_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. _Bisexual._ Pertaining to, or containing the organs of, both sexes. _Bismuth._ A metallic element. Symbol: Bi. _Boron._ A non-metallic solid element. Symbol: B. _Botany._ The science of plants. _Boyle’s Law._ The theory that the pressure exerted by air is directly proportional to its density. This is now believed to be true only approximately. _Brachycephalic._ Pertaining to skulls of which the breadth is at least four-fifths of the length. Short-headed. _Brass._ An alloy of copper and zinc. _British Thermal Unit._ The amount of heat which is capable of raising the temperature of one pound of water by one degree Fahrenheit. The usual abbreviation: B.T.U. _Bromine._ A liquid element. Symbol: Br. _Bronze._ An alloy of copper and tin, usually with small amounts of zinc. _Brownian movement._ A movement of minute drops of oil suspended in stagnant air, apparently due to molecular motion. _Bunsen burner._ A sort of burner much used by chemists, within which air and fuel gas are mixed. _Burn._ To oxidize in such a way that heat and light are produced. _Cadmium._ A metallic element. Symbol: Cd. _Caesium._ A metallic element. Symbol: Cs. It somewhat resembles potassium. _Calcium._ A metallic element. Symbol: Ca. Compounds of calcium are common, but the element is not to be found in a pure state. _Calculus._ Solid concretion in the body. A branch of mathematics, differential and integral calculus, which deals with problems of constant variation or motion, and which has been of great importance in modern science. _Calorie._ The unit of heat, the amount of heat necessary to raise the temperature of a gram of water one degree Centigrade. This is the small calorie. Confusion sometimes results because the large calorie, which is one thousand times the small one, is called simply the calorie, without any qualification, in discussions about food. It is sometimes known as the great calorie. The small calorie is best called the gram-calorie. _Calorimeter._ An instrument for measuring quantities (not degrees) of heat. _Calyx._ The outer case of a bud. _Cambrian._ Relating to the lowest of the Paleozoic rocks and the earliest part of the Paleozoic period. _Candlepower._ The unit of illumination, measured by a standard candle. The illumination produced one foot away from a standard candle is the candle foot. _Capillarity_ or _capillary attraction_. A phenomenon best illustrated in very slender (capillary) tubes, in which the liquid rises, or, if it does not wet the tube, sinks. In the latter case we speak of capillary repulsion. _Capital._ In economics, wealth employed for the purpose of production. _Carbolic acid._ Phenol, not a true acid. _Carbon._ An element which exists in three allotropic forms. Symbol: C. The oxides are important, and there are many organic compounds.