Part 12

The wind, rejoicing in its power to drive the clouds, now flew upon the ocean and buffeted the waves. Affrighted at its blows, they fled hither and thither in their distress, and mingled their roar of terror with the shrill shrieks and cries of their invisible foe.

It was a storm. The captain, who had been attentively watching the signs, and losing his breakfast, saw what was coming, and prepared for it. The sails were taken in, and the ship made snug and safe. The storm came with a wild burst all at once, and reeled the vessel almost upon its side. But the officer was there, the helmsman was awake to his duty, and the lounging barque kept on her course in spite of her erratic movements.

James was not insensible to fear. He was but a boy. And when, in addition to the noise of wind and billows, the thunders came pealing from the heavens, he instinctively clapped his fingers to his ears, as if to drown the sound and his fears. The vivid stream of lightning, as it darted from cloud to cloud, played round the ship, or plunged madly into the sea, added to the interest and the terror.

But the echoes died away to whispers. The clouds put on their snowy robes. The ripples gently laughed on the bosom of the ocean. The sun, no longer angry, smiled kindly upon the scene. In the evening, a few lines of vapour were motionless in the sky; and the long, uncertain heavings of the waters told that a calm was softly ruling all.

The boy was found by his father looking at the placid face of the heavens.

“What, boy! at your old post, staring at Orion again.

I’ll tell you what I was thinking of, father. You see the world is like this ship--always on the rock, never really still--and I was thinking how pleasant rest is, and what a lot of it they must get up there in the fixed stars.

Not so; we are now learning that they are, like some boys, not so steady as they look.

You surely don’t mean to say that such respectable old folks as Sirius and his bright friends ever go dancing about in the heavens like giddy Venus and Mercury? I know they appear to tumble about over our masts in a storm at night, but that is because the ship is rolled over by the winds and waves.

It is really true that they do not keep to their places, though the change of position is so very slight as not easily to be discovered. Your friend Sirius, for instance, has been closely watched, Dog as he is, for two thousand years. We know what his place was that time ago, and what it is now; and it has shifted to the southward half-a-degree.

That is as much as the apparent diameter of the sun. But has he any company in his rambles?

Yes; the Bull’s Eye, Aldebaran, has kept up pace with him.

Quite right to have an Eye upon the Dog. But has any exact difference of position been observed since we have had good telescopes?

The star sixty-nine of the Swan has been well watched for fifty years, and found to have gone on four minutes--the eighth part of the moon’s face. A star in the Indian has moved seven seconds in the year. They are not fixed, like the ancients thought they were, in a crystalline sphere; or riveted, as Aristotle taught.

Pray, is our sun no more fixed than the rest of them?

He, too, is on the move.

But where are they all going to?

That has been a matter of dispute. Some thought the stars were dancing round Sirius. But Mädler, the German astronomer, would have us believe that they have a greater fancy for some spot near the Pleiades. Others think of Hercules. But all would take many millions of years.”

DISTANCES AND SIZES OF THE STARS.

James had a long talk with the captain one day about the telescope, and got a capital lesson about the magnifying power being according to the character and size of the glasses used. The sailors called the instrument the “Bring ’em near;” and it does make distant objects look as if near. It was explained to the boy that the stars were of different magnitudes or sizes, first, second, third, &c., according to their relative distances. The following conversation followed between the father and son:--

“Now, my boy, I must try and give you some idea of the penetrating power of light, that you may get an idea of the enormous distances of the stars. You are aware that the more distant they are the less their light. A star of the first or nearest magnitude will have one hundred times the light of one of the sixth magnitude. A telescope, therefore, gathering one hundred times the ordinary light, will make the sixth look as near as the first.

And will it be one hundred times further off?

No; light increases or diminishes according to the square of the distance.

I know. If the light be one hundred times less, the star will be ten times further off, for the square of ten is one hundred. I can understand now that a thing is only seen by the help of light. I do not see many stars, because their light is too little for my eyes to take in. The telescope has bigger eyes to take in the light of the distant stars and nebulæ.

The pupil of the eye is but one-eighth of an inch in diameter. An object glass of twelve inches diameter is, therefore, ninety-six, or say one-hundred times as long. As the light seen is according to the square of the diameter, the telescope of twelve inches will receive one hundred times one hundred, or ten thousand times more light.

But is there a way of measuring the quantity of light?

There is. We find that the sun has twenty-two thousand millions of times more light than the nearest of the fixed stars.

Then, the square root of this ought to tell how much further off it is. Let me see. It will be about 150,000.