be considered as an ocean of san d,+ presenting a surface equal 
in extent to about one half of Europe y and having its gulfs, and bays; as 
also its islands, fertile in groves and pastures, and in many instances con- 
taining a great population, subject to order and regular government. The 
* A ridge stretches to the south, through the middle of South Africa, and forms an, 
impenetrable barrier between tlie two coasts. M. Correa de Serra informs me, that 
the Portugueze in Congo and Angola, have never been able to penetrate to the coast of 
the Indian ocean. 
Mr. Bruce learnt (Vol. iii. p. 668.) that a high chain of mountains from 6' runs south- 
ward thro'jgh the middle of Africa, He supposes the gold of Sofala to be drawn front 
these mountains, (p. 669.) 
f Circumstances have shewn, that it declines to the eastward also. 
t " A wild expanse of lifeless sand and sky 1'* TbomsoHi, 
u 
