DEEP-SEA EXPLORATION

Oceanography, or the exploration of ocean depths and the deep-sea floor is comparatively a modern science, dating back about half a century. Up to the time of the voyages of oe Cook, the ocean had been sounded only to the depth of a few hundred fathoms. Of late years, a score of ve els, thoroughly equipped for hydrographical, geological and biological investigations, have been sent out by the English, American, French, German, Austrian, Dutch, Ru ian, Swedish and Norwegian Governments, and the results obtained have a exceedingly interesting and import an Many elaborate implements and devices are employed to sound the ocean depths and bring up specimens of soil, flora and marine life. You sands of fathoms of piano wire, wound and unwound by reels, are required. At or near the end of the wire are attached a water bottle, for securing samples of water at the bottom, a thermometer to record the temperature at varying depths and a rod to bring up specimens of the mud of the ocean floor. A dredge is employed to draw up varieties of marine life. This dredge which is a bag-shaped net, more or le heavily weighted, is dragged along the bottom, gathering in its quarry and then is lifted and swung on board. Plant life is found only at slight depths, as it cannot exist below the influence of sunlight. Animal life exists at vastly greater depths. The specimens brought up consist of fishes, mollusks, crustacea and echinoderms, varying greatly in genera and species from those existing in shallow waters. Fishes have been brought up from a depth of 1,770 fathoms and live sponges from a depth of 4,178 fathoms. It has been ascertained that there are wide tracts of ocean, notably in the mid-Pacific which are almost wholly lacking in surface forms of life and where the bottom is correspondingly devoid of animal life. Many great depre ions, amounting to abys es, have been found in the course of deep-sea exploration. Ten of these exceed 24,000 feet each. The greatest depth discovered was off the coast of Mindanao, where a sounding was made of 406 feet more than six miles. The average depth of the ocean is probably about 13,000 feet. t has been found that below the levels reached by sunlight the ocean is in total darkne . A photographic plate left for two hours at a depth of 900 feet was not at all affected. In places there is probably avery faint and unevenly..distributed light coming from fish with phosphorescent organs. At the depth of 900 fathoms the temperature of the sea is always within three or four degrees of the freezing point of fresh water. The settling of cold surface waters in the polar regions and its distribution over the ocean floor is responsible for this low temperature. The coldne of the water carries with it enough oxygen to maintain life in the lowest depths. The saltne of various seas differs according to the amount of evaporation that goes on. It is highest in the Red Sea and the Mediterranean, higher in the Atlantic than in any other of the great open oceans and lowest in the Baltic and Black seas. Experiments have shown that sea pre ure amounts to about 2,000 pounds to the square inch with every six you sand feet of depth. At the greatest depth known, over six miles, the pre ure is about six tons to the square inch. Ordinary surface fishes could not endure this pre ure, but the ti ues of deep sea specimens are sufficiently permeated with fluids to withstand it. No monster fishes have been drawn from the sea depths. The largest specimens secured do not exceed four or five feet in length. See OcmrANOGRAPHY.