THERMOMETER FRAME 



thermometer frame — A frame designed to hold 

 2, 3, and in some cases 4 reversing thermome- 

 ters. It can be quickly attached to or removed 

 from a Nansen bottle. The frame consists of 

 tubes arranged for reading the thermometers 

 and perforations to permit water circulation 

 around the mercury reservoir. 



thermometer reader C viewer — A 6-X lense 

 mounted in a tube for ease and increased ac- 

 curacy in reading reversing therometer tem- 

 peratures. 



thermometric conductivity — (also called thermal 

 difliMsivity, heat conductivity) . The ratio of the 

 thermal conductivity of a substance to the 

 product of its specific heat and its density. For 

 a fluid, c is the specific heat at constant pressure. 

 The thermometric conductivity determines the 

 rate of heating due to a given temperature dis- 

 tribution. (5) 



thermometric depth — The depth, in meters, at 

 which paired protected and unprotected ther- 

 mometers attached to a Nansen bottle are re- 

 versed. The difference between the corrected 

 readings of the 2 thermometers represents the 

 effect of the hydrostatic pressure at the depth 

 of reversal. This depth may then be determined 

 by formula or form a depth anomaly (aZ) 

 graph. Depths obtained by this means are of 

 greatest value when a wire angle occurs. 



thermometric scale — See temperature scale. 



thermonuclear reaction — ^A nuclear reaction in 

 which the energy necessary for the reaction is 

 provided by colliding particles that have kinetic 

 energy by virtue of their thermal agitation. 

 Such reactions occur at appreciable rates only 

 for temperatures of millions of degrees and 

 higher, the rate increasing, enormously with the 

 temperature. The energy of most stars is be- 

 lieved to be derived from exothermic thermo- 

 nuclear reactions. (70) 



thermoprobe — A transducer used to measure 

 temperature in situ of ocean bottom sediments at 

 depths beneath the bottom. Such measurements 

 when combined with heat conductivity informa- 

 tion provide a measurement of lieat flow through 

 the ocean bottom. (4) 



thermosteric anomaly — ^The specific volume- 

 anomaly (steric anomaly) that the sea watef 

 at any point would attain if the sea water were 

 brought isothermally to a pressure of one stand- 

 ard atmosphere. In other words, thermosteric 

 anomaly is the specific volume anomaly calcu- 

 lated for the given salinity and temperature but 

 for a standard pressure. (5) 



thick winter ice — Winter ice more tlian 30 cen- 

 timeters (12 inches) thick. (74) 



thorium series — The series of nuclides resulting 

 from the decays of Tli^^^ (41) 



thorofare — Deep channels in the lagoon marshes 

 behind barriers and spits. 



threshold depth — See sill depth. 



thurm — A ragged, rocky headland swept by the 

 sea. (2) 



tickle — Any narrow passage connecting two large 

 bodies of water. In the Gulf of St. Lawrence 

 it is restricted to an inlet between the sea and 

 a lagoon. (2) 



tidal basin — A basin affected by tides, particu- 

 larly one in which water can be kept at a desired 

 level by means of a gate. (68) 



tidal bore — See bore. 



tidal component — See partial tide. 



tidal constants — ^Tidal relations that remain es- 

 sentially the same for any particular locality. 

 Tidal constants are classed as harmonic and non- 

 harmonic, the harmonic constants consisting 

 of the amplitudes and epochs, and the nonhar- 

 monic constants including those values deter- 

 mined directly from observations, such as tidal 

 ranges and intervals. (68) 



tidal constituent — See constituent, partial tide. 



tidal correction — A correction applied to gravi- 

 tational observations to remove the effect of 

 earth tides on gravimetric observations. The 

 value of gravity at any point varies in a cyclical 

 manner during the course of a day due to the 

 changing positions of the sun and the moon 

 relative to the area being investigated. The 

 tidal correction is commonly included in the 

 drift correction and may be determined by a 

 series of observations at a fixed base station. 



tidal crack — See tide crack. 



tidal current — (sometimes called tidal stream). 

 The alternating horizontal movement of water 

 associated with the rise and fall of the tide 

 caused by the astronomical tide-producing 

 forces. 



In relatively open locations, the direction of 

 tidal currents rotates continuously through 360 

 degrees diumally or semidiumally. In coastal 

 regions, the nature of tidal currents will be de- 

 termined by local topography as well. See flood 

 current, ebb current, reversing current, ro- 

 tary current. (5) 



tidal current chart — A chart showing, by arrows 

 and numbers, the average direction and speed 

 of tidal currents at a particular part of the 

 current cycle. A number of such charts, one for 

 each hour of the current cycle, usually are pub- 

 lished together. A current diagram is a graph 

 showing average speeds of flood and ebb cur- 

 rents throughout the current cycle for a con- 

 siderable part of a tidal waterway. (68) 



tidal current curve — See current curve. 



tidal current cycle — ^The period which includes 

 a flood and an ebb from one high water to the 

 next succeeding high water. The duration of 

 a semidiurnal tide approximates 12.42 hours; 

 that of a diurnal tide approximates 24.84 hours. 

 See tide curve, tide cycle. 



tidal current diagram — See current diagram. 



tidal cycle — See tide cycle. 



tidal datum — See chart datum. 



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