Foot, 29.

Foot pound, 74.
Foot poundal, 74.
Force, defined, 47.
electromotive, 356.
lines of, see Lines.
measurement of, 47.
moment of, 57.
Force pump, 183.

Forced vibrations, 207.
Forces, composition of, 52.

graphical representation of, 52.
parallel, 58-60, 82, 83.
resolution of, 56.
Formulas, 524.
Fountain in vacuo, 167.
F. P. S. system, 28.
Franklin, Benjamin, 342.
Fraunhofer lines, 483.

Freezing mixture, 269.

Freezing point, 240, 268.

Friction, 111.

coefficient of, 111.

electricity produced by, 318, 323,
335.

heat produced by, 247.
Fulcrum, 99.

Fuse wires for electric circuits, 363.
Fusion, 267.

heat of, 283.

g, determination of, 94.
Galileo, 40, 494.

Galton's whistle, 235.

Gauss, 308.

Geissler tubes, 403.

General properties, 14.

Gram, 31.

Graph, 45.

Gravitation, 80.

Gravity, 80.

acceleration of, 40.

center of, 82.

specific, 146-156.

Gravity cell, 350.

Gravity unit, of force, 48.

of work, 74.

Grids, 378.

Gyroscope, 65.

Hardness, 24.

Harmonic motion, 191.
Harmonics, in music, 223.
Harmony, 219.

Hartl optical disk, 444.
Hearing, range of, 235.
Heat, 237-299.

absorption of, 257.

and work, 287–299.
conductors of, 248.

effects of, 238, 259, 267, 269.

expansion caused by, 238, 259–266.
kinetic theory of, 237.

luminous, 258.

measurement of, 281.

mechanical equivalent of, 287.
of fusion, 283.
radiation of, 254.
reflection of, 256.

sources of, 246, 339, 362.
specific, 281.

transmission of, 248.
of vaporization, 284.

wave length, 485.

Heating, electric, 363.

hot water, 251.

Heat lightning, 343.

Heat loss in electric current, 363.

Heat of fusion, 283.

Heat of vaporization, 284.

Heat rays, 485.

Helmholtz resonators, 232.

Hertz waves, 506.

Hoffman's apparatus, 374.

Holtz machine, 335.

Homogeneous atmosphere, 177.

Homogeneous substance, 255.
Hooke's Law, 18.
Horse power, 76.

Hot water heating system, 251.
Humidity, 272.

Hydraulic press, 130.

Hydraulic ram, 139.
Hydrometer, 153.
Hydrostatic press, 130.
Hygrometer, 272.
Hypothesis, 13.

Ice, 266-269.

manufactured, 277.
Ice-pail experiment, 329.
Illumination, intensity of, 439, 502.
Image, defined, 438.

Images, formed by lenses, 470.
formed by mirrors, 445-449.
formed through an opening, 438.
multiple, 447.

real, 453, 454.

virtual, 445, 453, 454.

Impact, heat produced by, 247.
Impenetrability, 14.

Incandescent lighting, 423.
Incidence, angle of, 62, 444, 457.
| Inclination, magnetic, 309.
Inclined plane, 108.

Inclosed arc lamp, 421.
Indestructibility, 16.

Index of refraction, 459.
Induced currents, 328, 393-415.
Induction, electrostatic, 328.
magnetic, 312.

of currents, 328, 393-415.
self-, 399.

Induction coil, 400.

Induction machines, 335.
Inertia, 17.

Initial velocity,

Insulators, 322.

44.

Interference, in light, 486.

in sound, 203.

in wave motion, 203.

Internal resistance, 357, 390.

International prototype standards,

30.

Intervals in music, 215.

Ionization, 517.

Ions, 374.

Isochronous, 94.

Joule's equivalent, 288.

Joly photometer, 441.
Joule, 76.

Kelvin, Lord, 10, 402.

Keynote, 216.

Kilogram, 31.

Kilogrammeter, 74.

Kilowatt, 77, Kilowatt-hour, 391.

Kinetic energy, 71.

Kinetic theory, 11, 157, 237.
Kinetics, 34.

Lactometer, 154.

Lantern, optical, 495.

Law, physical, 13.
Leclanché cell, 351.
Length, unit of, 29.

Lenses, 465-472, 475.

Lenz's law, 412.
Lever, 99.

bent, 101.

compound, 102.

law of the, 100.

Leyden jar, 333, 341, 346.

Lifting jack, 110.
Lifting magnet, 368.

Lifting pump, 182.
Light, 435-505.

defined, 435.

diffused, 443.

dispersion of, 473.

intensity of, 439.
interference, 486.
measurement of, 440.
polarized, 488.
propagation of, 436.

reflection of, 443.

refraction of, 457.

velocity of, 439.

waves, wave length, 474, 484.
Lighting, electric, 420, 502.
Lightning, 343.
Lightning rods, 344.

Lines of magnetic force, 304.

action of, 307, 394.
Liquids, 11, 119–156.
absorption of, 125.
diffusion of, 126.
equilibrium in, 132.
expansion of, 262.

heat conductivity of, 249.
mechanics of, 129–145.

molecular forces in, 119-129.

pressure of, 129–141.

sound transmitted by, 195, 199.

spherical form of, 119.

surface tension, 120.

Liter, 32.

Local action, 348.

Longitudinal vibrations, 192.

Loops, in a sounding body, 222.
Luminous arc, 422.

Luminous bodies, 435.

Luminous heat, 258.

Lycopodium powder, 120.

Machines, 96-118.

general law of, 97.

simple, 98.

Magdeburg hemispheres, 168.

Magnetic declination, 310.

Magnetic drag, 414.

Magnetic effects of electric currents,

364-373.

Magnetic field, 308.

of dynamo, 407.

Magnetic induction, 312.

Magnetic lines of force, 304, 364, 394.

Magnetic meridians, 302.

Magnetic needle, 302.

Magnetic permeability, 306.

Magnetic substances, 301.

Magnetism, 300-317.

explanation of, 314.

of the earth, 308.

Magneto, 404.

Magnets, 300.

distribution of magnetism in, 304.

effect of breaking, 315.

effect of heating, 315.
electro-, 366.

lifting, 368.

mutual action of, 303.
poles of, 302.
Malleability, 24.

Manometer, 179, 241.
Manometric flames, 231.
Marconi, Guglielmo, 507.
Mariotte, Edme, 178.
Mass, 27.

Matter, defined, 10.

kinetic theory of, 11.
properties of, 14-33.
states of, 10,

Maximum current of cells, 360.
Maximum efficiency, 360.
Maxwell, line of force, 308, 366.
Mayer's floating magnets, 304.

Nodes, 222.
Noise, 210.

Normal, 444.