[COPYRIGHTED] U. S. NAVAL INSTITUTE, ANNAPOLIS, MD. THE PHYSICAL CHARACTERISTICS OF THE By G. W. LITTLEHALES As a result of the marine hydrographic coast surveys of the various maritime countries, undertaken in the interests of navigation, the coast line of the world is now among its best known geographical features, and hence, since geodesists have determined the size of the terrestrial spheroid, the area of the oceanic surface of the globe is known with closeness to be 140 million square statute miles, which is an expanse exceeding the total area of the lands of the globe by 83 million square statute miles. In other words, 71 per cent of the surface of the globe is covered by the waters of the ocean. Although the depth of the ocean has been measured in many thousand places throughout the world, since the middle of the nineteenth century when deep-sea soundings first began to be successfully made, yet, as will be seen from the accompanying world-chart showing where the ocean has been sounded, there are oceanic areas as large as the United States where no soundings have been taken, and many others where the present soundings are but widely spaced. The contours of the oceanic basins cannot, therefore, be completely drawn at present, and the volume of the ocean may only be stated by estimation to be 324 million cubic statute miles, or 14 times the bulk of all the lands in the world above sea level: The accepted measurements of the areas within the different zones of depth are shown in the diagram on page 46. The mean depth of the ocean is estimated to be 2080 fathoms; and the greatest depth, which is found east of the Island of Mindanao, is 5348 fathoms. In their general extent and position, it is likely that ocean basins have been permanent since the waters were gathered together. The study of deep-sea observations does not support the view that, by alternate rising and sinking of the earth's crust, oceans and continents have successively occupied the same areas. All known chemical elements have been found in the waters of the ocean, and if there are any that are unknown, they will also be found there. Although the total amount of salts contained in sea water varies in different parts of the ocean, the existing proportions set forth in the following table, according to Dittmar's 5500 Fathoms 60% 70% 802 902 100% 20% 30% 40% 50% DIAGRAMMATIC SECTION SHOWING THE AVERAGE CONTOUR OF THE LITHOSPHERE, BASED UPON THE PERCENTAGES OF THE AREAS BETWEEN THE CONTOURLINES ABOVE AND BELOW SEA-LEVEL. analysis, are practically the same in all parts and at all depths of the open ocean: The dissolved substances are present mainly as ions. Of the elements in solution, sodium and chlorine seem to be the only ones that are not withdrawn by organisms and organic processes, |