TABLE OF USEFUL ASTRONOMICAL FACTS.

The sun’s mean distance from the earth is 92,700,000 miles; his diameter is 865,000 miles, and he rotates in a period between 25 and 26 days.

The moon’s mean distance from the earth is 238,000 miles; the diameter of the moon is 2160 miles, and the time of revolution round the earth is 27.322 days.

THE PLANETS.

   Mean Distance
from the Sun
in Millions
of Miles.		 Periodic Time
of Revolution
in Days.		 Diameter
of Planet
in Miles.		 Axial Rotation.
            Hrs. Mins. Secs.
Mercury      35.9        87.969   2,992 Uncertain.
Venus      67.0      224.70     7,660 Uncertain.
Earth      92.7      365.26     7,918 23 56   4.09
Mars    141         686.98     4,200 24 37 22.7  
Jupiter    482      4,332.6     85,000   9 55 —
Saturn    884    10,759        71,000 10 14 23.8  
Uranus 1,780    30,687        31,700 Unknown.
Neptune 2,780    60,127        34,500 Unknown.

THE SATELLITES OF MARS.

Name. Mean Distance from
Centre of Mars.		 Periodic Time.
    Hrs. Mins. Secs.
Phobos   5,800 miles.   7 39 14
Deimos 14,500   ”      30 17 54

THE SATELLITES OF JUPITER.

Name. Mean Distance from
Centre of Jupiter.		 Periodic Time.
    Days Hrs. Mins. Secs.
I    262,000 miles.   1 18 27 34
II    417,000   ”        3 13 13 42
III    664,000   ”        7   3 42 33
IV 1,170,000   ”      16 16 32 11
V    112,400   ”      — 11 57 (?)

THE SATELLITES OF SATURN.

Name. Mean Distance from
Centre of Saturn.		 Periodic Time.
    Days Hrs. Mins. Secs.
Mimas    118,000 miles.   0 22 37 27.9
Enceladus    152,000   ”        1   8 53   6.7
Tethys    188,000   ”        1 21 18 25.7
Dione    241,000   ”        2 17 41   8.9
Rhea    337,000   ”        4 12 25 10.8
Titan    781,000   ”      15 22 41 25.2
Hyperion    946,000   ”      21   7   7 40.8
Iapetus 2,280,000   ”      79   7 54 40.4

A ninth satellite was discovered in August, 1898, by Prof. W. H. Pickering, but its mean distance and periodic time have not yet been determined with precision.

THE SATELLITES OF URANUS.

Name. Mean Distance from
Centre of Uranus.		 Periodic Time.
Days.
Ariel 119,000 miles.   2.520383
Umbriel 166,000   ”        4.144121
Titania 272,000   ”        8.705897
Oberon 363,000   ”      13.463269

THE SATELLITE OF NEPTUNE.

Name. Mean Distance from
Centre of Neptune.		 Periodic Time.
Days.
Anonymous 220,000 miles. 5.87690