LEAST SQUARES 



least squares— Any procedure that involves min- 

 imizing the sum of squared differences. For 

 example, the deviation of the mean from the 

 population is less, in the squared sense, than any 

 other linear combination of the population 

 values. (5) 



lee— Shelter, or the part or side sheltered or 

 turned away from the wind or waves. (61) 



lee tide— See leeward tidal current. 



leeward — The direction toward which the wind 

 is blowing; the direction toward which waves 

 are travelling. (61) 



leeward tidal current— A tidal current setting 

 in the same direction as that in which the wind 

 is blowing. (68) 



leeward tide— Obsolete form. See leeward tidal 

 current. 



lenticular— In the shape of a double convex lens. 

 Applied to commonly occurring lens-shaped 

 sediment or rock bodies of all sizes. Also ap- 

 plied to clouds that attain this shape in the proc- 

 ess of dissipation. 



leptocephalus— The small, elongate, transparent, 

 planktonic larva of the eel (AnguiUa). 



lesser ebb— The weaker of two ebb tidal currents 

 occurring during a tidal day, usually associated 

 with tidal currents of mixed characteristics. 

 (66) See mixed current. (See figure for 

 current curve.) 



lesser flood— The weaker of two flood tidal cur- 

 rents occurring during a tidal day, usually asso- 

 ciated with tidal currents of mixed character- 

 istics. (66) See mixed current. {See figure 

 for current curve.) 



levee — An embankment bordering one or both 

 sides of a seachannel or tlie low-gradient sea- 

 ward part of a canyon or valley. 



level ice — Ice with a flat surface, which has never 

 been hummocked; typical with regard to bays, 

 gulfs, straits, archipelagoes, and shallow waters, 

 where the ice formation occurs in undisturbed 

 conditions. (74) 



level of no motion — See layer of no motion. 



level surface — A surface which at every point is 

 perpendicular to the plumb line of the direction 

 in which gravity acts. 



light absorption — See absorption. 



light and dark bottle technique— <S'ee oxygen 

 technique. 



light bottle — A container used for measuring 

 photosynthetic activity of primary producers. 



light floe — In sea ice reporting, an ice floe gen- 

 erally less than 2 feet thick. (59) 

 light ice — Sea ice less than 2 feet thick. (68) 



light ice floe — See light floe, 

 light intensity — See luminous intensity, 

 light minerals — Detrital minerals in rock or sedi- 

 ments that have a specific gravity of less than 

 2.8 and usually are light in color. Examples 

 are quartz, feldspar, calcite. (2) 



lightship — (or light vessel). A distinctively- 

 marked ship, anchored or moored at a charted 

 point, to serve' as an aid to navigation. (66) 



light vessel — See lightship. 



lily-pad ice — Pancake ice when the cakes are not 

 more than about 18 inches in diameter. (68) 



liman — Shallow coastal lagoon or embayment 

 with a muddy bottom; also a region of mud or 

 slime deposited near a stream mouth. (2) 



lima coast — An alluvial coast usually character- 

 ized by many lagoons. 



limestone — A general term for a class of rocks 

 which contain at least 80 percent of the carbo- 

 nates of calcium or magnesium. Varieties of 

 limestone take their names from the source ma- 

 terial, for example, algal limestone, reef lime- 

 stone, coquina, crinoidal limestone, etc. 



limited form wave — Deformation of the wave by 

 the formation of a sharp crest followed by a 

 propagation with bubbling of water on the fi'ont 

 face until the final breaking into a roller. 



limiting ray — The sound ray which becomes tan- 

 gent at the depth where the sound velocity is at 

 maximum. 



limnology — Tlie physics and chemistry of fresh 

 water bodies and of the classification, biology, 

 and ecology of the organisms living in them. 



(5) 

 Limnoria — (or gribble). 1. A genus of crusta- 

 cean borers. 



2. The common name of this group. Mem- 

 bers of this group are the most destructive of 

 the crustacean borers. 



3. See crustacean borer and marine borer, 

 limpet — One of several suborders (Docoglossa, 



Patellacea, Fissurellidae, or Zygobranchia) of 

 flattened cone-shaped gastropods in which the 

 spiral of tlie shell is absent or not apparent. 



linear amplifier — A pulse amplifier in which the 

 output pulse height is proportional to an input 

 pulse height for a given pulse shape up to a point 

 at which the amplifier overloads. (70) 



linear transducer — A transducer for which the 

 pertinent measures of all sound waves concerned 

 are linearly related. (69) 



line hydrophone — A directional hydrophone 

 consisting of a single, straightline element, or 

 any array of contiguous or spaced electroacous- 

 tic transclucing elements, disposed on a straight 

 line, or the acoustic equivalent of such an array. 

 (69) 



line spectrum — A spectrum whose components 

 occur at a number of discrete frequencies. 



liquid — A state of matter in which the molecules 

 are relatively free to change their positions with 

 respect to each other but restricted by cohesive 

 forces so as to maintain a relatively fixed 

 volume. (27) 



liquid limit— <S'ee Atterberg limits. 



lithif action — See lithification. 



96 



