7, 271; velocity of, i. 412;
nterference of, 176; classi-
,423.

376; infima, 380; natural,

at of air, ii. 197.

i. 329, 348; ii. 9, 97, 229,
homas Melvill on, 38.

Herbert, laws of thought, i.
1 of equality, 18; rhythmical
1, ii. 61; abstraction and gene-
on, 390; theories of, 405;
fication of predicate, 387.
eous generation, ii. 43.
is, i. 365.

motion of, i. 325, 348; ii. 93,
15; variable, i. 326; ii. 64, 358;
i. 464; coloured, ii. 358; heat
430; conflict with, 443.
us, ii. 276.

rt, Balfour, sun-spots, ii. 67;
ereal friction, 213.

i. 206.

s, on resistance, ii. 96; fluor-
ence, 332.

e, E. J., radiant heat of stars, i.
30; temperature periods, ii. 67;
ansit of Venus, 204.

itt, J. W., graphical method, ii.
19.

bstantial terms, i. 34.

bstitution of similars, i. 21, 25; ii.
345; of weights, i. 23, 399.
ni generis, ii. 286, 418.
'ulphur, 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, i. 36; of laws, 140.
Syren, i. 12, 348; ii. 28.

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, 110.
Variation, instance of, i. 324; method
of, ii. 50; periodic, 61; combined