DEEP-SEA EXPLORATION. 59 DEEP-SEA EXPLORATION. vessel was well equipped, and carried a scientific staff under the direction of Sir WjTille Thomson. A jrreat amount of deep-sea work was accom- plished, and the large series of Reports form the most important contribution ever made to the lit- erature of this subject. Other extensive deejj-sea investigations have been conducted at various times by most of the European governments, while vessels of the United States Coast Survey, or of the Fish Commission, have been engaged in them more or less regularly since 1870. The Prince of ilonaco has made very important con- tributions to this department of loiowledge, as he has for many years employed his yachts almost entirely in deep-sea work, and has devoted much time to the improvement of the appliances for investigation. T!ie methods employed by the earlier investiga- tors for measuring the depths were slow and un- certain, for their soundings were made with hemp rope, which was greatly drifted by currents and gave inaccurate depths. The soundings and dredgings conducted on the Challenger were so made, and often imder great difficulties. At the present time such investigations are made by means of wire, the first successful employment of which was by Sir William Thomson in 1S72. Wire sinks rapidly, presents the least frietional surface, and is but little affected by currents; and the machinery is now so perfect that sound- ings may be made with accuracy in the greatest depths. The improved methods show that the early soimdings by the Herald, Congress, and other vessels with rope, supposed to have reached over 7000 fathoms, were erroneous, and that there are probably no such depths in the ocean. The greatest depth kiwicn was discovered by the United States cable-suney ship yero in 1900, near the island of Guam, where a sotmding was made of 5269 fathoms, or nearly six statute miles, a depth sufficient to submerge the highest moun- tains. It is probable that future soundings will reveal slightly greater depths. For four years prior to tlie voyage of the Xero the deepest water known was north of Xew Zealand, where the British ship Penguin sounded in 51.5.5 fathoms. Off the coast of Japan, in 1874, the United States ship Tuscarora found a depth of 4655 fathoms; and in 1900 the United States Fish Commission steamship Albatross made a sounding in the western Pacific of 4813 fathoms. Many great depths have been discovered in the Atlantic, the deepest (4561 fathoms) off Porto P>ieo, by the United States Coast Sur-ey steamer Blake. '^lore than forty 'deeps,' or depressions ranging from 3000 to 5200 fathoms, are now known, some of them mere holes, others of vast extent. Tlie deeps are well distributed over the seas, but none have been foimd north of the fifty-fifth degree of latitude. The average depth of the sea is probably not less than 2200 fathoms. JIethod of SouKDI^•G. In the operation of sounding several instruments are sent down with the wire. A thermometer takes the temperature lit the bottom ; a closing cylinder brings tip a specimen of the bottom water for analysis, and the sounding cylinder at the end of "the line brings up a specimen of the bottom mud or ooze, for examination as to the character of the bot- tom. These instruments are all self-acting at the bottom and are not affected in rising to the surface. To the sounding cylinder is attached the sinker Vol VI.— 5. — a 60-pouud iron shot — which detaches itself on striking the bottom. An indicator attaclied to the reel on deck shows the number of fathoms of wire that have run out. After sounding the wire is reeled in bj- steam. It takes about one hour to make a sounding three miles deep and get the instruments back on board. Deep-Sea Dredgixg. The methods employed on board the United States Fish Commission steamship Albatross, doubtless the best-equipped deep-sea dredger in existence, may be taken as illustrative. The Albatross has brought together larger deep-sea collections than have been made on any other vessel. She has made nearly 6000 hydrographic sotmdings, and nearlj' 2000 hauls of the dredge or beam trawl. The investigations of this vessel cover areas extending from the Banks of Newfoundland along both coasts of North and South America to Bering Sea, and also limited areas in the tropical Pacific, and in the regions between Japan and Kamchatka. Her work lias carried dredging into deeper waters than ever before, animal life having been obt;tined near the Tonga Islands at a depth of 4173 fath- oms, while the dredge on one occasion in Bering Sea brought up from a depth of 1771 fathoms more than 800 deep-sea fishes at a single haul. The creatures of the deep sea are brought up by means of a dredge or beam trawl towed by a wire rope, operated by a powerful engine on deck. The first operation in dredging is to ascertain the depth by sounding, after which the trawl is put overboard and allowed to sink to the bottom as the dredge rope is let out. The dredge, or beam trawl, is simply an iron frame to which is at- tached a strong bag-shaped net about 20 feet long. The mouth of the dredge, as formed by the iron frame, is about eleven feet wide and two feet high. Dragged along the bottom, it quicldy fills with animals. Sometimes it settles into mud or ooze and is very hard to lift. The dredge rope is connected with a large spring, or accu- mulator, attached to the foremast, which often sho«s the dredge to be pulling thousands of pounds. Before the dredge reaches the surface, most of the oozy mud washes away, so that the dredge haul is usually light enough to be hoisted from the water and landed on deck with safety. Sometimes it is filled with fishes; sometimes with sea-urchins, starfishes, crinoids or corals; sometimes with squids and devil-fish. It often brings up a varied collection, in which many classes of marine animals arc represented. The time required by the Albatross in making her deepest dredge haul — that from 4173 fathoms^ was ten hours, the engine reeling in the great weight of line very slowly. In depths of 1000 to 1500 fathoms hauls can be made in three or four hours, according to conditions. In addition to the dredge, another collecting machine, very tiseftil on rough bottom, is the 'tangle.' This consists of bunches of shredded rope attached to iron bars, and when dragged over the bottom it frequently brings up sea- urchins, starfish, and crinoids in abundance. A deep-sea fish-trap has been devised by the Prince of Jlonaco, in which fishes have been taken as deep as two miles. The Albatross, in 1897, suc- ceeded in setting ordinary gill-nets a mile deep, and catching ^lacrurus and other deep-water fishes. Deep-water exploration by means of gill- nets, traps, and trawl lines promises to yield interesting results.
