Air Thermometer. Thermometer filled with dry air. Expansion and contraction of enclosed air, due to heat content, are measured by pressure required to keep the volume at a constant value. Pressure thus indicates temperature. Range is exceedingly large, readings to - 300°F being obtainable.
Airy's Figure of Earth.Dimensions of Earth as computed by Sir George Airy (1801-1892), Astronomer Royal. Equatorial diameter 20,923,715 ft, polar diameter 20,853,810 ft., compression 1/2293 Used in British Ordnance Survey.
Airy's Method of Great Circle Sailing. Used for finding position of mid-point in a great circle course between two places when rhumb line is laid off on a Mercator chart. Rhumb line is bisected and a perpendicular to it is extended towards or through Equator. Tables then give latitude in which the great circle course cuts the perpendicular.