cal 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.

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, 20