planet, which are also subject to changes in their shape, and in the time of their appearing.

The next planet is Saturn, which shines with a pale, feeble light, and is about nine hundred millions of miles from the sun. His diameter is sup

posed to be upwards of sixty-seven thousand miles, and he performs his annual circuit round the sun in about twenty-nine years and a half.

The length of his day is about ten hours and a quarter. One of the first discoveries in astronomy, after telescopes were brought to a tolerable degree of perfection, was, that Saturn had a very different appearance from the other planets. In the year 1610, Galileo, a Florentine astronomer, and the inventer of the telescope, fancied that it was composed of three stars or globes—the largest in the middle, and a smaller one on each side; but it was found, by further observation, that what Galileo took for two smaller stars were parts of a thin broad ring, which surrounds the body of the planet without touching it, and which even is seen to be double when viewed through a good telescope. This ring is about twenty-one thousand miles in breadth, which is about its distance from Saturn on all sides, and it revolves with the planet on its axis. Astronomers conjecture, that it appears to the inhabitants of Saturn like a vast lu

minous arch in the heavens; but we are still ignorant of its use. This drawing may give you some idea of the rings. [See Plate 4.]

The most distant planet at present known is called the Georgium Sidus, or Herschel. It was first discovered by Sir William Herschel, on the thirteenth of March, 1781. He named it the Georgium Sidus in honour of our late king, George the Third; but it is very often called the planet Herschel after the discoverer, and I always prefer this name from its recalling the memory of that celebrated and indefatigable astronomer. As no spots have yet been observed on its surface, the time it takes to revolve on its axis is not known, so that we are unacquainted with the length of its days and nights; but it is calculated that its year is as long as eighty-four of our years. Its diameter is supposed to be thirty-four thousand miles, and it is about fifteen hundred and sixty-five millions of miles from the sun. Its light is of a bluish-white colour.

WILLIAM.

How many planets, then, are there altogether?

ELIZABETH.

Eleven Mercury, Venus, the Earth, Mars,

Vesta, Juno, Ceres, Pallas, Jupiter, Saturn, and Herschel.

MOTHER.

As the distances of the different planets from the sun are rather difficult to remember when they are expressed in miles, astronomers often express them in a shorter manner. They suppose the distance of the Earth from the sun to be one, and to be divided into ten equal parts, and make it a sort of standard to which the distance of the other planets may be compared. The distance of Mercury is estimated at four of such parts, that of Venus at seven, Mars at one and five parts, Jupiter at five and two parts, Saturn at nine and five parts, and Herschel at nineteen. The sun and the planets are also denoted by shorter marks or characters, instead of being written at full length. Here is a little table by which you may soon become acquainted with them :

And this engraving will give you some notion of the orbits of the different planets. [See Plate 4.]