This property of a gas is the weight of air or gas per unit volume. Unless specified, it refers in compressor practice to the weight per unit volume at conditions of total temperature, total pressure and composition which prevail at the compressor intake.

A curve illustrating the variation or spectral irradiance with wavelength.

A hygrometer which determines the amount of precipitable moisture in a given region of the atmosphere by measuring attenuation of radiant energy caused by the absorption bands of water vapor.

The monochromatic irradiance of a surface per unit bandwidth at a particular wavelength, usually expressed in Watts per square meter-nanometer bandwidth.

The ratio of energy reflected from a surface in a given waveband to the energy incident in that waveband.

Solar radiation of selected wavelengths.

A type of window glazing films used to block the infrared (heat) portion of the solar spectrum but admit a higher portion of visible light.

An instrument for taking photographs of an image of the sun in monochromatic light.

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

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

An instrument which measures the spectral distribution of the intensity of direct solar radiation.

see Solar Spectrum above.

The number of revolutions per minute of the compressor shaft.

A ball shaped buoy marking a navigational hazard.

An aggregate of iron or alloy carbides of essentially spherical shape dispersed throughout a matrix of ferrite.

An outrigger used to hold a block clear of a mast or of the ship's side.

Small hole bored in cask or barrel to allow air to enter when emptying.

To spill the sails is to take the wind out of the sails, either by heading up into the wind, or by easing the sheets to the point where the sails can hold no wind.

To empty the wind out of a sail.

A passage for surplus water to flow over or around a dam.