If we examine a chart of the world in the light which has been thrown upon this question by all the reliable soundings obtained up to the present, it will be found that continents and islands which we have been in the habit of considering as separated from each other by wide seas and deep straits virtually form part of the same area of elevation; and, in a similar manner, that certain oceans and seas, which we are accustomed to distinguish by separate names, form part of the same area of depression. It will also appear that, with the exception of the islands scattered over the face of the ocean and of the Antarctic region, all the dry land at present existing may be reduced to one large area of elevation gravitating to the North Pole, as the common centre of the principal land masses; similarly, if we except the Arctic region and other inland basins, all the oceans and seas compose a single vast area of depression, with the South Pole for common centre of the larger accumulations of water on this globe. The Arctic region forms a distinct area of depression placed in the centre of the great area of elevation, and the Antarctic region, according to the evidence we at present possess, is an area of elevation, surrounded on all sides by the above-described great area of depression. The numerous small islands that crop up in the middle of the oceanic basins are generally found associated in groups, and they belong to areas of elevation at the present time submerged, that is to say, in the condition in which we know the dry land to have been at an epoch more or less remote in the history of our planet. In support of the above generalization, we may point to the following facts as established by recent soundings. The 100-fathom line, as is well known, joins the whole of the British Islands, including the Hebrides, Orkneys, and Shetland Islands, to the continent of Europe. It forms a broad band connecting the Asiatic and American continents across Behring Strait. It unites Australia, Papua, and Tasmania in a single area of elevation, which, together with the intervening archipelago of Java, Sumatra, Borneo, Celebes, the Moluccas, and the Philippines, may be looked upon as a prolongation of the continent of Asia. It joins Ceylon to Hindostan and the Falkland Islands to the South American continent. The 500-fathom line connects North America, Greenland, Iceland, the Faroe Islands, and the continent of Europe, the only unexplored space being Denmark Strait, between Iceland and Greenland, where the soundings may exceed the above depth. The 1,000-fathom line unites New Zealand with Australia, Madagascar with Africa, and nearly exhausts the depth of the more or less landlocked seas which lie between Australia and Asia, Africa and Europe, South and North America, and of the seas situated within the Arctic and Antarctic Circles. The Cape de Verde Islands and the Canaries belong to Africa, Madeira to Europe, and less than 500 fathoms divide Norway