Page images
PDF
EPUB

three belts, or dusky stripes, around him, and sometimes more.

Herschel has seen his whole surface covered with them.

He has four moons, Father.

The motion of light was ascertained by the eclipses of these moons. If we could see Jupiter from his nearest moon, he would appear a thousand times larger than our moon.

What a fine object he would be, Father! How I should like to see him! I should never forget the sight.

And so should I, Frank; but I was going to remark, that Jupiter has no inclination of his axis; he revolves on it in an upright position, in ten hours; so that his days and nights are always five hours long.

Then, Father, has he any change of season? You said that the change of our seasons was owing to the inclination of the earth's axis.

True; Jupiter can have no change of seasons; there must be perpetual summer at the equator, and perpetual winter towards his poles.

SATURN revolves around the sun next beyond Jupiter; he is known by his pale dead light; he never appears arrayed in the brilliancy of Jupiter. His diameter is nearly eighty thousand miles long; he is more than nine hundred millions of miles from the sun; he is but little less than thirty of our years going

round him. He travels more than twenty thousand miles in an hour; he has also seven moons and two rings: my book does not say, Father, whether the rings ever touch the planet; do they?

No; they are thirty thousand miles distant from any part of it. The largest of them, which is seven thousand two hundred miles broad, would readily include more than four hundred such worlds as ours. The inner ring is twenty thousand miles broad; the open space between the two rings is two thousand eight hundred and thirty-nine miles: and yet they accompany Saturn round the sun, and are never out of the place which God has assigned them.

Milton, Father, when viewing the works of God, calls them "glorious;" he might well say so, might he not?

Yes; and with what infinite propriety does he add: "THYSELF- how wondrous then!" How are they to be pitied, who can gaze on creation, and see nothing of its adorable Author!

Are these rings, by reflecting their light on the planet, as a compensation for his great distance from the sun?

This may be one of their uses; and his moons are evidently for this purpose. The rings, however, may answer ends with which we are unacquainted.

HERSCHEL, Father, is the remotest planet in our system.

So far as we know, Frank; it is the last which has been discovered. Saturn, a few years since, was thought the last,

Herschel is eighteen hundred millions of miles from the sun. What a distance! I should not like to live there; it must be very cold.

We are not sure of this, Frank; God may create warmth, if it be necessary, in many ways of which we have no conception.

He is about thirty-five thousand miles in diameter. He travels fifteen thousand miles an hour. He is eighty-three years and a half in going round the sun. There are six moons revolving round him. But as he has only been discovered a few years, how can any one know how long he will be going his course?

Easily; because we know how far he has to travel; and if we know how great a distance he has gone in twenty years, of course he will go the same distance in twenty more, and so on.

I do not understand how you know that Mercury and Venus revolve in orbits between our earth and the sun.

I will tell you; they are never seen in opposition to the sun; when in the morning the sun is in the east, they are never on the west

[ocr errors]

ern side of the heavens; when the sun is in the west, they are never in the east.

You have never shown me Herschel, Father. I should very much like to see him.

No; he is not a star of the first magnitude, and his distance is so great, that he is seldom seen by the naked eye. I will show him to you some fine evening through the telescope.

And I cannot think how you find out the distances of the planets from the sun, by being acquainted with that of the earth.

Listen, Frank, and you shall hear; Kepler, a celebrated astronomer, discovered that the times which the planets take in revolving round the sun, are proportional to the cubes of their distances from the sun.

I scarcely understand you, Father; but will you tell me how you know the distance of Mercury from the sun?

Why, easily; by the rule of three: the earth is 365 days in revolving around the sun; Mercury is 88 days; and the earth is ninetyfive millions of miles from the sun so, the question may be stated thus; as the square of 365 days is to the square of 88 days, so is the cube of 95,000,000 to a fourth number; which, of course, is easily found by the rule.

And does it give you the distance of Mercury from the sun?

No; but the cube root of that number will give you the true answer.

I could easily calculate this, Father. I am sure you could; it is very easy. But there are COMETS, Father, belonging to our system; are there not?

Yes; but we know little that is certain in reference to them.

The account which you gave me, Father, says that the comet which Sir Isaac Newton saw in 1680, was two thousand times hotter than red hot iron; was it so, Father?

I cannot tell, Frank; I know nothing of a heat so stupendous as this: much deference, however, is due to the calculations and opinions of this great man.

And Sir Isaac also says that it moved at the rate of 880,000 miles an hour.

The tails of some comets have been thought more than forty millions of miles long. But you shall read more about the subject when you are older.

But, Father, you have said nothing about the fixed stars.

They do not belong to our system; I have shown you the pole-star, and you know how to find it; and you know most of the constellations.

I always think of you, Father, when I see the pole-star; and I recollect, as you told me, that when I am looking at it, I am looking towards the north; the south is behind me; the east is on my right, and the west, of course,

« PreviousContinue »