DEPTH OF THE OCEAN. 633 



per 1,000 fathoms, and the sinker 50 lbs. A dial records the number of 

 fathoms paid out. 



A few figures will suffice to show the great superiority of wire over 

 hemp sounding-line. In H.M.S. Challenger, a hemp line, with a sinker 

 of 4 cwt., was used, and in the International, a wire line, O'OS inch in 

 diameter, with a sinker of 50 lbs. In a depth of 2,435 fathoms, the hemp 

 line took 33 minutes to sink, and 2^ 2" to haul up. In 2,929 fathoms, 

 the wire took 29™ 45* to sink, and was reeled up in 34" 35^ Besides this, 

 the wire can be wound in from depths up to 4,000 fathoms, while the 

 vessel is proceeding at 8 or 9 knots, but with hemp line the vessel must 

 remain stationary. The wire is coiled on a small drum, and passed over 

 a pulley attached to an " accumulator," a series of springs composed of 

 steel or india-rubber, which take off any excessive strain from the line, in 

 case of the vessel pitching heavily.* Wire sounding apparatus is now 

 also manufactured for ordinary ships' use ; when not in frequent use, ti« 

 drums of wire should be kept in a solution of caustic soda, or in oil or 

 lime-water, to prevent oxidation. 



Depth. — For a comprehensive view of this subject, which of course does 

 not affect navigation, however interesting it may be to the physical 

 geographer, we must refer the reader to the illustrative diagram, as a 

 verbal account of the depths obtained in these and other voyages would 

 convey but little intelligible information. These researches are beyond 

 the scope of the ordinary navigator, and are here only cursorily reviewed 

 as matters of interest. The diagram can only be considered as theoretical, 

 the number of soundings hitherto taken being extremely small as com- 

 pared with the vast extent of the Ocean. 



The greatest depth hitherto found in the Atlantic Ocean is 4,561 

 fathoms, or nearly 5^ statute miles ; this depth was found in 1883, by the 

 U.S. steamer Blake, in lat. 19° 41' N., long. 66° 24' W., about 105 miles 

 north-westward of St. Thomas, and near where H.M.S. Challenger found 

 3,875 fathoms, in lat. 19° 41' N., long. 65° 7' W. The U.S.S. Enterprise, 

 in 1886, found 4,529 fathoms, bottom of brown ooze, in lat. 19° 53' N., 

 long. 65° 45' W. In 1889, the U.S.S. Dolphin found 3,441 fathoms, in 

 lat. 30° 49' N., long. 25° 20' W. A depth of 3,428 fathoms was found by 

 the U.S.S. Blake, in the Caribbean Sea, in lat. 19° 1' *N., long. 81° 2' W., 

 north-westward of Jamaica, situated in a deep trough extending from 

 the Windward Passage into Honduras Gulf, and called by the Americans 

 the Bartlett Depression. 



• The Accumulator is generally composed of a number of strong vulcanized india- 

 rubber springs, combined at their extremities ; and its use is two-fold •.—Jirst, to indicate 

 by its elongation any excessive strain upon the sounding or dredging line, which passes 

 through the block ; and second, to ease off the suddenness of such strain, and give time 

 for the action by which it may be relieved. This is specially valuable in deep-sea 

 Bounding and dredging when the vessel is pitching ; for the friction of two or three 

 miles of immersed line is so great as to prevent its yielding to any sudden jerk, such as 

 that given to its attached extremity by a vertical motion of a few feet when the vessel 

 rises to a sea. And it is absolutely needful when dredging is carried on from a large 

 ▼easel ; since, whenever the dredge fouls, the momentum of the vessel, however slowly 

 It might be moving through the water, would cause the line to part, if the strain were 

 sudden instead of gradual. 



N.A.O. 81 



