surrounded by its several primary planets. These are now to be reckoned twelve in number. You will perceive that the names of eleven are Mercury, Venus, the Earth, Mars, Jupiter, Saturn, Herschel; and those of the four smaller planets, Vesta, Juno, Pallas, and Ceres; to which is to be added a fifth new and minute planet or asteroïd, discovered at the latter end of the year 1836, by the Italian astronomer Cacciatore.

They are all great bodies, but some are bigger than others. The five last are smaller than the rest, and are sometimes called asteroïds; which latter word means bodies that are only planet-like or star-like. Planets and stars are often equally called stars."

Now these twelve planets, or seven planets and five asteroïds, are at different distances from the sun. They are all at immense distances,

What are the names of the seven planets?
What of the five asteroïds?

What is the meaning of the word asteroïd?

the nearest being thirty-seven millions of miles from the sun, while the furthest is eighteen hundred millions of miles.

It is difficult, if not impossible, to form any conception of such vast distances. The earth is ninety-three millions of miles from the sun. Now the wood-pigeon is one of the swiftest birds that flies, and it will fly about two miles in a minute. Yet it would take a pigeon, were it to fly with its utmost speed, night and day, at least one hundred years, to go from the earth to the sun.

You will bear in mind, that some of the planets belonging to the Solar System are visible to the naked eye, and that some are not. All the seven primary and larger planets may be seen

How far is the nearest planet from the sun? How far is the most distant planet? How far is the earth from the sun? How long would it take a pigeon, even if it could fly constantly, to fly from the earth to the sun?

Are all the bodies belonging to the solar system visible to the naked eye?

on a clear night. One of the asteroïds, or lesser though still primary planets, may also sometimes be seen. All these bodies are continually changing their places in the sky. At one time, Jupiter may be seen at one part of the heaven; a few weeks after, it will be seen in another part; and the same may be said of all the other bodies (the Earth and the Comets inclusive) which belong to the Solar System. It is this which distinguishes the planets from stars, both in name, and as they are seen and watched in the heavens; and causes them to be called planets.

Which of them are visible on a clear night?

Are the planets always in the same place?
What of Jupiter?

Why are the planets so called?

CHAP. XXXVII.

PARLEY TELLS ABOUT MERCURY.

I WILL now tell you about Mercury. This is the nearest of all the planets to the sun. Yet it is thirty-six, or thirty-seven, millions of miles from the sun.

It revolves round the sun once in about three months, and turns on its own axis once in about twenty-four hours. It is seldom seen with the naked eye; but, observed through a telescope, it exhibits nearly the same phases as the moon. That is, sometimes it appears to be round, and sometimes but partly round. These various appearances are to be accounted for in

Which is the nearest planet to the sun? How far is Mercury from the sun? How long is it revolving round the sun? How long does it take to turn round on its axis? How does Mercury appear through a telescope?

to be accounted for?

How are its various appearances

the same way as the various appearances of the

moon.

Mercury is the smallest of the seven larger planets. It travels round the sun at the rate of one hundred and ten thousand miles an hour. Being the nearest planet to the sun, its light is exceedingly brilliant; and its body and atmosphere are imagined to be seven times as hot as on the earth. It is said, that if there were water there, it would be immediately converted into steam; and that lead and tin, if such things are there, must be always in a melted state.

It is because of its nearness to the sun, that we can comparatively seldom see the planet Mercury. It travels with the sun, and is visible. for not more than two hours before the rising of the latter, and for not more than two hours after

Which is the smallest of all the planets? does Mercury travel in an hour?

How many miles

What of its light and heat?

How would water, lead, and tin, be affected, as it is sometimes

thought, by the heat, in the planet Mercury?