G 



GAIN . The ratio of the output power, voltage, or 

 current to the input power, voltage, or current. 

 (36) 



GALE . Wind of a force exceeding a specified value, 

 usually 30 miles per hour. In the United States, 

 winds of force 7, 8, 9, and 10 on the Beaufort 

 scale (32-63 miles per hour or 28-55 knots) are 

 classed as gales. Wind of force 7 (32-38 miles 

 per hour or 28-33 knots) is classified as a moder- 

 ate gale; wind of force 8 (39-46 miles per hour or 

 34-40 knots) as a fresh gale; wind of force 9 (47- 



54 miles per hour or 41-47 knots) as a strong gale; 

 and wind of force 10 (55-63 miles per hour or 48- 



55 knots) as a whole gale. (17) 



GALOFARO ■ A whirlpool in the Strait of Messina; 

 one time called "Charybdis." (14) 



GALS . Measurements of gravity are expressed in 

 gals (for Galileo) and milligals. One gal is equal 

 to an acceleration of one centimeter per second 

 per second. Values, of gravity on the earth's 

 surface range approximately between 978.0490 gals 

 at the equator to 983.2213 gals at the poles 

 (+ 5200 milligals) . A one foot change in elevation 

 is equivalent to a .094 milligal change in gravity 

 on land or a .068 milligal change under water. (35) 



GALVANIC CELL (ELECTRIC BATTERY) . An electrolytic 

 cell in which a chemical reaction occurs that 

 produces electrical energy. 



GALVANIC CORROSION . The corrosion above normal 

 corrosion of a metal that is associated with the 

 flow of current to a less active metal in the same 

 solution and in contact with the more active metal. 

 (35) 



GALVANIC SERIES . A list of metals and alloys 

 arranged in order of their relative potentials in 

 a given environment. The order of their arrange- 

 ment in this list may be different in other 

 environments . (35) 



GALVANOMETER . An instrument used to measure small 

 amounts of electric current or to detect its 

 presence or direction by means of the deflections 

 of a magnetic needle (or wire coil) placed in a 

 magnetic field. 



GAMETE . A protoplasmic body incapable of giving 

 rise to another individual until after fusion with 

 another gamete. (18) 



GAMETOPHYTE . See ALTERNATION OF GENERATIONS. 



GAMMA . 1. High energy electromagnetic radiation 

 emitted during the fission process, nuclear decay 

 and /or Bremsstrahling. 



2. A gamma is a unit of magnetic force 

 equal to 10"^ oersteds. 



GAP . A steep-sided depression cutting transversly 

 across a RIDGE or RISE. (26) 



GARUA . A thick, damp fog on the coasts of Ecuador, 

 Peru, and Chile. Also called camanchaca. (17) 



GAS BUOY . A buoy having a gas light. (17) 



GAT . A natural or artificial passage or channel 

 extending inland through shoals or steep banks. 

 (17) 



GCT . GREENWICH CIVIL TIME. 



GEBCO . General Bathymetrlc Chart of the Oceans. 



GEE . A VHF (very high frequency) Radio Navigation 

 system transmitting synchronized pulses, similarly 

 to LORAN. The hyperbolic lines of position are 

 determined by the measurement of the differences 

 in the time of arrival of the pulses which is again 

 also similar to Loran. (29) 



GEIR AND DUKKLE RADIOMETER . The response of the 

 Geir and Dunkle Radiometer is independent of the 

 wave length of the incident energy. For this rea- 

 son this instrument has an advantage over a pyr- 

 heliometer in that it can be used to measure long 

 wave radiation as well as solar radiation and can 

 be used both for daytime and nighttime measure- 

 ments. It also can be used as a net exchange radio- 

 meter to measure the net heat transfer through a 

 surface. 



The radiometer is essentially a heat flow 

 meter. It consists of three bakelite -plates 4 1/2 

 inches square and 1/64 inch thick. The thermopile 

 is constructed by winding 40 gauge constant wire 

 onto the center plate at approximately 88 turns per 

 inch. The wire is then silver-coated on one side 

 of the plate, giving in effect a series of ther- 

 mococouple junctions on opposite sides of the 

 plate. 



Aluminum cover plates are mounted on both 

 sides of the thermopile. These plates increase 

 the thermal capacity without appreciably increasing 

 the thermal resistance, therby damping out minor 

 variations in heat flow caused by fluctuations in 

 the air stream. The cover plates also give addi- 

 tional strength and weather resistance. The upper 

 aluminum plate is painted black to absorb the in- 

 cident radiation, and the lower aluminum plate is 

 highly polished to reduce the emissivity and absorb- 

 tivity to the lowest possible values. When the 

 instrument is used as a net exchange radiometer, 

 both the upper and lower aluminum plates are 

 painted black. 



Since long wave radiation will not penetrate 

 glass, no protective coverings are put over the 

 sensitive surfaces. The sensing unit is mounted 

 in the air stream from a small blower to maintain 

 uniform values of the unit thermal resistance from 

 both meter surfaces. The air stream also prevents 

 the deposit of dust or dew on the meter surface. 

 (35) 



GEK . See GEOMAGNETIC ELECTROKINETOGRAPH. 



GEM. Ground Effects Machine. 



GENERATING AREA . In wave forecasting, the con- 

 tinuous area of water surface over which the wind 

 blows in essentially a constant direction. Some- 

 times used synonymously with FETCH LENGTH. (11) 



GENERATION OF WAVES . 1. The creation of waves by 

 natural or mechanical means . 



2. In wave forecasting, the 

 creation and growth of waves caused by a wind blow- 

 ing over a water surface for a certain period of 

 time. The area involved is called the GENERATING 

 AREA or FETCH. (11) 



GEODESY . The science which deals mathematically 

 with the size and shape of the earth, usually 

 after accurate measurements of large areas of the 

 surface of the earth; and with surveys in which the 

 size and shape must be considered. (17) 



50 



