7*-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.

Electric lamps, vacuums in, 12*, 317;
incandescent, 125;
gas-filled, 317.

Electric motors, 256*-257*.

Electrolysis apparatus, 294-295*.

Electromagnets, 247-257*.

Electrons, 193;
description of, 197;
number of, in negative and in positive charges, 198-200.

Elements, defined, 293;
chemists' abbreviations of, 297-299;
list of common, 299-300;
hiding of, in compounds, 300-301.

Emulsion, defined, 261;
difference between solution and, 263.

Energy released by chemical change, 340-341.

Engine, working of cylinder and piston of, 344*.

Ether, carrying of heat and light by, 124-125;
light as waves of, 163-164.

Ether waves, 124-125, 163-164.

Evaporating dish, 101*.

Evaporation, 100-106*;
part taken by, in formation of clouds, rain, and dew, 277.

Expansion, caused by heat, 88-93;
cooling from, 94-96*.

Expansion ball and ring experiment, 91*-92.

Explosions, use of, 342* ff.;
automobiles made to go by succession of, 344-345;
cause of, 345;
shooting of guns caused by, 345-346.

Explosives, manufacture of, 347.

Extension lights, 238.

Eye, lens of, 142;
section of, 151*;
working of, 151*-153.

Fading, process of, 326-327.

Filament of incandescent lamp, 125.

Fire engines, need of, to force water high, 9.

Fire extinguishers, action of, 317.

Fires, caused by electric arcs, 236;
putting out of, by water, 317.
_See_ Burning.

Flames, formation of, 318.

Floating, sinking and, 23-28.

Focus of light, 142*-149*.

Fogs, cause of, 288.

F