273 GLOSSARY GLOSSARY Charles’ Law: For any gas at a constant pressure, the volume of the gas will vary directly with the absolute temperature. Chart: The equivalent of a map for bodies of water and the adjacent coastlines. Circular search: Where two divers search an area in a circular pattern, using a line for reference. Closed-circuit scuba: A system in which all exhaled breath is recirculated within the system and rebreathed. Collapsing breakers: A type of surf forming from medium swells breaking over a very steep bottom. The waves break over the lower halves of themselves with very little splash or foaming. Compass card: A magnetized disc within a compass which rotates to indicate a northerly direction. Conduction: The transmission of heat by direct material contact. Conservation: Management of human usage of the waters so they may yield the greatest sustainable benefit to present and future generations. Preserving, guarding, or protecting natural resources. Console: A housing for two or more diving instruments. Contour search: Where divers follow a constant depth along the bottom. Convection: The transmission of heat by the movement of heated fluids. Coriolis force: Deflection of winds and currents caused by the rotation of the Earth. Cramp: A muscle spasm producing pain and temporary disability. Cylinder: A vessel that holds matter under pressure. Cylinder pressure gauge: An instrument used to measure air pressure in a cylinder above water. D Dalton’s Law: The total pressure exerted by a mixture of gases is equal to the sum of the pressures that would be exerted by each of the gases if it alone were present and occupied the volume. Dead reckoning: Navigation by means of estimating distance and direction. Deep air diving: Practiced by technical divers to depths up to 60 m (200 feet). Dehydration: Abnormal loss of fluid from the body. Density: The mass or weight of a substance per unit volume. Deviation: Error induced in a compass needle reading by the effect of nearby metal or a magnetic source. Dew point: The temperature to which air must be cooled, at a constant pressure, in order to become saturated with water and below which condensation occurs. Diaphragm depth gauge: An instrument that uses the movement of a metal diaphragm in conjunction with mechanical linkage to indicate depth. Diffusion: The scattering of light. Also the movement of molecules in a liquid or gas from a region of high concentration to a region of lower concentration. Digital depth gauge: An instrument that uses a pressure transducer, electronics, and a battery to display depth in a digital form. DIN valve: Scuba cylinder on/off valve with threaded regulator attachment. Dive computer: An instrument that continuously calculates time and depth and provides a digital display of a diver’s decompression status. Dive flag: Flown to warn boaters and others that divers are in or under water in the vicinity. Dive pattern: The total course or dive path followed
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