ference between the two disks acts on the thermo- 

 pile and produces an electromotive force (EMF) 

 which is proportional to the intensity of the in- 

 cident radiation. This EMF is transmitted to a 

 recording potentiometer. 



See also PYRHELIOMETER . (35) 



RED CLAY . A fine-grained deposit that is predomi- 

 nantly clay, of low carbonate and silica content, 

 that covers most of the deeper portions of the 

 ocean basins. Also called BROWN CLAY. (27) 



RED MUD . A reddish-brown terrigenous deep-sea mud 

 which accumulates on the sea floor in the neigh- 

 borhood of deserts and off the mouths of great 

 rivers; contains calcium carbonate up to 25 per 

 cent. (27) 



RED TIDE . A growth of DINOFLAGELLATES (single- 

 celled plant-like animals) in surface waters in 

 such quantities as to color the sea red and kill 

 fish. (24) 



REEF . An offshore consolidated rock hazard to 

 navigation with a least depth of ten fathoms or 

 less. (27) 



REEF BARRIER (BARRIER REEF) . A reef which roughly 

 parallels land but is some distance offshore, with 

 deeper water intervening. (27) 



REFERENCE PLANE (DAILY HATER) . The plane to which 

 sounding and tidal data are referred . The follow- 

 ing reference planes are used by various countries: 

 MEAN LOW WATER - United States (Atlantic Coast), 



Argentina, Sweden and Norway. 

 MEAN LOWER LOW WATER - United States (Pacific 



Coast), including Alaska and Island Possessions. 

 MEAN LOW WATER SPRINGS - Great Britain, Germany 



Italy, Brazil and Chile. 

 LOWEST LOW WATER SPRINGS - Portugal. 

 INDIAN SPRING LOW WATER - India and Japan. 

 LOWEST LOW WATER - France, Spain and Greece. 

 MEAN LAKE LEVEL - Great Lakes of U. S. and Canada. 

 MEAN SEA LEVEL - Used in Denmark. 



See also DATUM PLANE. (27) 



REFERENCE STATION . A station for which tidal con- 

 stants have previously been determined and which is 

 used as a standard for the comparison of simultane- 

 ous observations at a second station; also a station 

 for which independent daily predictions are given 

 in the tide or current tables from which correspond- 

 ing predictions are obtained for other stations by 

 means of differences or factors. (11) 



REFLECTED WAVE . The wave that is returned seaward 

 when a wave impinges upon a very steep beach, bar- 

 rier, or other reflecting surfaces. (11) 



REFLECTION LOSS . The reflection loss at the junc- 

 tion between an energy source and an energy load is 

 the transmission loss measured by the ratio of (1) 

 the load power which would be measured if source 

 and load were connected by a hypothetical trans- 

 ducer having an input impedance equal to the load 

 impedance of the load, and developing the same 

 volt-amperes at its load terminals as are developed 

 at its source terminals, to (2) the actual load 

 power when source and load are connected directly 

 to each other. (4) 



REFRACTION COEFFICIENT . The square root of the 

 ratio of the spacing between adjacent orthogonals 

 in deep water and in shallow water at a selected 

 point. When multiplied by the SHOALING FACTOR, 

 this becomes the WAVE HEIGHT COEFFICIENT or the 

 ratio of the refracted wave height at any point to 

 the deep water wave height. Also the square root 

 of the ENERGY COEFFICIENT. (11) 



REFRACTION DIAGRAM . A drawing showing positions of 

 wave crests and/or orthogonals in a given area for 

 a specific deep water wave period and direction. (11) 



REFRACTION LOSS . Refraction loss is that part of 

 the transmission loss which is due to refraction in 

 the medium. These losses arise from nonunlformities 

 in the medium. (9) 



REFRACTION OF WATER WAVES . (1) The process by 

 which the direction of a wave moving in shallow 

 water at an angle to the contours is changed. The 

 part of the wave advancing in shallower water moves 

 more slowly than that part still advancing in deeper 

 water, causing the wave crest to bend toward align- 

 ment with the underwater contours. (2) The bending 

 of wave crests by currents . (11) 



REGULAR LAY . See WIRE ROPE. 



RELATIVE DEPTH . Ratio of the wavelength to the 

 water depth. 



RELATIVE PRESSURE FIELD . The pressure field that 

 would be present if the pressure distribution 

 depended only upon the distribution of mass in 

 the sea. 



RELATIVE PRESSURE RESPONSE . It is possible to mea- 

 sure the relative response of a projector in terms 

 of acoustic pressure, as well as in terms of acous- 

 tic intensity. When so measured the relative 

 response of a projector is known as its relative 

 pressure response. (4) 



RELATIVE RECEIVING RESPONSE . The relative receiv- 

 ing response of a hydrophone, for any bearing and 

 for any frequency, may be defined as the ratio of 

 the receiving response for that bearing and that 

 frequency to the receiving response for a specified 

 bearing and a specified frequency. (4) 



RELATIVE RESPONSE . The relative response of a 

 transducer, in decibels, is the amount by which the 

 response under some particular condition exceeds 

 the response under a reference condition that should 

 be stated explicitly. (1) 



RELATIVE TRANSMITTING RESPONSE . The relative 

 transmitting response of a sonar projector, for any 

 bearing and for any frequency may be defined as the 

 ratio of the transmitting response for that bearing 

 and that frequency to the transmitting response for 

 a specified bearing and a specified frequency. (4) 



REPRODUCTIVE EURYHALINE . See STENOHALINE. 



REPRODUCTIVE STENOHALINE. See STENOHALINE. 



RES A. 



Scientific Research Society of America. 



RESEARCH . A process of scientific investigation 

 prior to and during development. It has for its 

 aim the discovery of new scientific facts, tech- 

 niques, and natural laws; an extension of the 

 "state-of-the-art." (42) 



RESEARCH. APPLIED . Research aimed at specific 

 application of scientific laws, principles, and 

 phenomena. In contrast to basic research, the 

 prospect of practical application of the results 

 is a primary motive for applied research. Fre- 

 quently even the methods to be used are clear 

 before work is begun. (42) 



RESEARCH. BASIC . The theoretical or experimental 

 study directed toward the increase of knowledge. 

 It may result in the discovery of new scientific 

 phenomena, principles, techniques, or significant 

 data which add to the store of scientific knowledge. 

 Immediate practical application is not necessarily 

 a direct objective. (42) 



RESIDUAL VOLUME . In physiology - the amount of air 

 that remains in the lungs even after the most force- 

 ful expiration. It normally amounts to between 1 



