response of a sonar transducer as a function of 

 frequency for some specified bearing may be de- 

 scribed as a spectrum pattern. (4) 



SPEED OF SOUND IN SEA WATER . Three variables 

 govern the speed (S) of sound In a fluid. They 

 are density (P), compressibility (^) , and the 

 ratio between the specific heats of the fluid at 

 constant pressure and at constant volume (y). 

 The following formula Is applicable: 



For atmospheric pressure 29.92 Inches of mer- 

 cury, temperature 60 degrees F, and salinity 34.85 

 parts per thousand, the density of sea water Is 64 

 pounds per cubic foot and the compressibility ap- 

 proximately 0.0000435 per atmosphere. Using these 

 values and 32.174 feet per second (the acceleration 

 of gravity at latitude 45 degrees) and 144 square 

 Inches per square foot, and taking v equal to 

 unity, the speed of sound in sea water is computed 

 to be 4945 ft/sec. 



An increase in temperature decreases both den- 

 sity and compressibility, resulting in an Increase 

 in the speed of sound. In sea water, an increase 

 in pressure or salinity produces a slight Increase 

 in density and a larger decrease in compressibility, 

 resulting in a net increase in the speed of sound. 

 Thus, in sea water, an increase in temperature, 

 pressure, or salinity results in greater speed of 

 sound. Of the three, temperature has the greatest 

 Influence on the speed of sound in sea water. The 

 pressure affect is slight, and the change of 

 salinity is pot sufficiently great to exercise a 

 marked influence on the speed. (12) 



SPHERICAL BUOY . A buoy, the above-water part of 

 which, is hemispherical in shape, (17) 



SPHERICAL WAVE . A spherical wave is a wave in which 

 the wave fronts are concentric spheres . (9) 



SPICULE . The tissue of various Invertebrates, 

 such as some of the sponges, radiolarlans, holo- 

 thurians , etc., are supported by minute chrystal- 

 like spicules consisting of either silica or cal- 

 cium carbonate. Varying complexity in construc- 

 tion leads to spicules being classified as: (1) 

 Monaxons - having a single axis, (2) Trlaxons - 

 having three axes crossing at right angles, (3) 

 Tetraxons - having four axes not in the same plane, 

 which diverge from a common point, (4) Polyaxons 

 - having several equal rays diverging from a point, 

 and (5) Desmas - characterized by seeming lawless- 

 ness of structural plan since divergent main mem- 

 bers commonly bear spiny or' warty excrescences 

 growing in all directions. 



Spicules contribute to the fossile record and 

 to marine sediments since the siliceous ones in 

 particular are preserved upon decomposition of the 

 animals soft parts. (21,19) 



SPILHAUS -MILLER SEA SAMPLER . An Instrument re- 

 sembling the BATHyTHERMDGRAPH and operating In a 

 similar fashion, with the additional ability of 

 obtaining water samples at discrete depths within 

 the limit of operation. Basically a bathythermo- 

 graph to which 12 small sea water sampling bottles 

 are attached. It performs the same functions as a 

 cast of Nansen bottles and REVERSING THERMOMETERS 

 to limited depths, but with less accuracy. It Is 

 useful for studies of shallow water areas, bays, 

 and estuaries, where rapidity of sampling is of 

 greater importance than the degree of accuracy of 

 temperatures . 



The sea sampler Is operated in much the same 

 manner as the bathythermograph, and is lowered 

 from a bathythermograph winch. The temperature is 

 recorded both during lowering and hoisting on a 

 smoked-glass slide. The water sampling bottles 

 have valves at each end and are sent down open. 

 They are closed at predetermined depths while the 

 sampler is rising to the surface. (35) 



SPIN ECHO STORAGE . The utilization of electron 

 spin resonance to store data processing information 

 for very-high-speed access. 



SPIT . A low tongue of land, or a relatively long, 

 narrow shoal extending from the shore. (17) 



SPITSBERGEN CURRENT . An ocean current flowing 

 northward and westward from a point south of 

 Spitsbergen, and gradually merging with the EAST 

 GREENLAND. CURRENT in the Greenland Sea. The 

 Spitsbergen current is the continuation of the 

 northwestern branch of the NORWEGIAN CURRENT. (17) 



SPIASHNDC . A Navy buoy for measuring waves by 

 telemetering vertical motions of the buoy to a 

 ship via an FM radio transmitter. See TELEMETER- 

 ING WAVE BUOY. 



SPLIT TRANSDUCER . A split transducer is a direc- 

 tional transducer in which electroacoustlc trans- 

 ducing elements are so divided and arranged that 

 each division is electrically separated. (1) 



SPOIL GROUND BUOY . A buoy marking the discharge 

 area for dredged material. The expression is not 

 generally used in United States waters. (17) 



SPONGES . Sessile invertebrates which inhabit 

 fresh, brackish, or salt water and occur from 

 tropic to polar areas . They attach to submerged 

 objects and, in warm waters, afford shelter for 

 great concentrations of snapping shrimp. Sponges 

 vary in size from very minute to several feet In 

 diameter. (15) 



SPONGIN . Some of the sponges (Class Demospongiae) 

 secrete a skeletal material called spongln, which 

 is a sulphur-containing protein (seleroprotein) 

 that is insoluble, inert chemically, and resistant 

 to protein-digesting enzymes. Commonly known as 

 the "bath sponge". (19) 



SPONTANEOUS PNEUMOTHORAX . This disease or acci- 

 dent refers to the forceful entry of air into the 

 chest cavity. It results from an over expansion 

 of air in the lungs . 



SPORANGIUM . A SPORE case within which spores are 

 formed. (18) 



SPORE . A minute reproductive body produced by 

 plants. Usually unicellular, but sometimes multi- 

 cellular. The spore is not a reproductive body in 

 bacteria. (18) 



SPOROPHYTE . See ALTERNATION OF GENERATIONS. 



SPREADING . The reduction in acoustic intensity due 

 to an increase in the area over which a given acous- 

 tic energy is distributed is said to result from 

 spreading. (4) 



SPREADING ANOMALY . That part of the propagation 

 anomaly which may be identified with the geometry 

 of the ray paths . (4) 



SPRING RANGE (Sp) . The mean semidiurnal range of 

 tide when spring tides are occurring; the mean 

 difference in height between spring high water and 

 spring low water. (17) 



SPRING TIDES OR TIDAL CURRENTS . Tides of Increased 

 range or tidal currents of increased velocity oc- 

 curring semimonthly as the result of the moon being 

 new or full. The spring range of tide is the aver- 

 age semidiurnal range occurring at the time of 

 spring tides and is most conveniently computed from 

 the harmonic constants . It is larger than the mean 

 range where the type of tide is either semidiurnal 

 or mixed, and is of no practical significance where 

 the type of tide is diurnal. The average height of 



102 



