Comets revolve round the sun like the planets, except that their orbits are far from being so nearly circular, but on the contrary they are exceedingly elliptical, or of an oblong oval. Some of them pass round the sun at a shorter distance than Mercury, and then shoot through an immeasurable space, even beyond the orbit of Uranus. Most comets we know so little of, that when they disappear it is impossible to tell when or whether they will return. There are a great many comets, five hundred are recorded as having been seen since the beginning of the Christian era; that is, within the last one thousand eight hundred and thirty-seven years.

Comets, you will remember, revolve round the sun, and form parts of the Solar System.

Do comets revolve round the sun? orbits? What is an elliptical orbit?

What is the form of their
How near do comets

come to the sun? To what distance from the sun do they someDo we know much of comets?

times go? How many of them have appeared in the last one thousand eight hundred and thirtysix years? Do comets form parts of the Solar System?

Some are supposed to be but a few years in performing their revolutions, and others several hundred years.

Many comets are always invisible to the naked eye. It is believed that, visible or invisible to the naked eye, at least two comets approach the sun, and make their circuit round it, within the period of each year. The telescope discovers to us this real frequency of comets.

Of the extraordinary figures of particular comets there are numerous accounts.

What

you observe the nucleus or disc, and part of the lengthened tail.

The figure over leaf is that of the comet of 1744, according to M. Chezeaux; and one of the most remarkable upon record. The tail is divided into six branches, all diverging like the sticks of a fan, and between them the stars are visible. Remarkable, however, as was the figure of this comet, I wish you to take particular notice of it, because of its resemblance to the telescopic accounts of the comet of 1835 and 1836.

The nucleus of the comet, and the roots, as it were, of the tails, appear in that part of the figure which is only outlined. My little readers most suppose a vast space in the heavens, between the upper part of the outlines and the finished ends of the tails. These, however, in this comet, were only reckoned at a length of thirty degrees; whereas, the simple tails of many have exceeded sixty degrees, and even ninety.

CHAP. LI.

SOMETHING MORE ABOUT COMETS.

COMETS, or cometary stars, have their name from the word coma, signifying "hair;" so that the real meaning of the word comet, is "hairy star." But again, by "hair,” in speaking either of a comet, or of the sun, is meant its rays of light, or the light which either appears to issue from it, or by which it is surrounded. It is because of the rays of the sun, that Apollo (the personification of the sun, or the sun spoken of as if it were a man or person) is said to have yellow or golden hair. And thus it is that you must understand the name of "hairy star," and the expression of the "horrid hair" of a comet, when the same Milton

says, that Satan,

"like a Comet burned,