penetrates into the interior of the land. In 

 general, the entrance is wider than the length. 

 (17) 



GULF ICE . WINTER ICE formed in a GULF or BAY. 

 (25) 



GULF STREAM . In the Western Atlantic much of the 

 waters of the North and South Equatorial Current 

 combine and flow northward through various passages 

 between the Windward Islands and into the Carrib- 

 bean Sea. Upon reaching the Yucatan peninsula some 

 of the water curves toward the right, flowing some 

 distance off the shore of the Gulf of Mexico, and 

 part of it curves more sharply toward the east and 

 flows directly toward the north coast of Cuba. 

 These two parts reunite in the Straits of Florida 

 to form the Gulf Stream. Off the southeast coast 

 of Florida this current is augmented by a current 

 flowing along the northern coasts of Puerto Rico, 

 Hispaniola, and Cuba. Another current flowing 

 eastward of the Bahamas joins the stream north of 

 these islands. 



The Gulf Stream follows generally along the 

 east coast of North America, flowing around Florida, 

 northward and then northeastward towards Cape 

 Hatteras, and then curving toward the east and 

 becoming broader and slower. After passing the 

 Grand Banks , it turns more toward the north and 

 becomes a broad drift current flowing across the 

 North Atlantic. In a stricter sense that segment 

 of the current popularly called the "Gulf Stream" 

 which lies between the Straits of Florida and Cape 



Hatteras is called the FLORIDA CURRENT. That seg- 

 ment lying between the continental slope off Cape 

 Hatteras and the region to the east of the Grand 

 Banks (about long. 45°W) is called the Gulf Stream. 

 All the easterly and northerly currents of the North 

 Atlantic from the region to the east of the Grand 

 Banks where the Gulf Stream divides are usually 

 placed under the general term NORTH ATLANTIC CUR- 

 RENT. (12-13) 



GULF STREAM SYSTEM . The FLORIDA CURRENT, GULF 

 STREAM and NORTH ATLANTIC CURRENT, collectively. 

 (12) 



GULLY-SQUALL . A nautical term for a violent squall 

 of wind from mountain ravines on the Pacific side 

 of Central America. (12) 



GUT . (1) A narrow passage such as a strait or 

 inlet. (2) A channel in otherwise shallower water, 

 generally formed by water in motion. (11) 



GUYOT . A flat-topped submarine mountain, rising 

 at least 1 killometer above the surrounding ocean 

 floor. (27) 



GUY ROPE . See WIRE ROPE. 



GYROCOMPASS . A compass that is actuated by a 

 rapidly spinning rotor which tends to place its 

 axis of rotation parallel to the earth's axis of 

 rotation. It indicates direction relative to the 

 true north. (14) 



H 



HAAR . A name applied to a wet sea fog or very fine 

 drizzle which drifts in from the sea in coastal 

 districts of eastern Scotland and northeast 

 England. It occurs most frequently in summer. (12) 



HALF LIFE . Each radioactive material has an in- 

 herent characteristic that during a certain deter- 

 minable time one-half of the atoms of that sub- 

 stance will have decayed or lost their original 

 radiation; during the next period of time identi- 

 cal in length with the first period, one-half of 

 the remaining atoms will have also decayed. The 

 half-life period varies in radioisotopes from less 

 than a second to many billions of years. (39) 



HALF -TIDE LEVEL (MEAN TIDE LEVEL) . A plane midway 

 between mean high water and mean low water. (14) 



HAND LEAD . A light sounding lead (7 to 14 pounds), 

 usually having a line of not more than 25 fathoms. 

 (17) 



HAPLOID . The reduced, or n, chromosome number, 

 characteristic of the gametophyte generation. 

 (18) 



HARBOR (British - HARBOUR) . A protected part of 

 a sea, lake, or other body of water used by vessels 

 as a place of safety and/or the transfer of passen- 

 gers and cargo between water and land carriers . 

 (11) 



HARBOUR . See HARBOR. 



HARDY CONTINUOUS PLANKTON RECORDER . This device 

 can be towed for long distances behind any ship at 

 speeds up to 15 knots . It is fitted with fixed 



planes which enable it to be towed at constant 

 depths which aire determined by the amount of towing 

 cable payed out. Water enters 'a small hole in the 

 front and passes through a tunnel and out the back. 

 The plankton are sieved out by a continuously mov- 

 ing band of silk gauze which is slowly wound across 

 the tunnel and into a storage tank of formalin by 

 a system of rollers geared to a propeller on the 

 outside of the instrument. The propeller is turned 

 as it moves through the water, and the gauze is 

 moved in direct proportion to the distance the 

 recorder travels through the water. Sections of 

 the gauze are marked to correspond with previously 

 determined distances, depending on the size or 

 pitch of the propeller. For most collections, two 

 inches of gauze for each mile sampled are recom- 

 mended. The spools hold as much as 500 inches of 

 gauze which allow nearly 250 miles of continuous 

 data collection. As the gauze leaves the tunnel, 

 it is at once joined by a second gauze strip which 

 winds with it onto the storage spool in the forma- 

 lin tank. This second strip prevents the plankton 

 from being rubbed from one part of the roll to 

 another. 



This sampler has the advantage of being able 

 to sample continuously for over two hundred miles 

 and will indicate horizontal distribution or 

 "patchiness" in plankton populations. 



However, this instrument has an even smaller 

 aperture than the CLARKE-BUMPUS sampler, and con- 

 sequently most macroplankton will avoid capture. 

 It is restricted to near-surface sampling and 

 crushes some of the larger zooplankton. (35) 



HAKMATTAN . The dry, dusty trade wind blowing off 

 the Sahara Desert across the Gulf of Guinea and 

 the Cape Verde Islands. Sometimes called the doc- 

 tor, because of its supposed healthful properties. 

 (17) 



HARMONIC. A harmonic is a sinusoidal quantity hav- 

 ing a frequency that is an integral multiple of the 

 frequency of a periodic quantity to which it is 

 related. (2) 



55 



