on, 287
on electricity, 332
on induction, 176

Faye, M., 111, 302, 319

Faye's comet, 293, 296

Field, electric, 179
magnetic, 199

Fizeau, 149, 224

Fluids, 48

Food, 89

Forbes, 121

Force, 16, 19, 90
centrifugal, 9, 13, 236
centripetal, 9, 12, 282
lines of, 200

Forces, direction of the, 26
proportion of the, 26

Foucault, 149

Franklin, 106

Fresnel, 75, 131

Frictionless medium, 17, 131, 136, 224

Fundamental medium, 54

Galaxy, 325, 346

Gaseous nebulae, 313

Gases, condensation of, 47
liquefaction of, 47
kinetic theory of, 49

Glazebrook, Prof., on aether and gravitation, 22

Globular clusters of stars, 314

Gravitation, law of, 61, 65
universal, 24
intensity of, 27
law of proportion, 26
cause of, 1, 282
and binary stars, 25

Gravity, centre of, 325

Great Bear, 307

Grove, 83

Halley's comet, 296-7

Hamilton, Sir W. R., 247

Head of comets, 298

Heat is motion, 98
a mode of motion, 107
radiant, 109
dynamical equivalent of, 116
effects of, 107
nature of, 98
radiation of, 109
transformation of, 87

Heat engine, Carnot's, 116
of sun, 109
and matter, 100
and work, 114
refraction of, 121

Helmholtz, Von, 45, 86

Hercules, 257, 271, 307

Herschel, Sir J., 3, 4, 7, 226, 228, 281, 299, 301, 310, 321
Sir W., 109, 271-2, 313

Hertz, 138, 159, 182

Hicks, Prof., 13

Hodograph of planets, 247

Hot springs, 90

Huggins, 313-14

Huyghens, 54, 123, 125, 128

Hydrogen, 40, 42, 44, 60, 93, 314, 333

Hypotheses, 3, 338

Ice, 42

Identity of heat and light, 119
light and electricity, 156, 160, 165
aether and electricity, 331

Imponderable, 71

Impressed force, 20

Impressible aether, 78

Induction, electric, 174-5
magnetic, 199
Faraday's theory of, 175

Inertia of matter, 52
of aether, 330

Intensity of light, 28, 146
of heat, 28, 113
of electricity, 184
of gravity, 28

Iron, 42
expansion by heat, 101
contraction by cold, 102

Joule, 85, 114

Jupiter, 26, 68
mass of, 235
satellites of, 149, 178
rotation of, 219
orbital velocity of, 251, 265
size of, 235
distance from sun, 242, 251
density of, 242
and comets, 305

Kant, 317

Kelvin, Lord, 43, 71, 77, 80, 95, 216, 227
on aether, 56-7
on vortex atom, 63
on compressible aether, 291, 315
on light, 151

Kepler's laws, 32
first, 33, 256-9
second, 36, 260-2
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