structed in any test during uhlch frequent or con- 

 tinuous measurements of both stress and strain are 

 made. It is consnonly constructed for the Compres- 

 sion, Tension and Torsion Tests, It is usually 

 necessary for the detexmlnatlon of Deformation 

 Energy, Elastic Limit, Modulus of Elasticity, 

 Modulus of Rigidity, Proportional Limit and Yield 

 Strength. It is often useful in determination of 

 Elongation, Modulus of Rupture, Ultimate Strength 

 and other related properties. 



STRONG GALE . See GALE. 



SUB-BOTTOM DEPTH RECORDER . The SDR is a compact 

 seismic equipment which is capable of providing con- 

 tinuous soundings of sub-bottom strata. The sound 

 energy source is an electrical spark discharge in 

 water. An intense spark discharge, confined to a 

 very small volume of water, will vaporize the water 

 and produce high-pressure bubbles whose expansion 

 and contraction radiate acoustic energy. The SDR 

 utilizes the low frequency energy output of the 

 spark discharge source to obtain continuous records 

 of bedrock lying below more than 450 feet of sedi- 

 ment. The transmitter section works in conjunction 

 with a recorder and float assembly which is towed 

 astern by means of the hydrophone and electrode 

 cables. The hydrophone which detects the Incoming 

 signal is housed within the float structure. (30) 



SUBCUTANEOUS EMPHYSEMA . See EMPHYSEMA. 



SUBHARMONIC . A subharmonic is a sinusoidal quan- 

 tity having a frequency that is an Integral submul- 

 tiple of the fundamental frequency of a periodic 

 quantity to which it is related . (2) 



SUBMARINE CANYON . See CANYON. 



SUBMARINE FREE COMMUNICATION EFFECT . Free communi- 

 cation effect is the effect caused by a partly 

 filled tank that is open to the sea as in the case 

 of a ballast tank with open vents. In this case 

 not only does the water in the tank shift with roll 

 or pitch, but water may actually enter or leave the 

 tank through the opening to sea causing a change 

 in weight and therefore a shift in the center of 

 gravity. (33) 



SUBMARINE FREE SURFACE EFFECT . Free surface effect 

 is that effect caused by free surface of a liquid 

 in a partly filled tank which reduces stability 

 because the liquid Is free to shift within the tank 

 boundaries in the direction of the roll or pitch of 

 the vessel. (33) 



SUBMARINE ISTHMUS . A submarine elevation joining 

 two land areas and separating two basins or depres- 

 sions by a depth less than that of the basins. (17) 



SUBMARINE PENINSULA . An elevated portion of the 

 submarine relief resembling a peninsula. The op- 

 posite is SAC. (17) 



SUBMARINE PIT . A cavity on the bottom of the sea. 

 Also called submarine well. (17) 



SUBMARINE SPRING . A spring of water issuing from 

 the bottom of the sea. (17) 



SUBMARINE WAVE RECORDER . A wave recorder which 

 uses the submarine as a hovering, submerged, stable 

 platform from which to measure oceanographlc vari- 

 ables. In this method essentially an Inverted echo 

 sounder mounted on the deck of a hovering submerged 

 submarine is used plus the travel time required for 

 the vertical sound beam to go from the submarine to 

 the height of the water above the submarine. Thus, 

 changes in water height above the submarine are 

 recorded as changing wave height. (35) 



SUBTROPICAL ANTICYCLONE . See SUBTROPICAL HIGH. 



SUBTROPICAL HIGH (SUBTROPICAL ANTICYCLONE. OCEANIC 

 ANTICYCLONE. OCEANIC HIGH) . One of the semi-per- 

 manent highs of the SUBTROPICAL HIGH-PRESSURE BELT. 

 They appear as centers of action on mean charts of 

 surface pressure. They lie over oceans, and are 

 best developed in the summer seasons. (14) 



SUBTROPICAL HIGH- PRESSURE BELT (SUBTROPICAL RIDGE) . 

 One of the two belts of high atmospheric pressure 

 that are centered, in the mean, near 30°N and 30°S 

 latitudes. These belts are formed by SUBTROPICAL 

 HIGHS. (14) 



SUBTROPICAL RIDGE . 

 BELT. 



See SUBTROPICAL HIGH-PRESSURE 



SUESTADO . A storm with southeast gales, caused 

 by Intense cyclonic activity off the coasts of 

 Argentina and Uruguay, which affects the southern 

 part of the coast of Brazil in the winter. (17) 



SUGAR ICEBERG . An ICEBERG composed of the most 

 porous type of GLACIER ICE. Such ice is formed at 

 very low temperatures, is loosely constructed, and 

 falls apart easily. (25) 



SUGG . To roll with the action of the sea when 

 aground. (17) 



SULPHUR-BOTTOM . A descriptive term frequently ap- 

 plied to the blue whale, and arising from the fact 

 that after feeding for some time in antarctic waters 

 the under portion of their bodies may become in- 

 crusted with yellow diatoms (Cocconeis citicola) . 

 (13) 



SUMATRA . A squall with violent thunder, lightning, 

 and rain, which blows at night in the Malacca 

 Straits, especially during the southwest monsoon. 

 It is intensified by strong mountain breezes. (17) 



SUPERHEAT . Sensible heat in a gas above the amount 

 needed to keep it a gas. (33) 



SUPERSONIC FREQUENCY . See ULTRASONIC FREQUENCY. 



SUBMARINE PHOTOMETER . A device which detects and 

 records directly, in foot-candles, the light exist- 

 ing at the surface of the ocean and all depths down 

 to approximately 150 meters. Through the use of 

 filters, observations are made in the infrared ul- 

 tra-violet ranges of the spectrum. The instrument 

 consists of two 2-pen Brown potentiometer recorders 

 and a detecting unit of 3 photoelectric cells and 

 a Statham STRAIN GAGE. 



In connection with studies of PHYTOPLANKTON , 

 biological oceanographers are generally interested 

 in light penetration. The submarine photometer 

 used in these studies is a WESTON PHOTOELECTRIC 

 CELL enclosed in a watertight housing which is 

 lowered on a two-conductor cable. The amount of 

 light detected by the weston cell is read on a 

 microammeter. (35) 



SURF . The wave activity in the area between the 

 shore line and the outermost limit of breakers . 

 (11) 



SURFACE REVERBERATION . See REVERBERATION. 



SURFACE THERMOMETER . In oceanography, a thermometer 

 used in a bucket of sea water to measure sea surface 

 temperature. (24) 



SURF BEAT . Irregular oscillations of the nearshore 

 water level, with periods of the order of several 

 minutes. (11) 



SURGE . (1) The name applied to wave motion with a 

 period intermediate between that of the ordinary 

 wind wave and that of the tide, say from 1/2 to 



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