FLUOROMETER . The Fluororaeter is an optical in- 

 strument which will determine the movements of a 

 body of water by responding to the light emitted 

 by a fluorescent dye previously injected in the 

 body of water under consideration. (30) 



FLUX-GATE MAGNETOMETER (SATURABLE REACT OR). The 

 essential element of this instrument, which is 

 used for detailed studies of the earth's magnetic 

 field on a local basis, is the flux-gate. This 

 consists of two identical saturable cores of high 

 permeability, oppositely wound with identical coils. 

 An alternating current In these coils magnetizes 

 them first with one polarity, then in the opposite 

 sense. If an additional field is present, such as 

 the earth's field, it will add to the flux in one 

 coil while decreasing that in the other. As a 

 result, the voltage drop across the two coils will 

 differ. The amount of this difference is propor- 

 tional to the unvarying field , which can thus be 

 measured by noting the average voltage difference 

 between the two halves of the flux gate. This can 

 be done to an accuracy of about —1 gamma. In use, 

 a part of the earth's field is balanced out by an 

 additional winding surrounding both cores and 

 carrying direct current. 



In airborne use, the recording flux gate is 

 kept aligned with the magnetic field by the use of 

 two additional flux gates. When these are at right 

 angles to the earth's field, they generate no vol- 

 tage, but if they depart from this position, they 

 can be made to generate voltages which operate 

 motors returning them to proper alignment . In this 

 fashion the recording element is held always paral- 

 lel to the total field. (35) 



FLYBACK . The recycling period of the sawtooth- 

 modulated FM oscillator. (5) 



FMO . Frequency modulated oscillator. (5) 



FOAM LINE . The front of a wave as it advances 

 shoreward, after it has broken. (11) 



FOG. A visible assemblage of numerous tiny drop- 

 lets of water, or ice crystals formed by condensa- 

 tion of water vapor in the air, with the base at 

 the surface of the earth. If this is primarily 

 the result of movement of air over a surface of 

 different temperature, it is called advection fog; 

 if primarily the result of cooling of the surface 

 of the earth and the adjacent layer of atmosphere 

 by radiation, it is called radiation fog. Cali- 

 fornia fog is fog peculiar to the coast of Cali- 

 fornia and its coastal valleys. Monsoon fog is an 

 advection fog occurring along a coast where monsoon 

 winds are blowing, when the air has a high specific 

 humidity and there is a large difference in the 

 temperature of adjacent land and sea. Shallow and 

 often dense radiation fog, through which the sky 

 is visible, is called ground fog. Thin fog of 

 relatively large particles, or very fine rain 

 lighter than drizzle is called mist. Fog formed 

 at sea, usually when air from a warm-water surface 

 moves to a cold-water surface, is called sea fog. 

 Fog produced by apparent steaming of a relatively 

 warm sea in the presence of very cold air is called 

 frost smoke, sea smoke, arctic sea smoke, water 

 smoke, barber, or steam fog. Fog consisting of 

 ice crystals is called ice fog. Frozen fog is 

 called pogonip. A simulation of true fog by at- 

 mospheric refraction is called mock fog. Haze 

 due to the presence of dust or smoke particles in 

 the air is called dry fog. A mixture of smoke and 

 fog is called smog. (17) 



FOG BUOY . Position buoy. (17) 



FOLD . A bend in a layer or layers of rock strata. 

 (27) 



FOLLOWING SEA. See BEAM SEA. 



FOLLOWING WIND . In wave forecasting, wind blowing 

 in the same direction that waves are travelling. 

 (11) 



F ORAMIN IF ERA . Minute one-celled marine organisms 

 which secrete a calcareous test (shell), or the 

 test of such an organism. Foraminifera may be an 

 important constituent of some deep sea deposits. 

 If the foraminifera constitute 30 per cent or more 

 of the samples, the sediment is referred to as 

 foraminferal ooze. On the basis of size, foramini- 

 feral ooze usually is classified as mud-sand on 

 bottom sediment charts. (16) 



FORCED WAVE . A wave that is maintained by a 

 periodic force, and the period of a forced wave 

 must always coincide with the period of the force, 

 regardless of the dimensions of the basin or of 

 frictional influence. 



Floating Ocean Research and Development 



FORDS 

 Station. 



FOREDEEP . A deep, elongated oceanic depression 

 fronting a mountainous land area. It is a trench 

 if it has steep sides and a trough if it has gently 

 sloping sides. (17) 



FOREL SCALE . A 

 color. The Fore 

 sists of a serie 

 ammonical copper 

 chroraate in such 

 graduation of co 

 These vials are 

 compared directl 



basic means of determining water 

 1 scale used on Navy surveys con- 

 s of 11 small vials containing 

 sulphate and neutral potassium 

 proportions that a different 

 lor is imparted to each vial, 

 numerically designated and are 

 y with sea water samples. (29) 



FORESHORE . The part of the shore, lying between 

 the crest of the seaward berm (or the upper limit 

 of wave wash at high tide) and the ordinary low 

 water mark, that is ordinarily traversed by the 

 uprush and backrush of the waves as the tides rise 

 and fall. (11) 



FORMATION . A stratum or a set of strata possessing 

 a common suite of lithological and/or faunal charac- 

 teristics. (27) 



FOULING . The assemblage of marine organisms that 

 attach to and grow upon underwater objects. (15) 



FOULING PLATES . These are metal plates submerged 

 to allow attachment of the fouling organisms and 

 are analyzed on a monthly or seasonal schedule. 

 Determination of species, growth rate, and growth 

 pattern, as influenced by environmental conditions 

 and time, are the aims of these programs. (35) 



FOXBORO TIDE GAGE . This instrument is operated by 

 the change of pressure caused by the change in 

 water level above a pressure plate. The pressure 

 change is converted to a pen deflection in a re- 

 corder, and the change in the level of the tide 

 appears as a graph. The advantages of this gauge 

 are its ease of installation and its capacity for 

 transmitting measurements to one or more receivers 

 as far as 500 feet from the sensing element. It 

 can be used at any place where sufficient water is 

 present to cover the element. No permanent instal- 

 lation of any type is required. It would appear' 

 that this type of instrument would prove useful 

 in areas that do not readily permit the use of the 

 standard automatic portable tide gage and/or in 

 instances where data are to be collected for brief 

 periods of time. It is also possible that the 

 recording method may facilitate the data handling. 

 (35) 



FRACTURE ZONE . A zone of unusually irregular 

 topography of the sea floor averaging 50 nautical 

 miles in width and normally greater than 1000 

 nautical miles in length. This zone is character- 

 ized by large SEAMOUNTS, steep-sided or nonsym- 

 metrical RIDGES, TROUGHS or ESCARPMENTS. (26) 



U8 



