Prime numbers, i. 141, 265.
Principia, ii. 227.

Principle, of probability, i. 228; of
inverse method, 279; of forced vibra-
tions, ii. 65, 332; of coexistence of
small vibrations, 97; of super-position
of small effects, 98.
Probability, meaning of, i. 224; princi-
ples of, 228; rules of, 231; com-
parison with experience, 238; diffi-
culties of theory, 243; inductive
application of, 276; inverse method
of, 279; ii. 244; application to
astronomy, i. 285; inverse problem,
289; general solution, 295; rules of
inverse method, 297; works on, 459.
Probable error, i. 451; ii. 194.
Proclus, commentaries of, i. 267.
Proctor, R. A., on star drifts, i. 287.
Projectiles, theory of, ii. 85.
Properties, generality of, ii. 249; uni.
form, 254; variable, 258; extreme,
259; correlation of, 353.

Property, logical, ii. 377; peculiar,
377.

Propositions, i. 43; negative, 52; con-
version of, 55; twofold interpretation
of, 57; disjunctive, 89; equivalency
of, 132.

Protean verses, i. 197.
Protoplasm, ii. 155.

Prout, law of, i. 304; ii. 82.

Pythagoras, on duality, i. 110; on
number seven, ii. 279.

Q.

Quadric variations, ii. 95.

Quantification of predicate, i. 49; ii.
387.

Quantity, continuous, i. 318; ii. 108;
of revolution, i. 358.

Quartz crystals, i. 367; ii. 261, 287.
Quaternions, i. 180; ii. 457.
Quetelet, on average, i. 214; experi-
ments on probability, 237; use of
mean, 421; law of error, 441; ii.
321; errors of observation, i. 446;
letters on probability, 459.

Regnault, dilatation of mercury, i.
396; measurement of heat, 405;
dilatation of gases, 462; ii. 87
latent heat of steam, 111; graphical
method, 118; specific heat of air, 197.
Regular system of crystals, ii. 360.
Reign of law, ii. 428.

Rejection of observations, i. 456.
Relation, sign of, i. 20; logic of, 27.
Repetition, method of, i. 335, 336, 353-
Representative hypotheses, ii. 156.
Residual phenomena, ii. 199, 201.
Resisting medium, i. 363; ii. 155, 213.
Retrograde motion, ii. 327.
Reversal, method of, i. 410.
Revolution, quantity of, i. 358.
Robison, electric curves, ii. 58.
Rock-salt, ii. 40, 261.

Roemer, divided circle, i. 411; velocity
of light, ii. 169.

Roscoe, chemical action of light, i.

316; experiments on solubility, 325;
standard unit of light, 378; ii. 52;
researches on vanadium, i. 457; ii.
312; absorption of gases, 125.
Rotation of plane of polarized light, ii.
318.

Rousseau on geometry, i. 268.

Rules, for calculation of combinations,
i. 204; of probabilities, 231; of in-
verse method, 297; for elimination
of error, 409.

Rumford, i. 397, 405; ii. 86.
Ruminant animals, ii. 356, 391.

S.

Sandeman, perigon, i. 358; approximate
arithmetic, ii. 104.

Saturn, satellite of, i. 341; rings of,
ii. 319.

Secular variations, ii. 61.
Selenium, ii. 330, 341.

Seven, fallacies concerning number, i.
303; ii. 279.

Sidereal day, i. 337, 362.

Simple identity, i. 44; inference with,
61; contrapositive of, 101; induction
of, 146.

Simplicity, law of, i. 39, 85, 87, 181;
axiom of, ii, 280.
Slate, logical, i. 110.

Smeaton, experiments on friction, i.

402; on windmills, ii. 4, 52.

Smee, Alfred, logical machines, i. 124.
Smell, sense of, ii. 47, 424.

Socrates, error of, ii. 263; on kind, 406.
Sodium-light, ii. 39, 47, 261.

Solar day, i. 337, 355; system, ii. 356.
Solids, ii. 252.

Specific heat of air, ii. 197.

Spectrum, i. 329, 348; ii. 9, 97, 229,
251; Thomas Melvill on, 38.
Spencer, Herbert, laws of thought, i.
9; sign of equality, 18; rhythmical
motion, ii. 61; abstraction and gene-
ralization, 390; theories of, 405;
quantification of predicate, 387.
Spontaneous generation, ii. 43.
Standards, i. 365.

Stars, motion of, i. 325, 348; ii. 93,
95, 215; variable, i. 326; ii. 64, 358;
discs, i. 464; coloured, ii. 358; heat
of, i. 430; conflict with, 443.
Stevinus, ii. 276.

Stewart, Balfour, sun-spots, ii. 67;
ethereal friction, 213.

Stifels, i. 206.

Stokes, on resistance, ii. 96; fluor-
escence, 332.

Stone, E. J., radiant heat of stars, i.

430; temperature periods, ii. 67;
transit of Venus, 204.

Strutt, J. W., graphical method, ii.

