Page:Africa by Élisée Reclus, Volume 3.djvu/38

 their domain from the Arctic to the Antarctic Ocean, but it is very different with the cetaceans and other animals confined more to the surface waters. Thus the southern whales, till recently very numerous in the tracts stretching west and south-west of the Cape of Good Hope as far as the small Tristam da Cunha Arychipelago, never reach the latitude of St. Helena. According to Maury's expression, they are arrested by the tepid tropical waters as by a "wall of flames." The Lusitanian and Mediterranean species in the same way diminish gradually southwards, as do also those of the West Indies. Nevertheless, a large number of the latter are still met in the neighbourhood of Ascension, in the very centre of the South Atlantic. About the river mouths again animal life is much more abundant than in the open sea. As we approach the Congo estuary the number of fishes inhabiting the surface waters steadily increases, causing a corresponding increase of the phosphorescence visible at night, notwithstanding the diminution of salinity caused by the great volume of fresh water discharged by the Congo.