RIPARIAN . Pertaining to the banks of a body of 

 water. (11) 



RIPARIAN RIGHTS . The rights of a person owning 

 land containing or bordering on a watercourse or 

 other body of water in or to its banks, bed, or 

 waters. (11) 



RIP CURRENTS . A strong surface current of short 

 duration flowing seaward from the shore. It usual- 

 ly appears as a visible band of agitated water and 

 is the return movement of water piled up on the 

 shore by incoming waves and wind. With the seaward 

 movement concentrated in a limited band its velocity 

 is somewhat accentuated. A rip consists of three 

 parts: The feeder current flowing parallel to the 

 shore inside the breakers; the neck, where the 

 feeder currents converge and flow through the 

 breakers in a narrow bank or "rip"; and the head, 

 where the current widens and slackens outside the 

 breaker line. A rip current is often miscalled a 

 rip tide. (11) 



RIPPLE MARKS . Small, fairly regular ridges in the 

 bed of a waterway or on a land surface caused by 

 water currents or wind. As their form is approxi- 

 mately normal to the direction of current or wind, 

 they indicate both the presence and the direction 

 of currents or winds. (11) 



RIPRAP . A layer, facing, or protective mound of 

 stones randomly placed to prevent erosion, scour, 

 or sloughing of a structure or embankment; also 

 the stone so used. (11) 



RIP SURF . See CURRENT, RIP. 



RISE . A long, broad elevation that rises gently 

 and generally smoothly from the sea floor. (26) 



ROAD . See ROADSTEAD, 



ROADSTEAD . An area near the shore, where vessels 

 can anchor in safety; usually a shallow indenta- 

 tion in the coast. One with relatively little 

 protection may be called open roadstead. Also 

 called road. (17) 



ROARING FORTIES . The area of the oceans between 

 40" and 50° south latitude, where strong westerly 

 winds prevail. See BRAVE WEST WINDS. (17) 



ROBERTS RADIO CURRENT METER . The Roberts Radio 

 Current Meter is an instrument designed specifical- 

 ly to record subsurface current speeds accurately 

 and simultaneously indicate the direction of the 

 flow. The basic components consist of a buoy from 

 which 1 to 3 meters may be suspended, an automatic 

 radio-transmitting system within the buoy, and a 

 ship- or shore-based radio-receiving monitoring 

 system which can monitor up to 15 meters. The 

 buoys usually are anchored in bays, rivers, channels, 

 or other relatively shallow areas. Meters have 

 been operated successfully at depths as great as 

 2,500 meters from anchored ships. 



The current meter is suspended at any desired 

 depth from a buoy of special design which cbntains 

 a battery-powered radio transmitter and selecting 

 device and supports an antenna and warning lights. 

 The meter aligns itself to the direction of the 

 current flow. The current drives an impeller, or 

 screw, in the nose of the meter. The impeller is 

 connected by a magnetic drive through a watertight 

 bulkhead to an enclosed mechanism which makes and 

 breaks an electrical circuit by means of two con- 

 tacting devices. One device makes a contact at 

 each fifth turn of the impeller and the other 

 every tenth turn. The frequency ot the contacts 

 serves as a measure of velocity. The first con- 

 tacting device is connected with a built-in mag- 

 netic compass and the second is fixed relative to 

 the position of the meter body. The contacting 

 mechanisms are so arranged that when the instrument 



is heading south both contacts will close at the 

 same time. When the meter heads in any other direc- 

 tion the time relation between the two sets of con- 

 tacts changes with the meter heading. This serves 

 as a measure of direction. The contact makes and 

 breaks, relating to direction and speed, are re- 

 layed via watertight electrical cable to the buoy 

 where the transmitter is keyed to produce radio 

 signals on a designated frequency. The operating 

 frequency is controlled by a crystal selected for 

 maximum results in the specific area. These sig- 

 nals are received, amplified, and recorded on tape 

 by means of a chronograph at the ship- or shore- 

 based monitoring station. Observers at the moni- 

 toring station record the signals on tape from 

 several current meter stations by adjusting the 

 receiver to different frequencies at timed intervals. 

 (35) 



ROCHELLE SALT AND ADP PROJECTORS , In this type 

 projector, the plates of Rochelle salt and ADP 

 crystals are mounted so as to utilize the length 

 vibrations instead of the thickness vibrations. 

 The two large faces are coated with a metal foil. 



and the ac voltage is applied to the foil. The 

 arrows indicate the deformation resulting from the 

 indicated charge. The crystals are cemented to a 

 single backing plate. The sound is radiated from 

 the free ends of the crystal. The longitudinal 

 vibration is the one desired. (30) 



ROCK . (1) Engineering - A natural aggregate of 

 mineral particles connected by strong and permanent 

 cohesive forces. In igneous and metamorphic rocks, 

 it consists of interlocking crystals; in sedimentary 

 rocks, of closely packed mineral grains, often 

 bound together by a natural cement. Since the terms 

 "strong" and "permanent" are subject to different 

 interpretations, the boundary between rock and soil 

 is necessarily an arbitrary one. 



(2) Geological - The material that forms the 

 essential part of the earth's solid crust, and 

 includes loose incoherent masses, such as a bed of 

 sand, gravel, clay or volcanic ash, as well as the 

 very firm, hard and solid masses of granite, sand- 

 stone, limestone, etc. Most rocks are aggregates 

 of one or more minerals but some are composed en- 

 tirely of glassy matter, or of mixtures of glass 

 and minerals. (27) 



ROLL . Athwartship (i.e., transverse) oscillation 

 of a ship about its longitudinal axis. (12) 



ROCKWEED . See FUCUS . 



ROLLER . 1, SWELLS coming from a great distance 

 and forming large breakers on exposed coasts. 



They are best known on the islands of St. 

 Helena and Ascension in the South Atlantic Ocean 

 during the months from December to April, when 

 they come from the northwest. They arrive, often 

 in calm weather, with practically no warning, and 

 are dangerous to shipping. Rollers also occur 

 at Fernando do Noronha, Tristan da Cunha, and on 

 the coasts of West Africa, Peru, and the East 

 Indies, (24) 



2, A long, massive wave which usually 

 retains its form without breaking until it reaches 

 the beach or a shoal, (17) 



101 



