LEAD SMOKE 



land ice — See glacier, glacier ice. 



landlocked — A body of water enclosed or nearly 

 enclosed by land, thus protected from the sea. 

 San Francisco Bay is a classic example. 



land sky — The relatively dark appearance of the 

 imderside of a cloud layer when it is over land 

 that is not snow covered. This term is used 

 largely in polar regions with reference to the 

 sky map ; land sky is brighter tlian water sky, 

 but is much darker than ice blink or snow 

 blink. (5) 



lane — 1. See lead. 



2. A narrow, not necessarily navigable, crack 

 in pack ice. It may widen into a lead. (5) 

 Obsolete. 



3. An electronically defined area and system 

 of measurement used in certain electronic con- 

 trolled systems, such as Decca survey and 

 LORAC. A proportional reading of the dis- 

 tance between the two rates which define a lane 

 are taken and define a line of position. 



langley — A unit of energy per unit area commonly 

 employed in radiation theory ; equal to one gram 

 calorie per square centimeter. ( 5 ) 



lanternfish — See myctophid. 



lanthanides — The rare-earth elements from 

 atomic numbers 58 to 71 inclusive. They have 

 chemical properties similar to lanthanum. (41) 



lapilli — Volcanic ejecta ranging from 4 to 32 

 millimeters in diameter. (2) 



lappered ice — See anchor ice. 



lard ice — Rare. See grease ice. 



large calorie — (abbreviated Cal). See calorie. 



large field of ice — See large ice field. 



large ice field — '(or large -field of ice). 1. An ice 

 field over 20 kilometers (10.8 n. miles) across. 

 (74) 



2. A Russian term for an ice field of 2 tx) 10 

 kilometers (1.1 to 5.4 n. miles) in width. All 

 large ice fields would fall into the current WTMO 

 definition of big ice floe. 



large ice skylight — See ice skylight. 



large scale — See scale. 



larva — An embryo which becomes self-sustaining 

 and independent before it has assumed the char- 

 acteristic features of itjs parents. (26) 



last ice — The last appearance of ice in the waters 

 of a particular location, whether it melts locally 

 or is carried off by winds or currents. 



latent heat — The heat released or absorbed per 

 unit mass by a system in a reversible, isobaric- 

 isothermal change of phase. At 0°C, the latent 

 heats of vaporization (or condensation), fusion, 

 and sublimation of water substance are, re- 

 spectively, 

 it,= 597.3 cal/gm 

 Lf = 79.7 cal/gm 

 Zs= 677.0 cal/gm 



latent heat of evaporation — That amount of heat 

 required to change one gram of water into water 

 vapor withoiit a change in temperature. For 



example, 536 calories are required to change one 

 gram of water to water vapor at 100°C at .stand- 

 ard atmospheric pressure. 



lateral line — A system of sense organs possessed 

 by fishes, usually arranged in a single series 

 along the side of the body, and functioning in 

 part to detect low frequency vibrations such as 

 those produced by local disturbances in the 

 water. 



lateral shift — The offset of the position of the 

 peak of an anomaly with the mass of magnetiza- 

 tion (or gravitation). 



latitude correction — The amount of the adjust- 

 ment of observed gravity values to an arbitrar- 

 ily chosen base latitude. 



lava — Molten rock which issues from a volcano or 

 a fissure in the earth's surface and solidifies upon 

 cooling. (See figure for compound volcano.) 



lava delta — A delta like body of lava formed 

 where a lava flow enters the sea. A coast con- 

 sisting of such deltas formed by recent lava flows 

 has a convex shoreline and is called a lava-flow 

 coast. 



lava-flow coast — See lava delta. 



Law of Constancy of Relative Proportions — 

 Regardless of the absolute concentration of total 

 dissolved solids in sea water, the ratios between 

 the more abundant substances are virtually con- 

 stant in the world's oceans. 



Law of Universal Gravitation — Newton's law of 

 gravitation. Gravitation is directly propor- 

 tional to tlie product of the masses of the two 

 bodies and inversely proportional to the square 

 of the distance between them. (37) 



layer — See stratum. 



layer depth — (or isothermal layer depth, mixed 

 layer depth). In oceanography, the thickness 

 of the mixed layer ; or the depth to the top of 

 the thermocline. (5) 



layer depth effect — The weakening of the sound 

 beam owing to abnormal spreading as it passes 

 from an isothermal or a positive gradient layer 

 to an underlying negative layer. 



layer of no motion — A layer, assumed to be at 

 rest, at some depth in the ocean. Tliis implies 

 that the isobaric surfaces within the layer are 

 level, and hence they may be used as reference 

 surfaces for the computation of aibsolute gradi- 

 ent currents. 



This same concept can define a level of no mo- 

 tion or a surface of no motion. (5) 



lead — (or channel, lane). A navigable passage 

 through pack ice. (74) 



A lead may be covered by young ice. From 

 the point of view of the submariner it becomes 

 an ice skylight. 



lead line — (or sounding line). A line, wire, or 

 cord used in sounding. It is weighted at one 

 end with a plummet (sounding lead). (61) 



lead smoke — See frost smoke. 



95 



