distance (in.) or reduction of thickness (7.) 

 represented by the difference between the beginning 

 and end of the damped sinusoidal curve after a 

 specified time. Creep of hard rubber is measured 

 as Cold Flow. A Creep design chart may be con- 

 structed by plotting stress vs log of time for 

 each of a series of limiting deformations. From 

 such a chart. Creep Strength for various limiting 

 deformations may be determined. Creep Rate and 

 Creepocity may also be determined from Creep data. 



CREO . Centre de Recherches et d Etudes Oceano- 

 graphiques . 



CREST LENGTH. WAVE . The length of a wave along its 

 crest. Sometimes called crest width. (11) 



CREST OF WAVE . 1. The highest part of a wave. 

 2. That part of the wave above 

 STILL WATER LEVEL. (11) 



CSAGI . Special Committee for the Annual Geo- 

 physical International. 



CSAGY . Special Committee for International Geo- 

 physical Year. 



CSI RO. Commonwealth Scientific and Industrial 

 Research Organization. (Australia) 



CSK. Cooperative Study of the Kuroshio and Ad- 

 jacent Regions. 



CTCA. Commission for Technical Cooperation for 

 Africa South of the Sahara. 



CUBMARINE PC-3B . A manned submersible vehicle (US), 



CUBMARINE PC-3X . A manned submersible vehicle (US). 



CREST WIDTH . See CREST LENGTH, WAVE. 



CREVICE CORROSION . Corrosion which occurs within 

 or alongside a crevice formed by contact with 

 another piece of the same or another metal or with 

 a non-metallic material. (35) 



CRITICAL DAMPING . Critical damping is the minimum 

 viscous damping that will allow a displaced system 

 to return to Its initial position without oscil- 

 lation. (2) 



CRITICAL SPEED . Critical speed is a speed of a 

 rotating system that corresponds to a resonance 

 frequency of the system. (2) 



CROMWELL C U RRENT . An equatorial undercurrent in 

 the Pacific Ocean, discovered in 1952 by Townsend 

 Cromwell. The three other members of the Pacific 

 Equatorial Current System (known for a century) 

 are: the North Equatorial Current, Equatorial 

 Countercurrent , and South Equatorial Current. 



CROSS SEA . A series of waves or swell crossing 

 another wave system at an angle. (17) 



CROSS TIDE . A tidal current setting In a direction 

 approximately 90° from the course of a vessel. One 

 setting in a direction approximately 90° from the 

 heading is called a beam tide. In common usage 

 these two expressions are usually used synonymously. 

 One setting in a direction approximately opposite 

 to the heading is called a head tide. One setting 

 in such a direction as to increase the speed of a 

 vessel is called a fair tide. (17) 



CRPAO. Commission Reglonale des Peches pour 

 L'Afrlque de L'OUEST. 



CRUDES PAG . Cruiser-Destroyer Forces, Pacific (USN) . 



CRULANT . Cruiser Forces, Atlantic (USN). 



CRYOGENIC SWITCHING ELEMENTS . In Information 

 processing, logical switching Information process- 

 ing elements which utilize the variability of the 

 transition to superconductivity as a function of 

 magnetic field strength. 



CRYSTAL. A natural substance, such as quartz or 

 tourmaline, which is capable of producing a voltage 

 stress when under pressure, or producing pressure 

 when under an applied voltage. Under stress It 

 has the property of responding only to a given 

 frequency when cut to a given thickness. It is 

 therefore a valuable medium to control the frequen- 

 cy of audio transmitters. (10) 



CRYSTALLOGRAPHY . 

 of crystals. 



The study of the characteristics 



CUM SOLE . See CONTRA SOLEM. 



CUMULONIMBUS . A massive cloud with great vertical 

 development, the summits of which rise in the form 

 of mountains or towers, the upper parts having a 

 fibrous texture and often spreading out In the shape 

 of an anvil. Cumulonimbus generally produces show- 

 ers of rain, snow, or hall, and often thunderstorms. 

 Sometimes called thundercloud. (17) 



CUMULUS . A dense cloud with vertical development, 

 having a horizontal base and dome-shaped upper sur- 

 face, exhibiting protuberances. When the cloud Is 

 opposite the sun, the edges appear darker than the 

 center, while against the sun the opposite is true; 

 when the light comes from the side, the cloud ex- 

 hibits strong contrasts of light and dark. (17) 



CURRENT . A horizontal movement of the water. 

 Currents may be classified as tidal and nontidal. 

 TIDAL CURRENTS are caused by the tide-producing 

 forces of the moon and sun and are a part of the 

 same general movement of the sea that is manifested 

 in the vertical rise and fall of the tides. Non- 

 tidal currents include the permanent currents In 

 the general circulatory systems of the sea as well 

 as temporary currents arising from meteorological 

 conditions. (14) 



CURRENT, COASTAL , One of the offshore currents 

 flowing generally parallel to the shore line with 

 a relatively uniform velocity (as compared to the 

 LITTORAL CURRENTS). They are not related genetical- 

 ly to waves and resulting surf but may be composed 

 of currents related to distribution of mass in 

 ocean waters (or local eddies), wind-driven cur- 

 rents and/or tidal currents. (11) 



CURRENT DRIFT , A broad, shallow, slow-moving ocean 

 or lake current, (11) 



CURRENT. EBB , The movement of the tidal current 

 away from shore or down a tidal stream. (11) 



CURRENT, EDDY . A circular movement of water of 

 comparatively limited area formed on the side of a 

 main current. Eddies may be created at points 

 where the main stream passes projecting obstruc- 

 tions. (11) 



CURRENT ELLIPSE . A graphic representation of a 

 ROTARY CURRENT in which the velocity and direction 

 of the current at different hours of the tidal 

 cycle are represented by radius vectors and vec- 

 torial angles. A line joining the extremities of 

 the radius vectors will form a curve roughly ap- 

 proximating an ellipse. The cycle is completed in 

 one-half tidal day or In a whole tidal day accord- 

 ing to whether the current is of the semidiurnal or 

 the diurnal type. A current of the mixed type will, 

 give a curve of two unequal loops each tidal day. (14) 



29 



