to the echo from a six-foot diameter perfectly re- 

 flecting sphere at the same range and depth. (7) 



TECTIN . The organic material in skeletons of some 

 PROTOZOANS; pseudochitin. (19) 



TECTOGEN . The down-buckled root of a geosynclinal 

 trough. See also GEOSYNCLINE. (27) 



TECTONIC. An adjective pertaining to or designat- 

 ing structures resulting from deformation of the 

 earth's crust. (27) 



TECTONO-EUSTATISM . See EUSTATISM. 



TEHUANTEPECER . A violent north wind frequent in 

 the winter in the region around the Gulf of 

 Tehuantepec in Mexico. (17) 



TELECHIRIC . A word formed by two Greek words, 

 tele, meaning distant and kheir which means, hand. 

 Telechiric is used to mean the technology of 

 manipulation at a distance and with no direct con- 

 nection between the operator and his machine or 

 tools. Such fully controlled uninhabited mechani- 

 cal devices can be effectively used in oceano- 

 graphic and OCEAN ENGINEERING work. 



TELEGRAPH BUOY . A buoy used to mark the position 

 of a submarine telegraph cable. (17) 



TELEMETERING THERMOMETER . This is a temperature 

 TRANSDUCER for temperature measurement at depth, 

 working in conjunction with a radio telemetering 

 link ^rom a drift buoy, allowing identification of 

 the body of water in which the buoy rests at the 

 time of observation. Sometimes used to determine 

 whether the buoy has remained with the water mass 

 in which it was deposited or conversely to know 

 some parameter of the water immediately under it. 

 The normal design depth is 200 meters where surface 

 disturbances are not felt. (30) 



TELEMETERING WAVE BUOY (SPLASHNDC) . A device 

 similar to the floating ACCELEROMETER with one sig- 

 nificant difference. This unit transmits its ver- 

 tical acceleration signals back to a ship by radio, 

 eliminating any ship motion from being imparted to 

 the buoy. The system consists of a buoy assembly 

 containing a transducer and transmitter, a wide- 

 band FM receiver, an electronic low-pass filter, 

 and a recorder. The transmitter sends a signal 

 that varies in frequency proportional to the accel- 

 eration experienced by the buoy assembly. This sig- 

 nal is received by an antenna mounted on a ship and 

 is fed into the FM receiver. In the receiver the 

 frequency changes are converted to a varying d.c. 

 voltage which is proportional to the acceleration. 

 The d.c. voltage is placed on the input of the ad- 

 justable low-pass filter which cuts off the sig- 

 nals produced by the surface chop of the sea, but 

 passes unaltered the lower-frequency signals pro- 

 duced by the larger and longer waves. The output 

 of the filter unit then is recorded either on mag- 

 netic tape or on a direct-writing recorder. The 

 surface wave record is obtained by a double inte- 

 gration of this output. 



This wave buoy was not designed to be a re- 

 fined instrument; the cost has been kept at around 

 $100 to $200, and it probably could be brought 

 lower by mass production. Thus the buoy can be 

 considered as expendable if necessary. The trans- 

 mitter is subject to some frequency drift, and the 

 tuner needs occasional retuning. An error exists 

 in the acceleration information obtained, because 

 the lever arm of the accelerometer does not remain 

 horizontal as the float assembly rides up and down 

 the waves . (35) 



TELEMETRY . The science involved with measuring a 

 quantity or quantities, transmitting this value to 

 a station, and there interpreting, indicating, or 

 recording the quantities. 



The oceanographer may utilize radio and acous- 

 tic links or electrically insulated wire devices 

 to transmit telemetered information. 



TELERECORDING BATHYTHERMOMETER . The bathyther- 

 mometer is a 2-unit transistorized system, operated 

 like a BT, which gives a plot of temperature vs 

 depth. The absolute accuracy in depth reportedly 

 is better than +0.25 per cent, or +2.5 feet in 

 1000 feet, temperature sensitivity is 0.05°C. A 

 vibrating wire transducer (Vibrotron) and ther- 

 mistor Wien-bridge oscillator provide for depth 

 and temperature respectively. This device, devel- 

 oped by Snodgrass and Cawley employs a thermistor 

 as temperature-sensing element. The data are 

 telemetered from depth over a single polyethylene- 

 insulated wire to a ship. This method can be used 

 to telemeter additional information. (35) 



TELERECORDING CURRENT DIRECTION TRANSDUCER . The 

 underwater unit of this instrument transmits ocean 

 current direction to the surface over a single con- 

 ductor insulated cable, sea-return system. Eight 

 underwater units may be suspended and operated 

 simultaneously over a single conductor cable. 

 Basic underwater data is photoelectric position 

 information obtained from a precision mounted, 

 viscous damped magnetic compass element. Data 

 transmission is P.D.M. (Pulse Duration Modulation) 

 by F.S.K. (Frequency Shift Keyed) on standard 

 channels 6 through 13. Power is supplied to 4 

 surface modules and the underwater unit. Each 

 plug-in module contains a hand pass filter, limiter, 

 discriminator, and P.D.M. data conversion circuits. 

 A meter on each module indicates current direction. 

 (30) 



TELLURGMETER . The Tellurometer is a phase com- 

 parison base line measuring system which was de- 

 veloped in the Union of South Africa and is now 

 widely used over the world for geodetic surveying. 

 Radar frequencies are used to carry the distance 

 information and the system used 10 megacycles as 

 the basic measure-frequency so that the line width 

 is approximately 15 meters . (35) 



TEMPERAYURE-CHLORINITY-DEPTH RECORDER . The three 

 quantities are recorded sequentially by a single- 

 pen strip chart recorder, each quantity being re- 

 corded for five seconds at a time. The underwater 

 unit is suspended by means of an armored steel 

 cable which has a single electrically insulated 

 core. This core carries power down to the under- 

 water unit and brings up the signals from the mea- 

 suring elements. A simple frequency modulation 

 method of telemetering is used. 



Chlorinity is measured by means of a conduc- 

 tivity cell with platinized electrodes. The effect 

 of temperature on conductivity is compensated by 

 using a THERMISTOR. (35) 



TEMPERATURE OF THE OCEAN (General) . Temperature in 

 the ocean varies widely, both horizontally and with 

 depth. Maximum values of about 90 degrees F are 

 encountered in the Persian Gulf in summer, and the 

 lowest possible values of about 28 degrees F (the 

 usual minimum freezing point of sea water) occur 

 in polar regions . 



The vertical distribution of temperature in 

 the sea nearly everywhere shows decrease of tem- 

 perature with depth. Since colder water is denser, 

 it sinks below warmer water. This results in a 

 temperature distribution just opposite to that in 

 the earth's crust, where temperature increases 

 with depth below the surface of the ground. 



In general, in the sea there is usually a 

 mixed layer of isothermal water below the surface, 

 where the temperature is the same as that of the 

 surface. This layer is best developed in the 

 trade-wind belts, where it may extend to a depth 

 of 100 fathoms; in temperate latitudes in the 

 spring, it may disappear entirely. Below this 

 layer is a zone of rapid temperature decrease, 

 called the THERMOCLINE, to the temperature of the 



118 



