Page:Africa by Élisée Reclus, Volume 3.djvu/36

 uplands throughout the whole year. The other elevated lands on this seaboard also receive a large share of the rainfall, which is nowhere heavier in any part of the Atlantic than in this oceanic region exposed to the influence of the north-east and south-east trade winds between the projecting coasts of West Africa and South America. Tere the still air arrests the rain-clouds brought by both trade winds, the vapours are condensed and precipitated in tremendous downpours on the subjacent waters. In many places this rain water, owing to its less specific

gravity, spreads over the surface in sufficiently thick layers to enable passing vessels to replenish their supply of fresh water.

Although incessantly intermingled by the aërial and marine currents, the waters of the Atlantic basin differ none the less in their degree of salinity not only on the surface, but also in the deeper strata. The most saline is that encircling St. Helena, the specific gravity of which is 1&#x22c5;0285. Owing to the heavy rains a the region of calms the proportion is less in the Guinea Stream, the difference being as much as two or even three thousandths in the north-east part of the