=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.
=Aurora Borealis= (_bō´rẽ-ā´lĭs_), i. e., northern daybreak; popularly called northern lights. A luminous meteoric phenomenon, visible only at night, and supposed to be of electrical origin. This species of light usually appears in streams, ascending toward the zenith from a dusky line or bank, a few degrees above the northern horizon. Occasionally the aurora appears as an arch of light across the heavens from east to west. Sometimes it assumes a wavy appearance. They assume a variety of colors, from a pale red or yellow to a deep red or blood color.
The =Aurora Australis= (_aws-trā´lĭs_) is a corresponding phenomenon in the southern hemisphere, the streams of light ascending in the same manner from near the southern horizon.
=Barometer= (_bȧ-rŏm´ẽ-tẽr_).--An instrument for determining the weight or pressure of the atmosphere, and hence for judging of the probable changes of weather, or for ascertaining the height of any ascent.
=Calamites= (_kal´a-mīts_ or _kal´a-mī´tēz_).--Reed-like plants, found in coal.
=Carboniferous= (_kär´bŏn-ĭf´ẽr-ŭs_).--Producing or containing carbon or coal.
=Conglomerate= (_kŏn-glŏm´ẽr-ât_).--Pudding stone, composed of gravel and pebbles cemented together.
=Corona= (_kô-rō´nȧ_).--A circle, usually colored, seen in peculiar states of the atmosphere around and close to a luminous body as the sun or moon.
=Cosmogony= (_kŏs-mŏg´o-ny̆_).--The creation of the world or universe; a theory or account of such creation.
=Cosmology= (_kŏz-mŏl´ô-jy̆_).--The science of the world or universe; or a treatise relating to the structure and parts of the system of creation, the elements of bodies, the modifications of material things, the laws of motion, and the order and course of nature.