DEEP-SEA EXPLORATION. 



741 



DEEP-SEA EXPLOKATION. 



vessel was well equipped, and carried a scientific 

 staff under the direction of Sir Wyville Thomson. 

 A great 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 deep-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 Monaco has made very important con- 

 tributions to this department of knowledge, 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. 



The 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 under 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 1872. 

 Wire sinks rapidly, presents the least frictional 

 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 soundings 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 known was discovered by 

 the United States cable-survey ship Nero in 1900, 

 near the island of Guam, where a sounding 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 the voyage of the Nero the deepest water 

 known was north of New Zealand, where the 

 British ship Penguin sounded in 5155 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 Kico, by the 

 United States Coast Survey steamer Blake. More 

 than forty 'deeps,' or depressions ranging from 

 3000 to 5200 fathoms, are now known, some of 

 them mere holes, others of vast extent. The 

 deeps are well distributed over the seas, but 

 none have been found north of the fifty-fifth 

 degree of latitude. The average depth of the sea 

 is probably not less than 2200 fathoms. 



Method op SouNpiNG. In the operation of 

 Bounding several instruments are sent down with 

 the wire. A thermometer takes the temperature 

 at the bottom; a closing cylinder brings up 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 ooza, 

 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 



— a 60-pound iron shot — which detaches itself on 

 striking the bottom. An indicator attached to 

 the reel on deck shows the number of fathoms of 

 wire that have run out. After sounding the wire 

 is reeled in by steam. It takes about one hour to 

 make a sounding three miles deep and get the 

 instruments back on board. 



Deep-Sba Drbdgins. The methods employetd 

 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 soundings, and nearly 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 has carried dredging into deeper waters 

 than ever before, animal life having been obtained 

 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 quickly 

 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 

 shows 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 are represented. The 

 time required by the Albatross in jnaking her 

 deepest dredge haul — that from 417? 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 useful on rovigh 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 Monaco, 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 Macrurus and other deep-water 

 fishes. Dpop-water exploration by means of gill- 

 nets, traps, and trawl lines promises to yield 

 interesting results. 



