Endosmose, 82

Energy, of vibrations, 122; definition
of, 97, 98; relations between, and
momentum, 99; is of two types,
IOI; varieties of, 102; visible, 104;
invisible, 104; conservation of, 107;
not annihilated when a stone
thrown vertically upwards, 107; not
destroyed by impact, 108; converted
into heat by impact, 109; the quan-
tity of, remains always the same,
III; of rctat.on, 117; of a body
moving in an ellipse, 118; of a body
falling down a plane, 119; of a pen-
dulum, 119; dissipation of, 373;
sources of, 375; the various trans-
mutations of, 378
Eolipyle, the, 36, 221

Equilibrium, stable, 53; unstable, 53
Ether, compression of, 71

Evaporation, 183; change of composi-
tion in, 189
Exosmose, 82

Expansion, linear, 166; co-efficient of,
167; cubical, 168

Expansion of liquids, 170, 174; appa-

rent, 170; real, 170; of mercury,
172; of water, 172; of gases, 174;
applications of the laws of, 176
Eye, the, 253

Galvanic circuit, 110
Galvanometer, 342

Gas, the diffusin of, 96; the absorp-
tion of, by solids and liquids, 96
Gaseous state of matter, 4
Gases, forces exhibited in, 82; velc-

city of scund in various, 137; con-
ductivity of, 199; the spectra of,
269; specific heat of, 205; compres-
sion of, 216

Gases and vapours, density of, 138,

191

Gassiot, 368

Gay-Lussac, 191

Gilbert, Dr., 298

Girgenti, the cathedral of, 135
Graham, the late Mr., 96

Graduation of thermometers, 161
Gravitation, 5; variation of, 40; the
grand law of, 43

Gravity, the effect of, in increasing
the velocity of a falling body, 18;
space passed over by a falling body
under the action of, 18; oblique
motion under, 24; terrestrial, 38;
the force of, measured by the oscil-
lation of a pendulum, 39; the force
of, always proportional to the mass,
40; the directions in which the force
of, acts, not really parallel to one
another, 40; recapitulation of facis
connected with the action of, at the
earth's surface, 51; centre of, 51;
specific, 79

Grotthuss, 364

Grove's battery, 339.

Gun, recoil in the firing of a, 33
Guthrie, Prof., 199

H.

Hardness, 65; scale of, 65
Heat, a motion of particles, 103; la-
tent, 104, 207; radiant, 105; me-
chanical equivalent of, 109; bodies
in general expand through, 158;
change of state, and other effects of,
180; effect of, upon refraction, 193;
upon dispersion, 193; upon capil-
larity, 193; specific, 203; twofold
office of, as a species of molecular
energy, 212; conversion of mechani-
cal energy into, 215; conversion of,
into work, 218; effect of upon mag-
nets, 330; mechanical energy con-
verted into, 352; electricity in motion
converted into, 360; the quantity of,
given out by chemical combination,
372; the quantity of, developed by
the mutual action of metals, 373
Heat energies, 104

Heat-engines, proportion of heat which
may be utilised in, 220; history of,

L.

Lake, freezing of a, 201
Land-breeze, 203
Langley, S. P., 369

Latent heat, 207; of liquids, 208; of
vapours, 209

Length, unit of, 7; standards of, 177
Lenses, 248; images formed by, 251
Leslie, Sir John, 214, 265
Leyden jar, the, 316
Lifting-pump, 93

Light, radiant, 105; rays of, 225; un-
dulatory theory of, 226; reflection
of, 226; velocity of, 227; intensity
of, 228; refraction of, 226, 241;
electric, 362

Lighting, electric, 370

Linear compression, resistance to, 59;
force resisting, 67

Linear expansion, 166; of some of the
more important solids, 167

Linear extension, resistance to, 59;
force resisting, 66
Linear velocity, 114
Liquefaction, 181

Liquid state of matter, 4

Liquids, forces exhibited in, 70; cohe-
sion of, very small, 70; offer great
resistance to forces tending to com-
press them into smaller volume, 71;
not incompressible, 71; pressure of,
proportional to their density, 76;
velocity of sound in, 139; laws for
the expansion of, 174; conductivity
of, 203; expansion of, 170; table of
thermal resistance of, 199; specific
heat of, 205; latent heat of, 208
Lissajous, 155
Lockyer, 279, 292
Longitudinal vibrations, 148
Luminosity, intrinsic, 229

M.

Machine, the function of a, III
Magnet, 324; properties of a, 324;
poles of the, 325; the marked pole
of the, 325; the effect of breaking a,
328; the earth acts as a, 330; effect
of the electric current upon a, 341
Magnetic bodies, 325; induction, 328
Magneto-electrical machines, 352
Magnets, action of, upon each other,
327; how to make, 329; the effect
of heat upon, 330; made to play
the part of currents, 351
Malleability, 64

Mass, unit of, 9; how estimated, 11;
correctly represented by weight, 11,
40; standards of, 177

Matter, various aggregations of, 2;
three states of, 4

Microphone, 368

Microscope, the simple, 254
Milky way, or galaxy, 2

Mirage, the, 245

Mirrors, plane, 232; curved, 234;

parabolic, 240; convex, 241
Molecular forces, 37

Molecular separation, 104
Molecule, a, 3

Moment of a force, 32

Momentum, 26; relation between and
energy, 99

Moon, force of the earth's attraction
at the, 42

Motion, the relative character of, 4;
can be produced or destroyed only
by force, 5; the first law of, 12; an
extension of the first law of, 115;
the second law of, 14; the third law
of, 33; energy of, or kinetic energy,
102, 103; electricity in, 106
Motions, oscillatory, 119

Moving bodies, the action of a single
force on a, 14; the action of two or
more forces on a, 25
Musical sound, 132

N.

