A scale of yellows, greens, and blues for recording the color of sea water, as seen against the white background of a Secchi disk.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

A white disk 12" or more in diameter which is lowered into the sea to estimate transparency of the water. The depths are noted at which it first disappears when lowered and reappears when raised.

A precipitation amount of less than 0.005 inches. Also, the record made by any self-registering instrument.

A balloon designed to float at a constant pressure level. This may be accomplished by a pressure valve which controls the release of ballast so as to maintain flight above a selected pressure level until the supply of ballast is exhausted. See Moby Dick b ...

Temperarure at which a liquid solidifies under any given set of conditions. It may or may not be the same as the melting point or the more rigidly defined true freezing point or (for water) ice point.

A hypothetical temperature characterized by a complete absence of heat and defined as 0 K, -273.15 C, or -459.67 F.

Similar to the spectroheliograph, but used for visual instead of photographic purposes.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

An instrument used to measure the water vapor content of the air.

An instrument used to measure changes in the level of the water in an evaporation pan. The gauge is normally placed in a Stillwell and adjusted so that the point of the hook just breaks the water surface. The change in water level is read on the attached ...

An instrument whose calibration is determined by comparison with an absolute instrument.

A high-altitude sounding system consisting of a small solid- propellant research rocket carried aloft by a large plastic balloon. The rocket is fired near the maximum altitude of the balloon flight.

Any emission of light at temperatures below that required for incandescence.

A subtle, diumal component of the wind velocity leading to a diumal shift of the wind or turning of the wind with the sun, produced bv the east-to-west progression of daytime surface heating.

A photometric unit of illuminance or illumination equal to one lumen per square meter

The average temperature of the air as indicated by a properly exposed thermometer for a given time period, usually a day, a month, or a year.

The total area drained by a river and its tributaries. Same as river basin.

Snow gauge composed of a metal cylinder, closed at one end, used to obtain a sample of snow from which the water is measured after melting.

A mercury barometer designed for use aboard ship. The instrument is of the fixed-cistern type (see Kew barometer). The mercury tube is constructed with a wide bore for its upper portion and with a capillary bore for its lower portion. This is done to incr ...