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sign i, the head of a spear. To Juno, the third planet, was assigned o, a sceptre surmounted with a star, the emblem of the queen of heaven. An altar with fire upon it, fi, appropriately represented Vesta, the household goddess, whose sacred fire was kept burning continually. In this way names of goddesses and appropriate symbols were used to designate the minor planets which were earliest discovered. Since then a simple circle with the number inclosed has been adopted; thus ® represents Ceres—@ is the sign of Pallas.
The king of the gods. Sign y, a hieroglyphic representation of an eagle "the bird of Jove."
Description.—From the smallest members of the solar system we now pass at once to the largest planet—the colossal Jupiter. Its peculiar splendor and brilliancy distinguish it from the fixed stars, and vie even with the lustre of Venus. It is one of the five planets discovered in primitive ages. In those early times, Jupiter was supposed to be the cause of storm and tempest. Pliny thought that lightning owed its origin to this planet. An old almanac of 1368, foretelling the harmless condition of Jupiter for a certain month, says, "Jubit es hote and moyste and does weel til al thynges and noyes nothing."
Motion In Space.—Jupiter revolves about the sun at a mean distance of 475,000,000 miles. His orbit has much less eccentricity than those of the smaller planets. Were his path very elliptical, the attraction of the sun would be insufficient to bring him back from its extreme limit, and the huge unwieldy planet would plunge headlong into space. This careful fitting, whereby the plan is always modified to accomplish an end, is everywhere characteristic of nature, and is a continued revelation of its common Author. The revolution of Jupiter among the fixed stars is slow and majestic, comporting well with his vast dimensions and the dignity conferred by four attendant worlds. He advances through the zodiac at the rate of one constellation yearly; so that if we locate the planet now, a year hence we can find it equally advanced in the next sign. Yet slowly as he seems to travel through the heavens, he is bowling along through space at the enormous speed of 500 miles per minute. The Jovian day is only equal to about ten of our hours, while his year is lengthened to about 12 of our years, comprising near 10,000 of his days.
Distance From Earth.—Once in thirteen months Jupiter is in opposition, and his distance frorn the earth is measured by the difference of the distances of the two bodies from the sun. At the expiration of half this time he is in conjunction, and his distance from us is measured by the sum of these distances.
Dimensions.—Its diameter is about 88,000 miles, or one-tenth of the sun. Its volume is 1,400 times that of the earth,
and much exceeds that of all the other planets combined. Seen at the distance of the moon, this immense globe would embrace 1,200 times the space of the full moon. Jupiter's density is only one-fifth that of the earth; moreover, its rapid rotation upon its axis, whereby a particle on the equator revolves with a velocity of 467 miles per minute against the earth's 17 miles per minute, must produce a powerful centrifugal force which materially diminishes the weight of all objects near its equator. Consequently a stone let fall on Jupiter would pass through but about thirty-nine feet the first second. As a result of this rapid rotation, the planet is one of the most flattened of any in the solar system—the equatorial diameter exceeding the polar by about 5,000 miles.
Seasons.—As the axis of Jupiter is but slightly inclined from a perpendicular to the plane of its orbit, there is but little difference in the length of its days and nights, which are each of about five hours' duration. At the poles the sun is visible foi nearly six years, and then remains set for the same length of time. The seasons also are but slightly varied. Summer reigns near the equator, while the temperate regions enjoy perpetual spring. The light and heat of the sun are only -fa of that which we receive; yet peculiarities of soil or atmosphere may compensate this difference. The evening sky on Jupiter must be inexpressibly magnificent; besides the glittering stars which adorn our heavens, four moons, waxing and waning, each with its diverse phase, illuminate its night. All the starry exhibition sweeps through the sky in five hours.
Telescopic Features.—Jupiter's moons.—Under the telescope Jupiter presents a beautiful Copernican system in miniature. Four small stars—moons—are seen to accompany it in its twelve-yearly revolutions. From hour to hour their positions vary, and they seem to oscillate from one side to the other of the planet. At one time there will be two on each side, and again, three on one side; while the remaining star is left alone. They are also frequently found to disappear, one, two, or even three at a time, and, more rarely, all four at once. There are wellauthenticated instances on record of their having been seen by the naked eye. Among others, the following singular case is mentioned. Wrangle, the celebrated Russian traveller, states, that when in Siberia, he once met a hunter, who said, pointing to Jupiter, "I have just seen that star swallow a small one and then vomit it up again." These moons are called by the ordinal numbers, reckoning outward from the planet. With an ordinary glass, there is nothing to distinguish them from small stars. The HId, however, being the largest and brightest, will generally be identified easiest. The 1st satellite appears to the inhabitants of the planet almost as large as our moon to us; the lId and HId about half as large. Their real size and density are indicated in the following table. It, will be seen that the IVth is about the weight of cork, and the 1st and lId are still lighter.
Satellites Of Jupiter.
It is noticeable that here are four satellites revolving about Jupiter, one of them larger than the planel Mercury, and each far surpassing in size the minor planets between Mars and Jupiter. The moons are not only thus distinguished by their various dimensions, but also by the variety of their color. The 1st and lId have a bluish tint, the IHd a yellow, and the IVth a reddish shade. The total space occupied by this miniature system is about two and a half million miles in diameter.
Eclipseof the moons.—Jupiter,like all celestial bodies not self-luminous, casts into space a cone of shade.