Newton, 38, 39, 41, 255
Newton's rings, 288

Newtonian theory of light, 282

Nodal lines, 150; points, 151
Noise, 132

Parabolic mirrors, 240;
from, 240

Parallel forces, 31

reflection

Parallelogram of forces, 26; as a pro-
position in statics, 30

Pascal, 71; his experiments, 87
Pencil of rays, divergent, 226; par-
allel, 226; convergent, 226

Pendulum, the, 39; the bob of a, 39 ;
a means of measuring the force of
gravity, 39, 57; energy of, 119
Perpetual motion, 107, 111, 373
Person, 209

Petit, 206

Phase of a vibrating particle, the, 130
Phosphorescence, 281

Photometer, 230

Physics, definition of, r
Pierre, 174

Plane, energy of a body falling down

pencil of, 226; dispersion of, 256:
surfaces or plates do not behave in
the same manner with regard to dif-
ferent kinds of, 273; bodies when
cold absorb the same kind of, that
they give out when heated, 274
Reflection, 226; total internal, 244;
polarization by, 294

Reflection of light from plane mirrors,
232: from curved mirrors, 234; from
parabolic mirrors, 240; from convex
mirrors, 241

Reflectors, conjugate, 135,
Refraction, 226; of sound, 136; effect
of heat upon, 193; of light, 241;
index of, 243
Regelation, 182

Regnault, 172, 190, 192, 205, 206, 209
Retina, the, 253

Rifle ball, the energy of a, 114

Rods, vibrations of, 148; time of
vibratory motion of, 148

Römer, 227

Roscoe, 267

Rotation, phenomena of. explained by
the first law of motion, 14; energy
of, 117

Ruhmkorff's coil, 353
Rumford, 109

Sea-breeze, 203

Seebeck, 260

S.

Self-registering minimum thermome-

ters, 165; maximum, 165

Sight, short, 254; lɔng, 255

Solenoids, 348

Solid state of matter, 4

Solid, the essential character of a, 70
Solidification, 182

Solids, forces exhibited in, 58; with-
out structure, 62; cohesion in, 62;
velocity of sound in, 139; expansion
of, 166; remarks on, 169; specific
heat of, 204; conduction in, 195
Solids and liquids, table of the specific
gravities of some of the most import-
ant, 80

Sondhauss, 137

Sound, reflection of, 134; refraction
of, 136; velocity of, in air, 137;
mode of determining, 154; in various
gases, 137; circumstances affecting
intensity of, 140; the intensity of
the, depends upon density of the
air, 140; the propagation of, favoured
by the calmness and homogeneity of

Tait, Professor, 359

Tangent compass, 344
Telephone, 366
Telescope, the, 254
Temper, 65

Temperature, 157; measurement of,
by thermometer, 158; velocity of
sound varies with. 139; the varia-
tion of volume with, 175
Tempering, 65
Tenacity, 62

Terrestrial gravity, 40
Thermo-electric currents, 339
Thermometers, measurement of tem-
perature by, 158; mercurial, 159;
determination of fixed points of, 160;
graduation of, 161; corrections to
mercurial, 163; self-registering mini-
mum, 165; maximum, 165; differen-
tial, 165; air, 176

Thermo-pile, the, 260

Thin-plates, colours of, 287

Thomson, Sir William, 220, 313, 335, 374

Vibration, time of, 125; in strings,
144; in rods, 148; of air in organ-
pipes, 152
Vibrations, energy of, 122; of strings,
143; of rods, 148; transverse, 148;
longitudinal, 148; cf plates, 152;
the communication of, 153; the
determination of number of, 153;
graphical representations of, 155
Virtual image, 232
Viscous fluids, 70

Vis.ble energy, 104; varieties of, 103;
of position, 119,

Volta, 332; his pile, 332; his explana-
tion of the effect produced by the
voltaic battery, 334

Voltaic batteries, 332; distribution and
movement of electricity in, 354
Volume, the variation of, with tem-
perature, 175

W.

Water, compression of, 71; table ex-
hibiting the volume of, at various
temperatures, 173; remarks on latent
heat of, 210; the vapour of, 210;
expansion cf, 172
Water-level, 74

Watt, James, his improvements on
Newcomen's engine, 222

Wave, the front of a, 283
Wave-length, a, 128
Wave-motion, 128

Waves, up and down, 128; of con-
densation and rarefaction, 130
Weber, Dr. H. F., 205, 207.

Weight, a correct representation of
mass, 11, 39

Wheatstone, Sir C., 310, 336
Wind instruments, 147

Wind, its effect on the audibility of
sound, 141

Winds, trade, 202; anti-trade, 202
Work, 98; unit of, 98; conversion of
heat into, 218

Y.

Young, 294