Aërodynamics (ā-ẽr-ō-di-nam´iks).—The science which treats of the air and other gaseous bodies under the action of force, and of their mechanical effects.
Aërognosy (ā-ẽr-ŏg´nô-sy̆).—The science which treats of the properties of the air, and of the part it plays in nature.
Aërolite (ā´ẽr-ô-līt).—A stone, or metallic mass, which has fallen to the earth from distant space; a meteorite; a meteoric stone.
Aërology (ā-ẽr-ŏl´ôjy̆).—That department of physics which treats of the atmosphere.
Aerometer (ā´ẽr-ŏm´ê-tẽr).—An instrument for ascertaining the weight or density of air and gases.
Ammonites (am´mo-nitz).—Fossil mollusks of spiral form, found in all strata from the palæozoic to the chalk; very numerous, varying greatly in size; all now extinct; sometimes called snakestones.
Anemology (ăn-ĕ-mŏl´ô-jy̆).—The science of the wind.
Anemometer (ăn-ĕ-mŏm´ẽ-tẽr).—An instrument for measuring the force and velocity of the wind; a wind gauge.
Attrition (ăt-trĭsh´ŭn).—The act of rubbing together; friction; the act of wearing by friction, or by rubbing substances together; abrasion.
Aurora (aw-rō´rȧ).—The rising light of the morning; the dawn of day; the redness of the sky just before the sun rises.