[73] FISHERIES OF THE UNITED STATES. 585 



its use. A curve of this kind is easily made, and once obtained no fur- 

 ther measurements of wire are needed so long as the same kind of reel 

 and wire are continued in use. The loss of wire from the reel, or the 

 addition of wire thereto, does not require a new curve if the curve be 

 made long enough in the first instance. It is believed that it is now in 

 use wherever known. For a full description, see Sigsbee's Deep-Sea 

 Sounding and Dredging, page 37 and Plate 41. 



The necessity for its use appears from the following : Eeels for deep- 

 sea sounding are made of such a size that their drums will exactly ac- 

 commodate one fathom of the sounding wire at a single turn (although 

 this is not essential). While each turn of the first layer wound about 

 one of them is, therefore, one fathom in length, those that are above the 

 first layer measure more, according to their distance from the drum. 

 Each reel is rigidly attached to an axle, on which is a worm to conuect 

 with the train of a register for recording the number of revolutions of 

 the reel. It is evident that the readings of the register show the num- 

 ber of turns of wire paid out or reeled in, but not the number of fath- 

 oms ; and since the turns are almost constantly varying in length, it 

 becomes necessary to have some ready means of reducing them to fath- 

 oms, in order to arrive at the depth of the sounding. 



With a correction curve at hand, the number of turns of wire in use 

 upon the reel and the number of turns paid out at any sounding are re- 

 ferred to the curve, whence the corresponding fathoms are found in a 

 few seconds. Plate 41 of Deep-Sea Sounding and Dredging explains 

 the construction and the method of reading the curve. 



Steel Piano-forte Wire, for deep-sea sounding. 



United States Fish Commission. 



" The wire used by the American expeditions for sounding purposes 

 is steel piano-forte wire, of No. 22 Birmingham (Stubb's) gauge, or 

 about No. 21 American wire gauge, and measures 0.028 of an inch in 

 diameter. It weighs 14^ pounds to the nautical mile (1,000 fathoms 

 approximately) in air, and consequently about 12 pounds in water. The 

 English-made wire has a tensile strength of from 200 to 240 pounds, is 

 provided in lengths of 100 to 400 fathoms, and is made up in 18-inch 

 coils, weighing about 60 pounds, and wrapped with oiled paper. The 

 American wire, called music wire No. 13, has a tensile strength some- 

 what less than that of the English wire, and seems to have a higher 

 polish. It is made up in 9 or 10-inch coils, stowed neatly within sealed 

 tin cases, which protect it better than the English wrapping." Great 

 care is required in the preservation of the wire to prevent corrosion. 

 When not in use the sounding reel with its wire is kept in a tank of 

 sperm or lard oil, free from acid impurities. One of the greatest diffi- 

 culties originally encountered in the use of considerable lengths oi 

 sounding wire was the construction of suitable splices, which should be 



