Saros, 426.
Satellites of Jupiter, 511. Of Saturn,
518.547. Nomenclature of, 548. note.
Remarkable relation of periods
among, 550. Discovery of an
eighth, 548. Of Uranus, 523. 552.
Of Neptune, 524. 553. Used to de-
termine masses of their primaries,
532. Obey Kepler's laws, 533.
Eclipses of Jupiter's, 535... Longi-
tude determined by (see Longitude).
Relations among their motions, 542.
Other phænomena of, 540.
dimensions and masses, 540. Dis-
covery, 544. Velocity of light as-
certained from, 545.
Saturn, remarkable deficiency of den-
sity, 508. Rings of, 514.
(See
Rings.) Physical description of,
514. Satellites of, 547. and Appen-
dix. (See also elements in Appen-
dix.)

Their

Schehallien, its attraction measured,
776. e.

Schmidt, his observations of solar
eclipses, 395.

Schubert (Gen.), his determination of
the dimensions and figure of the
earth, 223. a., Note D.

Schwabe, his discovery of periodicity
of solar spots, 394. a. Of excentri-
city of Saturn's rings, 519. note.
Sea, proportion of its depth to radius

of the globe, 31. Its action in mo.
delling the external form of the
earth, 227.

Seasons explained, 362... Tempera-
ture of, 366.
Sector, zenith, 192.

Secular variations, how detected, 385.
Explained, 655...
Selenography, 437.
Sextant, 193...

Shadow, dimensions of the earth's, 422.
428. Cast by Venus, 267. Of Ju-
piter's satellites seen on disc, 540.
Shooting stars, 115. Used for finding
longitudes, 265. Periodical, 900.

(See Meteors.)

394. a.

sons, 394. b.

Spring, proposed use of for determining
variation of gravity, 274.
Standards of length, weight, and ca-
pacity, 223. a., Note D.

Stars, visible by day, 61. Fixed and
erratic, 297. Fixed, 777... Their
apparent magnitudes, 778... Com-
parison by an astrometer, 783. Law
of distribution over heavens, 785...
alike in either hemisphere, 794.
Parallax of certain, 815. Discs of,

816. Real size and absolute light,
817. Periodical, 820... Temporary,
827. Irregular, 830. Missing, 832.
Double, 833... Coloured, 851, and
note. Proper motions of, 852. Ir-
regularities in motions accounted
for, 859. Clusters of, 864... Ne-
bulous, 879... Nebulous-double,
880.

Stationary points of planets, 459. How
determined, 475. Of Mercury and
Venus, 476.

Stereograms of the moon, 430. a., Note
H.

Stereographic projection, 281.

Sticklastad, eclipse of, 926. and Table,

horizon explained, 47. Apparent
motion not uniform, 34. Beams
converging, 115. Orbit elliptic, 349.
Greatest and least apparent diame-
ters, 348. Actual distance, 357.
Overrated, its probable correction,
357. a., Note F. Magnitude, 358.
Rotation on axis, 359, 360. Mass,
449. Physical constitution, 386.
Spots, ib... Its parallax, 355. Light,
not polarized, 387. note. Its inte-
rior envelope, 389. a. Its pores, 387,
387. a., Note G. Willow-leaved
structure of its photosphere, ib. Fa-
culæ, 388. Situation of its equator,
390... Maculiferous zones of, 393.
Atmosphere, 395. Its rose-coloured
clouds, 395. Relative illumination
of center and borders, 386... 395.
Temperature, 396. Expenditure of
heat, 397. Action in producing
winds, &c. 399. Speculation on
cause of its heat, 400. and note, 905.
a, b. Eclipses, 420. Density of, 449.
Natural center of planetary system,
462. Distance, how determined, 479.
Its size illustrated, 526. Action in
producing tides, 751. Proper motion
of, 854... 858, a, b, c, Note L.
Absolute velocity of, in space, 858.
Central, speculations on, 861.
Sunsets, two witnessed in one day,

Tides, a system of forced oscillations,
651. Explained, 750... Priming
and lagging of, 753. Periodical in-
equalities of, 755. Instances of very
high, 756.

Time, sidereal, 110. 327. 911. Local,
129. 152. 252. Sidereal and solar,
243. Mean and apparent sidereal,
327. Measures angular motion,
149. How itself measured, 150...
Very small intervals of, 150. Equi-
noctial, 257. 925... Measures, units,
and reckoning of, 906... Required
for light of stars to reach the earth,
802.

Venus, synodic revolution of, 472. Sta-
tionary points, 476. Velocity of, 474.
Phases, 477. Point of greatest
brightness, 478. Transits of, 479.
Physical description and appear-
ance, 509. Inequality in earth's
motion produced by, 726. In that
of the moon, 743...
Vernier, 97.

Vertical, prime, 102. Circles, 100.
Vesta, discovery of, 505.
Via Lactea. (See Galaxy.)

Villarceaux (M. Yvon), his orbits of
double stars, 843.
Volcanos, lunar, 430. a., Note H.

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