bad working conditions. The sampler consists of 

 a spring-loaded bucket actuated only after the 

 device rests squarely on the bottom. The bucket 

 Is carried on a heavy metal bridle which slides 

 on a guide tube, and two heavy springs on the 

 frame bear on the movable bridle. In the set 

 position the springs are held by two catches which 

 fit Into a pair of holders and these are triggered 

 when the device strikes bottom. On release, the 

 springs bear on the bridle and push the bucket 

 down Into the sediment. At the same time as these 

 are triggered, a release bar moves so that on 

 hoisting the weight goes on the wire and the two 

 halves of the bucket are drawn together taking a 

 sample of the sediment, (35) 



SH . 1. Secretary of the Navy; 

 2. Slgnal-to-Nolse ratio. 



SNAP . Systems for Nuclear Auxiliary Power, developed 

 by AEC. Compact devices to supply power for space, 

 terrestrial and underwater uses. System Is based 

 on conversion of heat to energy. Heat is obtained 

 either from a small nuclear reactor or from the 

 decay of radioisotopes. Characteristics: long 

 life (5-10 years); reliability of power source; 

 independence from environmental conditions; high 

 cost. Power ranges 1-500 milliwatts, 10-200 watts, 

 others in development. (30) 



SNAPPING SHRIMP . Species of shrimp which produce 

 sharp cracking sounds through the rapid closure of 

 the large pincer claw. Greatest populations of 

 snapping shrimp are found in shallow temperate and 

 tropic waters on shell, rock, coral, and sponge 

 bottoms . The noise produced ranges in frequency 

 from 1.5 to 45 kilocycles, and Interferes with 

 sound ranging. (15) 



SNEZHURA . See SLUSH. 



SNORKEL . A tube used by skin divers which permits 

 breathing without raising the nose or mouth out of 

 the water when swimming face down on the surface of 

 the water. One end of the tube is held in the 

 mouth of the swimmer while the other end protrudes 

 above the surface. 



SNOWBLINK. See SKY MAP. 

 SNOW SLUSH . See SLUSH. 



SOFAR . (Sound Fixing and Ranging) 



In most parts of the oceans there exists a 

 natural sound channel, which extends from very 

 near the surface to a depth of approximately 12,000 

 feet. This channel has an acoustical center, or 

 axis, which is generally between 1,500 to 4,000 

 feet below the surface. The sound from a small 

 bomb detonated near this axis can be received by 

 a monitoring station at ranges up to 3,000 miles. 

 The depth of the sound channel axis varies in dif- 

 ferent oceans and latitudes, but for any particu- 

 lar location its depth remains fairly constant. 



The Sofar system consists of several widely 

 separated shore-based listening stations (each 

 connected by electric cable to an underwater HY- 

 DROPHONE at the depth of the sound channel axis 

 for that location) . Sounds from a correctly set 

 distress signal bomb can be heard by several SOFAR 

 stations at very great ranges, if not shadowed by 

 a land mass . 



The listening stations used in SOFAR are 

 precisely synchronized in time by radio. There- 

 fore, since underwater sound radiates in all direc- 

 tions at a nearly uniform rate, it is possible to 

 compute the location of the sound source by com- 

 paring the times when the signal is received at 

 the various listening stations . Thus , when such 

 a signal Is received, the approximate location of 

 the signal source can be determined within a few 

 minutes. (29) 



SOLENOID . A tube formed in space by the Intersec- 

 tion of unit-interval Isotlmlc surfaces of t»«J 

 scalar quantities. The number of solenoids en- 

 closed by a space curve is therefore equal to the 

 flux of the vector product of the two gradients 

 through a surface bounded by the curve, or 



j j (V*l X V*2) • de = ^ *ld*2. 



where ds is the vector element of area of a surface 

 bounded by the given curve. 



Solenoids formed by the Intersection of sur- 

 faces of equal pressure and density are frequently 

 referred to in meteorology. A barotropic atmos- 

 phere implies the absence of solenoids of this 

 type, since surfaces of equal pressure and density 

 coincide. (24) 



SOLION . Solion is a contraction of the phrase, 

 solution of ions. It refers to a class of liquid 

 state electrochemical devices which can be used 

 as signal processing systems and transducers. 



The solion electrochemical system is similar 

 to an electrolysis system. However, the former 

 have the advantage of indefinite life expectancy 

 since the chemicals used are regenerated. 



SOLITARY WAVE . A wave of translation consisting 



of a single crest rising above the undisturbed 



water level without any accompanying trough. The 



rate of advance of a solitary wave depends upon 



the depth of the water and is usually expressed 



by the formula: / ,^ , . . in which r is the 

 r= yg(d + h), 



rate of advance, g the acceleration of gravity, d 

 the depth of water, and h the height of wave, the 

 depth and height being measured from the undis- 

 turbed water level. (14) 



SOLSTITIAL TIDES . Tides occurring near the times 

 of the solstices. The tropic range may be ex- 

 pected to be especially large at these times. (14) 



SOMALI CURRENT , An ocean current flowing south- 

 westward along the coast of Somaliland (East Africa) 

 as a continuation of the NORTH EQUATORIAL CURRENT, 

 In summer (Northern Hemisphere), when the north 

 equatorial current and the EQUATORIAL COUNTERCUR- 

 RENT are replaced by an eastward flowing monsoon 

 current, the Somali current reverses its direction 

 and flows north from about 10°S, (24) 



SONAR , Sonar is the method or equipment for deter- 

 mining, by underwater sound, the presence, location, 

 or nature of objects in the sea. The word "sonar" 

 is an acronym derived from the expression "SOund 

 NAvigation and Ranging." (1) 



SONAR BACKGROUND NOISE . Sonar background noise is 

 the total noise that interferes with the reception 

 of the desired signal. The noise is that presented 

 to the final receiving element, such as a recorder 

 or the ear of a listener. (1) 



SONAR BOOMER TRANSDUCER . This transducer consists 

 of a flat, epoxy-encapsulated coll with a spring- 

 loaded aluminum face plate. When the capacitor 

 bank from which the energy is obtained is dis- 

 charged into the coil of the transducer, eddy cur- 

 rents generated in the aluminum disk create a 

 strong magnetic field that is opposed to that in 

 the coil. Because the opposed magnetic fields 

 cause the aluminum disk to be driven away from the 

 coil with tremendous force, a large pressure wave 

 is generated in the surrounding water. (30) 



SONAR DOME INSERTION LOSS . The sonar dome inser- 

 tion loss caused by the addition of a sonar dome is 

 the increase in transmission loss between the elec- 

 trical terminals of a specified transducer and an 

 external field point at which transmission or recep- 

 tion of sound occurs . (1) 



SONAR DOME LOSS PATTERN . The sonar dome loss pat- 



109 



