Page:Africa by Élisée Reclus, Volume 3.djvu/20

 cables have been deposited. In the same way the existence of an identical organic life in the stratified Miocene rocks of Nebraska and Europe shows that, notwithstanding their present distinct faunas and floras, these two regions at one time formed continuous land. How often during the physical history of the globe has the relief of the continents thus been modified, mere passing forms which arise and vanish like the clouds in the heavens!

Yet who shall relate all the vicissitudes of land and water in the valley of the tropical Atlantic even since Jurassic times? The Azores, Madeira, the Canaries, the Cape Verd archipelago, may themselves possibly be surviving fragments of the continental mass that once filled this oceanic region. They are at all events disposed like a border range skirting a semicircular shore, describing a regular arc, in the same direction as the Central Andes of Peru and Bolivia, and the volcanic system of North America, from Mount St. Elias to the Californian Shasta. These Atlantic groups consist almost entirely of igneous rocks and volcanic cones, like those American border ranges. Hence, if the conjecture be true that craters occur along the lines of fracture from the marine shores, all these archipelagoes would indicate the outlines of the ancient coast of a geological Atlantis. They also greatly resemble each other in their general constitution, forming altogether a distinct group amongst the physical regions of the globe.

These Atlantic archipelagoes are not physical dependencies of the African continent, as might be supposed from a cursory view of the maps. Doubtless most of them lie relatively close to the mainland; but the intervening oceanic depths, hitherto supposed to be inconsiderable, are, on the contrary, now found greatly to exceed 3,000 feet, while a complete separation is established by the contrasts in the respective faunas and floras. In many respects these archipelagoes form an inter- mediate domain between three worlds. In climate and products the Azores, Madeira, and even the Canaries, belong rather to Europe than to the neighbouring African mainland. Through their first known inhabitants the Canaries formed part of the Berber world, that is, of North Africa; lastly, many of their vegetable species have been brought by the Gulf Stream from the American continent. Historically, also, these groups formed natural zones of transition, serving as links in the discovery of the New World. Even still, Saint Vincent, a member of the Cape Yerd group, is the chief shipping station between Europe and Brazil, while the more densely peopled islands in the Azores and Canaries are so many gardens of acclimatisation for the plants introduced across the Atlantic from the surrounding continents.

The oceanic tract above which rises the Azores archipelago, should be more specially named the Atlantic, for these are the waters which, stretching due west from the- Atlas and Pillars of Hercules, were frequented by the seafarers of antiquity. But this expression, Atlantic, that is, "Sea of the Atlas," has gradually been extended to the whole depression separating the Old and New Worlds, from the Frozen Ocean to the Antarctic lands. If no clear natural division can be