The most interesting feature about Jupiter for the amateur astronomer consists in observing four of its moons, which are visible with a small telescope. They appear like mere dots of light, and their transit of or occultation with the planet (that is, their disappearance before or behind its disk) can be watched, and is a never failing source of pleasure. A large telescope alone reveals Jupiter's four other moons. SATURN. Saturn is farther removed from the earth than any of the planets in the solar system, visible to the naked eye. It is distinguished from the fixed stars by the steadiness of its light, which is dull and of a yellow hue, though to some it appears to be of a greenish tinge. It seems barely to move, so slow is its motion among the stars, for it takes two and one half years to pass through a single constellation of the Zodiac. Saturn has eight moons. Titan, its largest one, can be seen with a 3" glass. Its celebrated rings are telescopic objects but a small glass reveals them. URANUS. The student will hardly mistake Uranus for a fixed star, as it is only under the most favorable circumstances that it can be seen with the naked eye. At its nearest approach to the earth, it is as bright as a sixth-magnitude star. Uranus is accompanied by four moons, and takes seven years to pass through a constellation of the Zodiac. NEPTUNE. Neptune is the most distant of the planets in the solar system, and is never visible to the naked eye. The earth comes properly under a discussion of the planets, but a description of it is hardly within the scope of this work. Confusion in identifying the planets is really confined to Mars and Saturn, for Venus and Jupiter are much brighter than any of the fixed stars, and their position in the heavens identifies them, as we have seen before. The following table of first-magnitude stars in the Zodiacal constellations confines the question of identifying the planets to a comparison of the unknown star with the following-named stars: Castor and Pollux in Gemini. Spica " Virgo. Regulus " Leo. Aldebaran " Taurus. Antares " Scorpius. The first four stars named above are white in color, so that either Mars or Saturn is readily distinguished from them. As for Aldebaran and Antares, which are both red stars, not unlike Mars and Saturn in color and magnitude, the fact that the latter do not twinkle, and that they do not appear in the diagrams, should satisfy the observer of their identity. Reference to an almanac, or a few nights of observation, will in any case set at rest any doubt in the matter. [Illustration: THE PLANETARY ORBITS] [Illustration: COMPARATIVE SIZE OF THE PLANETS.] THE MILKY WAY.