119.

Substantial terms, i. 34.

Substitution of similars, i. 21, 25; ii.
345; of weights, i. 23, 399.
Sui generis, ii. 286, 418.
Sulphur, ii. 341.

Summum genus, i. 108; ii. 379.
Sun, distance, ii. 204.

Swan, W., sodium light, ii. 39.
Syllogism, Barbara, i. 66, 103, 121;
Celarent, 67; Darii, Ferio, 67, 68;
Darapti, 71; Camestres, Cesare, 99;
Baroko, Bocardo, 100; disjunctive,
92.
Symbols, logical, i. 39.
Synthesis, of terms,
Syren, i. 12, 348; ii. 28.

36; of laws, 140.

Tautologous propositions, i. 138.

Teeth, as criteria of classification, ii.
395.

Temperature, ii. 68.

Terms, i. 29; substantial, 24; collec-
tive, 35; synthesis of, 36; abstract,
38; logical and numerical, 180.
Test experiments, i. 402.

Tetractys,

Thales, ii. 171.

479

Theory, results of, ii. 168; facts known
by, 185; quantitative, 189, 192; dis-
cordance of, 198.

Thermometer, differential, i. 400; read-
ing of, 404; change of zero, 455.
Thermopile, i. 348.

Thomson, James, ii. 178.
Thomson, Sir W., size of atoms, i. 222;
tides, ii. 64; thermal phenomena,
180, 197; capillary attraction, 267;
magnetism, 333; heat-history of uni-
verse, 438.

Thomson and Tait, chronometry, i. 364;
problem of bars, ii. 77; polarised
light, 318.

Tide-guage, i. 427.

Tides, ii. 64, 66, 98, 178, 195; atmo-
spheric, i. 425, 426; ii. 192.

Time, measurement of, i. 359; equal
times, 362.

Todhunter, on Michell's speculations, i.
286; his History, 460.

Torricelli, ii. 336; theorem of, 67, 256.
Torsion-balance, i. 354; ii. 78.

Transit, instrument, i. 411; of Venus,
i. 343, 399; ii. 202.

Tree of Porphyry, ii. 381.

Triangle, arithmetical, i. 108, 439, 444;
of forces, ii. 292.

Triangular numbers, i. 209.
Trigonometrical survey, i. 351; ii. 453.
Tycho Brahe, on star discs, i. 314, 321;
obliquity of earth's axis, 337; cir-
cumpolar stars, 425; Sirius, 454.
Tyndall, natural constants, i. 380;
precautions in experiment, ii. 41;
singing flames, 109; use of hypo-
thesis, 134; magnetism, 188; scope
for discovery, 499.

Types, classification by, ii. 409, 411.

U.

Undistributed middle, i. 77.
Undulations, ii. 176, 293, 423.
Undulatory theory, ii. 150, 174, 315,
337.

Uniformity of nature, ii. 440.
Unit, definition of, i. 176; of time, 359;
of space, 365; of density, 371; of
mass, 372; subsidiary, 374; derived,
375; provisionally independent, 377.
Unity, law of, i. 86, 176, 182.

V.

Vapour-densities, ii. 186; anomalous,

339.

Variable, variant, ii. 51, 11O.
Variation, instance of, i. 324; method
of, ii. 50; periodic, 61; combined

periodic, 63; integrated, 67; elliptic,
94; simple proportional, 127.
Vegetables and animals, ii. 396.
Vertebrata, ii. 373.

Vibrations, isochronous, i. 344; prin-
ciple of forced, ii. 65; analogy to
nerve influence, ii. 287.

Vital force, ii. 155.

Voltaire, ii. 327.

Vortices, theory of, ii. 142, 146.

W.

Wallis, i. 143; parallax of stars, 393.
Water, properties of, ii. 261.
Watts' parallel motion, ii. 79.

Waves, ii. 155, 333; experiments on,

i. 340; theory of, ii. 170, 248.
Weighted observations, i. 449.
Wells, on dew, ii. 34.

Wenzel, on neutral salts, i. 344.
Wheatstone, i. 143; ii. 53; galvano-
meter, i. 333; rotating mirror, 349;
electric sparks, 360; kaleidophone,
ii. 58.

Whewell, on tides, i. 432; ii. 178;
method of least squares, i. 448.

Whitworth, Sir. J., system of screws, i.
25; measurement of length, 356; ii.
47.
Wilbraham, on Boole's method, i. 235-
Williamson. A. W., on subsidiary units,
i. 374; prediction in organic chem-
istry, ii. 181.
Wollaston, goniometer, i. 334; sun-
light, 352; spectrum, ii. 38.

X.

X, the substance, ii. 155.

Y.

Yard, standard, i. 463.

Young, on Diodorus Siculus, i. 284;
connexion of languages, 285; tension
of aqueous vapour, ii. 126; use of
hypothesis, 136; ethereal medium,
145.

Z.

Zodiacal light, i. 321.
Zoology, ii. 335.