Part 5

Association. Mental connection. The word has also three or four meanings in chemistry, which cannot be explained briefly.

Asteroid. A minor planet.

Astronomy. The science of the heavenly bodies.

Astrophysics. The science which deals with the constitution of the heavenly bodies. It is a branch of astronomy.

Atmosphere. The gaseous envelope about a heavenly body. Especially the air which surrounds the earth. As a measurement, a pressure of fifteen pounds per square inch.

Atom. The smallest particle of an element that enters into combination. According to old definitions, it is indivisible.

Aurora. A luminous atmospheric phenomenon. The aurora borealis radiates from the north magnetic pole, the aurora australis from the south magnetic pole of the earth.

Avogadro’s Hypothesis. The assumption that equal volumes of gases contain equal numbers of molecules if conditions of temperature and pressure are the same. It appears to be close to the truth.

Axiom. A truth which is considered self-evident.

Bacillus. One of a sort of rod-shaped bacteria. Loosely, any bacterium. Plural: bacilli. The Oxford English Dictionary distinguishes bacillus from bacterium, “with which it agrees in its rodlike form, and characterized by its larger size and mode of reproduction.”

Bacterium. More familiar in plural: bacteria. A group of vegetable microörganisms. Not all cause disease.

Barbarian. Of a civilization intermediate between one which is called savage and the most complex forms.

Barium. A silver-white element, classed as a metal. Symbol: Ba.

Barometer. An instrument used to measure atmospheric pressure, and thus to predict storms or determine altitudes.

Base. A substance which can neutralize acids to form a salt. The term includes alkalis. Part of an organ (of a plant or animal) attached to another organ which is more central.

Batrachia. An order of amphibians which have no tails in the adult stage.

Battery. A system of cells (sometimes used for a single cell) which changes chemical energy into electricity.

Becquerel rays. Rays emitted by radium and other substances which are susceptible to deflection by electricity and which electrically charge other bodies.

Behaviorism. Watson’s psychological system. Opposed to introspective psychology, and it emphasizes the physiology of human behavior.

Bessemer steel. Steel made from cast iron by a process which burns out carbon, sulphur, and phosphorus.

Beta rays. Becquerel rays which are apparently identical with cathode rays.

Bichloride. A compound in which there are two atoms of chlorine in the molecule.

Biennial. A plant that rises one year and flowers, fructifies, and dies the next.

Binary. Composed of two elements.

Biochemistry. The chemical study of living organisms and their products.

Biology. The science of living organisms.

Biophore. The indivisible unit of life. The biophore cannot support life if split up.

Bird. One of a class of feathered and warm-blooded vertebrate animals.