used with the aid of such maps as the present. They revolve round the pole once in twenty-four hours (less about four minutes), in a direction contrary to that of a clock's hands. But stars near the equator, whose motions are much more rapid, afford a yet better measure of time, if the direction of the south point is well determined.

Of course, the observer who really wishes to become an astronomer will not rest satisfied by learning only the principal stars shown in these maps. By means of the regular star-maps, such as those of my School Star Atlas, he will be able to explore the depths of all the constellations, having once learned their position and general appearance from the accompanying maps. It will be well for the student to remember that the planets Venus, Mars, Jupiter, and Saturn will at times appear among the constellations here shown. Venus and Jupiter can always be recognized by their superior light, Mars and Saturn by the steadiness with which they shine. The almanac will always show when these planets and Mercury (often very bright in the clear skies of America) are above the horizon, and where they are situate. They never appear except among the zodiacal constellations.

For particulars and pictures of the different constellations, and other details associated with the study of the star-groupings, the reader is referred to my "Easy Star Lessons," published like the present maps by Messrs. Putnam's Sons. I have to thank the proprietors of the Scientific American for permission to publish these maps, which originally appeared (though in a slightly different form) in the pages of that excellent magazine. The Latin names of the constellations included in the maps of this series are as follows:

THE LITTLE BEAR, Ursa Minor (α, the Pole Star; β, γ, the Guardians).
THE DRAGON, Draco (α, Thuban).
KING CEPHEUS, Cepheus.
THE LADY IN THE CHAIR, Cassiopeia.
THE CHAMPION, Perseus (β, Algol, remarkable variable).
THE CHARIOTEER, Auriga (α, Capella).
THE GREATER BEAR, Ursa Major (α, β, the Pointers).
THE HUNTING DOGS, Canes venatici (α, Cor Caroli).
QUEEN BERENICE'S HAIR, Coma Berenices.
THE HERDSMAN, Boötes (α, Arcturus).
THE NORTHERN CROWN, Corona Borealis.
THE SERPENT, Serpens.
THE KNEELER, Hercules.
THE LYRE, Lyra (α, Vega).
THE SWAN, Cygnus (α, Arided; β, Albireo).
THE WINGED HORSE, Pegasus.
THE CHAINED LADY, Andromeda.
THE TRIANGLES, Triangula.
THE RAM, Aries.
THE BULL, Taurus (α, Aldebaran; η, Alcyone, the chief Pleiad).
THE TWINS, Gemini (α, Castor; β, Pollux).
THE CRAB, Cancer (the cluster between γ and δ is the Beehive).
THE LION, Leo(α, Regulus).
THE VIRGIN, Virgo (α, Spica).
THE SCALES, Libra.
THE SERPENT-HOLDER, Ophiuchus.
THE EAGLE, Aquila (α, Altair).
THE DOLPHIN, Delphinus.
THE WATER CARRIER, Aquarius.
THE FISHES, Pisces.
THE SEA MONSTER, Cetus (ο, Mira, remarkable variable)
THE RIVER, Eridanus.
THE GIANT HUNTER, Orion (α, Betelgeux; β, Rigel).
THE LESSER DOG, Canis Minor (α, Procyon).
THE SEA SERPENT, Hydra (α, Alphard).
THE CUP, Crater (α, Alkes).
THE CROW, Corvus.
THE SCORPION, Scorpio (α, Antares).
THE ARCHER, Sagittarius.
THE SEA-GOAT, Capricornus.
THE SOUTHERN FISH, Piscis Australis (α, Fomalhaut).
THE HARE, Lepus.
THE DOVE, Columba.
THE GREATER DOG, Canis Major, (α, Sirius).
THE SHIP, Argo.
THE CENTAUR, Centaurus.

The following table exhibits the names of all the stars of the first three magnitudes to which astronomers have given names; at least, all those whose names are in common use: