Chemical equations, 297-299. Chlorine, an element, 299. Chlorophyll in plants, work of, 332. Cigar-box telegraph, construction of, 249*, 380-381*. Circuits, electric, 219-220*; breaking and making, 220-221; connecting in parallel, 221-223*; grounded, 225-229*; short, 240-245*. Cloth, action of acids on, 354*; action of an alkali on, 356, 357*. Clouds, how formed, 277-278. Coal, carbon and hydrogen in, 315. Cohesion, 39, 44*-49. Cold, caused by expansion, 94; is the absence of heat, 95, 120. Color, 161-172*. Comb, electricity produced by rubbing, 197-198. Compass, use of, 190-195*. Complete electric circuits, 219-224*. Compounds, how elements hide in, 300; definition of, 308-309; mixtures distinguished from, 309-310. Concave mirrors, 154*, 155*, 157; magnification by, 157; in reflecting telescopes, 157. Conduction, of heat, 116-118; of electricity, 213-218. Conductors of electricity, good and poor, 213. Conduits for electric wires, 237. Conservation of energy, 57 ff. Convection, carrying of heat by, 118-119. Convex lens, 148-149*; in microscope, 155-157*; in telescope, 157. Cooling from expansion, 94-96. Coolness at night and in winter, 127-128. Copper, a good conductor of electricity, 215; an element, 299; nickel plating of, 336-339*; etching of, with acid, 352*-353. Copper nitrate, salt called, 353. Cream, separating from milk, by centrifugal force, 75-76. Crystals, formation of, 265-268. Cylinder of engine, 344*. Dead Sea, reason for salt in, 104-105*. Decay, a kind of oxidation, 313. Dew, 275; how formed, 287. Dictaphone, working of, 175, 178, 179*. Diffusion, 268-274; of light, 158-161. Direct-current electricity, 211-212. Distilling of liquids, 112-115*. Doorbell, electric battery for ringing, 204-205. "Down," meaning of word, 4. Drainpipe, cleaning of, with lye, 358. Dry-cell battery, 206*. Dust, reason for clinging to walls, 43-44. Dynamite, 343*; making of, 347. Dynamo, how electric current is made to flow by, 207*-210*. Earth, magnetism of, 190-195. Easy circuit, a short circuit an, 244-245. Echoes, explanation of, 183-185. Effervescence, process of, 365; generally due to freeing of carbon dioxid, 367*-368; helped by stirring or shaking, 368. Elasticity, 82-86; of form distinguished from elasticity of volume, 86-87. Electrical apparatus, 216-217*, 222-223*; description of, 379-380. Electric arc, the, 233*-240. Electric battery, the, 203-206*. Electricity, magnetism and, 190 ff.; static, 196-202; negative and positive charges of, 198*-200; action of, in thunderstorms, 200-201; flowing, 203 ff.; flowing of, in dynamo, 207-210; alternating and direct-current, 211-212; conduction of, 213*-218; chemical change caused by, 335-339.