sabellid — See tubeworm. 



sac — 1. An indentation in the contours on a chart 

 showing submarine relief whicli is analogous to 

 a gulf on the surface. The opposite term is 

 submarine peninsula. 



2. In biology, a sack, bag, or pouch. 



saddle — A low part on a ridge or between 

 seamounts. (62) 



sailing directions — Information published in 

 book form describing coasts, waters, channels, 

 harbor facilities, etc., for use of mariners. (30) 



sailing ice — See scattered ice. 



sailor's purse — (or mermaid^s purse, skate 

 bar7'ow). The tough egg capsule of skates and 

 certain rays, usually deposited on mud and sand 

 flats. The capsules are oblong with a horn ex- 

 tending lengthwise from each of the four cor- 

 ners and are blackish when seen on the beach. 



St. Elmo's fire — (also called Ehno^s fire, corpo- 

 sant) . A corona discharge. 



salgaso — See aguaje. 



salient point — A point formed by a conspicuous 

 projection extending outward from the general 

 trend of the coast. 



salina — A salt marsh or salt pond separated 

 from the sea but flooded by high tides. Shallow 

 salt ponds are used to evaporate the water in 

 the commercial production of salt and are called 

 salt gardens or salterns. 



salinity — A measure of the quantity of dissolved 

 salts in sea water. It is formally defined as the 

 total amount of dissolved solids in sea water in 

 parts per thousand (°/oo) by weight when all 

 the carbonate has been con\ei'ted to oxide, the 

 bromide and iodide to chloride, and all organic 

 matter is completely oxidized. These qualifica- 

 tions result from the chemical difficulty in dry- 

 ing the salts in sea water. In practice, salinity 

 is not determined directly but is computed from 

 chlorinity, electrical conductivity, refractive 

 index, or some other property whose relation- 

 ship to salinity is well established. 



Because of the Law of Constancy of Propor- 

 tions, the amount of chlorinity in a sea water 

 sample is used to establish the sample's salinity. 

 The relationship between chlorinity CI and 

 salinity S as set forth in Knudsen's Tables is : 



S=0.03+1.805 CI. 



A joint committee of lAPO, UNESCO, 

 ICES, and SCOR proposed the universal adop- 

 tion of the following equation for determining 



salinity from chlorinity: S= 1.80655 CI. It 

 was adopted by lAPO in 1963 and ICES in 

 1964. 



salinity bridge — See salinometer. 



salinometer — (or salinity bridge). Any device 

 or instrument for determining salinity, espe- 

 cially one based on electrical conductivity 

 methods. (5) 



salp — Any one of a class (Thaliacea) of marine 

 animals which are transparent pelagic repre- 

 sentatives of the tunicates. The body is more 

 or less cylindrical and possesses conspicuous 

 ring-like muscle bands, the contraction of which 

 propels the animal through the water. Several 

 kinds are bioluminescent. 



salt — Any substance which yields ions, other than 

 hydrogen or hydroxyl ions. A salt is obtained 

 by displacing the hydrogen of an acid by a 

 metal. (27) 



saltation — That method of sand movement in a 

 fluid in which individual particles leave the bed 

 by bounding nearly vertically and, because the 

 motion of the fluid is not strong or turbulent 

 enough to retain them in suspension, return to 

 the bed at some distance downstream. (61) 



salt crust — Salt that is forced out of young sea ice 

 by crystal growth, pushed upward, and deposited 

 on the surface of the ice. (A salt crust surface 

 is wet even at low temperatures.) (59) 



salterns — See salina. 



salt flower — See ice flower. 



salt gardens — See salina. 



salt marsh — Flat, poorly drained coastal swamps 

 which are flooded by most high tides. 



salt pans — Shallow pools of brackish water used 

 for the natural evajwration of sea water to obtain 

 salt. (2, 30) 



salt water — See sea water. 



salt water wedge — An intrusion in a tidal estu- 

 ary of sea water in the form of a wedge charac- 

 terized by a pronounced increase in salinity from 

 surface to bottom. 



sand — Loose material which consists of grains 

 ranging between 0.0625 and 2.0000 millimeters 

 in diameter. See phi grade scale. 



sand apron — Sand deposited along the shore of a 

 reef lagoon. (2) 



sand bar — 1. See bar. 



2. In a river, a ridge of sand built up to or 

 near the surface by river currents. (61) 



sand dollar — See sea urchin. 



207-109 0—66 



139 



