Aneroid barometer, 285*. Arc, the electric, 233-240*. Atoms, description of, 196; electrons and, 197; everything in the world made of, 310-311; in molecules, 311. Aurora Borealis, cause of, 193. Automobile, reason for cranking, 210; how made to go, 344-345. Automobile races, overcoming of centrifugal force in, 75*. Automobile tires, reason for wearing of, 80; blow-outs of, 348. Baking powder, chemical change by solution shown by, 349-350; elements of which made, 367-368. Baking soda, a common base, 356; testing with litmus paper, 359; neutralization of sour milk by, in cooking, 362; carbon dioxid in, 366-367. Ball bearings, used to diminish friction, 54-55. Balloon, expansion of, 17-18, 109*; reason for rising of, 26; filling of, with hydrogen, 301-304*. Barometer, use of, 280-285*. Bases, substances called, 355-358; litmus test for distinguishing from acids, 358-359; neutralization of, by acids, 360-364. Batteries, electric, 203-205*; different kinds of, 205*-207*; general principle of all, 206. Bell, electric battery for ringing, 204-205*; working of electric, 255*. Bending of light (refraction), 136-141*. Black, the absence of light, 164. Bleaching, process of, 326-327. Blow-out of tire, a real explosion, 348. Blue-flame heaters, 319. Blueness of sky, reason for, 169. Blueprints, making of, 330-331. Boiling and condensing, 107-115*. Borax bead test, 371*-372*. Brass, an alloy, 310. Bread making, chemical action in, 365. Breath, cause of visibility of, on cold days, 288, 289*. Bronze, an alloy, 310. Burning, explanation of, 308, 312-313. Calcium chlorid, 114. Camera, lens of, 143, 148; human eye as a small, 151*-153; explanation of, 327-332. Capillary attraction, 36*-40; difference between adhesion, cohesion, and, 47. Carbon, in electric battery, 203-206; resistance of, to electric current, 231; an element, 293, 299; one of chief elements in fuel, 315-316. Carbon dioxid, in seltzer siphon, 17; produced by joining of carbon with oxygen, 315; combining of water and, by plants, 332-333; releasing of, in baking powder, 349-350; bubbling of, in effervescence, 365-366; in soda water, springs, and baking soda, 366-367; limewater test for, 375-376. Carbonic acid gas, commercial name for pure carbon dioxid, 365-366. Cat's hairs, static electricity in, 201. Caustic soda, a common base, 356. Center of weight, 30-33*. Centrifugal force, 5, 72-74; law of, 74-75. Charcoal, production of, 316. Charging water with carbon dioxid, 366. Chemical analysis, 370-376. Chemical change, and energy, 293 ff.; burning (oxidation), 312-322; caused by heat, 323-325; caused by light, 326-335; caused by electricity, 335-339; energy released by, 340-341; helped by solution, 349-351.