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Proceedings of the Royal Society 
4. The Nature of the Surface of the Lake Region—Its Great Fertility. 
Africa, the only one of the continents which has a large extent 
of land on each side of the equator, presents a series of zones, each 
of which has a different nature of surface, and these belts correspond 
very closely with one another on the opposite sides of the equator. 
The central area of Africa, below the equator, in the zone of long 
rainy seasons, or of almost constant rain, is a region characterised 
by dense forests, and a most luxuriant overgrowth of vegetation, 
comparable to that of the selvas of the Amazon River in South 
America, which occupy the same equatorial position on the globe. 
To north and south of this forest zone is a belt of less wooded 
country, merging gradually into open cultivated or pasture lands. 
Next, these grass lands pass into the two great almost rainless 
deserts of the Sahara in the north, and of the Kalahari southward. 
Beyond the deserts, at the extremities of the continent, the outer 
slopes of the Cape Colony in the south, and of the plateau of 
Barbary, the “ Tell ” country, in the north, present a second zone 
of fertile and cultivated country. 
The Lake Region extends from this central forest zone, in which 
the equatorial lakes are formed, through the more open belt of less 
wooded country southward, as far as the Zambezi valley, and this 
area is almost everywhere adorned with the choicest natural 
varieties of shady forest, with luxuriant underwood, or clumps of 
trees with rich grassy plains between. 
5. Climate of the Lake Region. 
Nowhere more than in this central region of Africa are the sub¬ 
jects of temperature, rain, and winds, more closely interwoven, or 
mutually dependent, the one upon the other. In the passage of 
this area beneath the sun, a low atmospheric pressure is produced 
by an ascending heat column, and by the condensation of vapour in 
this; the winds flow into the ascending column, and bring with 
them the moist air of the ocean, which, condensing in copious 
floods of rain, reduces the temperature, whilst causing a further 
opening, into which the winds blow with increased power. The 
area of low pressure, with its attendant circumstance of winds and 
rains, always tends towards that part of the continent which is 
