OCEANIC INTERCOMMUNICATION It is scarcely necessary to draw the attention of the student to the importance of a clear conception of the actual and relative position of the great oceans and minor seas. This, in fact, is indispensable ; otherwise, no matter what amount of information may be acquired, it will be more or less vague and indefinite. The mutual relations of the more important parts of the "world of waters," may perhaps be most easily and clearly perceived by a systematic consideration of what we have ventured to call " oceanic intercommunication." Let us then proceed to observe, first, how the great oceans communi cate with one another ; and, secondly, the connection between each ocean and the minor seas, &c., belonging to it.
The Atlantic Ocean, lying between the two greatest longitudinal expanses of land, is open only on the north and south. On the north it communicates with the Arctic Ocean by two channels of unequal width ; Davis Strait, between Cumberland Island and Western Greenland, and the wider channel between East Greenland and Norway. But while communication northwards is thus comparatively limited, the South Atlantic opens out broadly into the Antarctic Ocean. At 35° S. lat. the definite boundary formed by the African coast ceases ; thence to the Antarctic an imaginary line, along the line of 20° W. long., forms the theoretical limit between the Atlantic and Indian Oceans. Thus the com munication on the east with the Indian Ocean is perfectly open for 31i degrees. We may also remark that there is now actual communication between the Atlantic and Indian Ocean by the Mediterranean, Suez Canal, and the Red Sea. The western side of the South Atlantic is definitely limited by the South American coast as far as S. lat., and a line drawn thence along the meridian of Cape Horn to the Antarctic Circle forms an imaginary boundary between the South Atlantic and Pacific Oceans, which thus commu nicate by the channel between Tierra del Fuego and South Shetland, as well as by Magellan's and other straits between the islands of Tierra del Fuego.
The limit (the Antarctic Circle) between the South Atlantic and the Antarctic Ocean is, of course, purely imagin ary, there being only one natural boundary—Graham Land.
With this exception the communication between the Atlantic and Antarctic is perfectly open, the one merging indefinitely into the other. Besides the channel already referred to, there is no direct communication between the Atlantic and the Pacific Ocean. Hence the expeditions sent out to discover a "north west passage" into the Pacific through some of the numerous channels in the Arctic Archipelago. Captain McClure solved the problem in 1850, but the generally icebound state of the channels by which alone the passage can be made has rendered the discovery practically of no value. The narrowness of the isthmus connecting North and South America induced the idea of joining the two oceans by a canal, which will most probably be made before long.
The communication between the minor seas belonging to the Atlantic and the ocean itself is generally good—the channels in each case, though often of no great width, being sufficiently deep to allow the passage of the largest vessels. It must be borne in mind that the inland seas, &c. mentioned in this paragraph, belong entirely to the North Atlantic, thew being no inland ramifications of the. South Atlantic, nor even any considerable indentation, except the Gulf of Guinea.
Between Great Britain and the north-western coasts of the Continent lies the North Sea or German Ocean, connected with the Atlantic directly on the north, and indirectly on the south, by means of the English Channel. The North Sea is also connected with the Baltic by the Cattegat and the Skager Rack. The Irish Sea, between Ireland and the opposite Scotch and English coasts, is connected with the Atlantic on the north by the North Channel, and on the south by St. George's Channel. The Straits of Gibraltar admit of direct communication between the Atlantic and its largest inland sea—the M edit err anean,—which is again connected with the Black Sea by the Dardanelles, Sea of Marmora, and the Bosphorus, and, by means of the canal across the isthmus of Suez, with the Red Sea, and thus with the Indian Ocean.