If the Sun really were, as used to be thought, just as near to us as the Moon, he would be an appalling object. Not alone from his colossal size, but because of the ocean of furious fiery gases which enfold his whole surface, and because of the fierce and whirling storms, the fearful heat, the scorching glare.

Could such an event come to pass, as that the Sun should approach to where the Moon now is, then at any instant vast tongues of glowing hydrogen gas-great crimson "flames "-might leap from the Sun and enwrap our little Earth in their fervid embrace. Such mighty outbursts are no rare matter on the Sun, sometimes reaching to a height of more than three hundred thousand miles. And the Moon is only two hundred and forty thousand miles away from us.

But that the Earth should remain in her present position, moving still at her present speed, under such circumstances, would be impossible. So terrific would be the force of the Sun's attraction that, long before he could draw thus near, she would have leapt with lightning speed to greet him, and would have been lost in that fierce tumultuous sea of fire, as a pebble drops and is lost in the ocean.

While therefore we may be thankful for the light and heat bestowed upon us by the Sun-without which we could not live-we may also be thankful that he is placed at a safe distance. We may congratulate ourselves that it is not the raging and storm-driven Sun, but the cold and quiet Moon which lies only a few thousands of miles away; even though the poet Tennyson did look upon her as a rather unsympathetic friend, when he

wrote

Oh, a cold, cold glance hath the Lady Moon,
And a stately step, and slow,

As with queenly gaze, so proud and pure,
She looketh on all below.

"She pauseth not on her onward path,
To list to the mourner's sigh;

She pitieth not the throbbing pulse,
Nor the dim and sunken eye."

Still, if somewhat impassive, she is constant in her attachment. And it is better to depend on her steadfast shining than to have only the will-o'-the-wisp flash of a shooting-star, or the uncertain visits of a comet. We do at least know when we may expect her; and she never fails to arrive punctually to the minute.

It is fair, however, to add that Shakespeare did not, through the voice of one of his characters, allow her even the virtue of steadfastness

"O swear not by the Moon, the unconstant Moon,
(That monthly changes in her circled orb)—
Lest that thy love prove likewise variable.” 1

So though the Sun and Moon fill much the same space in our sky, this does not mean that they are the same in bulk. Far from it! The Sun is enormously the larger of the two, and also he is immensely farther off. To the latter fact is due their seeming likeness in size. The very much greater distance lessens hugely his apparent not his real-size. A man who is fifty or a hundred yards away may look to our sight much bigger than a house which is half-a-mile or a mile away, yet that does not make him as large as the house.

Our Moon's distance from us is not always exactly

1 Shakespeare: Romeo and Juliet.

the same. She travels round in a pathway, or orbit, which may be described as slightly oval in shape, and the Earth is not at the precise centre of that oval.

In one part of her monthly tour she is more than twenty-six thousand miles nearer to Earth than in another part. The two hundred and forty thousand miles which-speaking roughly separate her from Earth, though a good deal when compared with distances on Earth itself, form a very insignificant little gap when compared with the wider heavenly distances which separate star from star.

III. SIZES AND DISTANCES

Before saying more about the Queen of Night, it may be well to pause, and try to give a general notion of the sizes of a few leading members of our Solar System, and of the distances separating them one from another.

A train has been already imagined as going steadily at the rate of fifty miles an hour, never slackening or pausing night or day, travelling direct from one side of our Earth to the other, straight through the centre. Such a train, starting perhaps in the neighbourhood of the British Isles, and coming out in the neighbourhood of Australia, might accomplish its journey in less than a week. The same train, always at the same speed, with no stoppages, may be pictured as making the following journeys

Round the whole Earth, on the equator, in nearly three weeks.

Through the centre of the Moon, from one side to the other, in about two days.

Round the whole Moon, on the Moon's equator, in about six days.

Through the centre of the Sun, from one side to the other, in nearly two years.

Round the whole Sun, on the Sun's equator, in something under six years.

If you master these simple figures, you will gain a fairly clear idea of the relative sizes of Earth, Moon and Sun.

Then about the distances of certain planets from ourselves of Venus, Mars and Jupiter the most easily seen in our sky. With them we will take the nearest positions. Each planet is sometimes on the same side of the Sun as our Earth, and at certain dates each one comes into a direct line with both Earth and Sun. That is the very closest point to which each planet draws. At other times each may be very far away, right off on the other side of the Sun, and then the dividing gap is immensely increased.

It may help you to gain an idea of how this comes about if you place on the floor a small ball, then drop round it, lying flat, a small hoop. Round that lay a second and bigger hoop; round that a third, still larger; and round that a fourth, much larger still. The ball in the centre is the Sun; the smallest of the hoops is the pathway of Venus round the Sun; the next is the pathway of our Earth; then comes the pathway of Mars; and, lastly, you have the pathway of Jupiter. Other planets, nearer or farther than these, we are leaving alone for the present.

Suppose that a very tiny ball is journeying round

D

and round each hoop, moving at different speeds. Those nearer to the central ball go faster, those farther out go more slowly. So sometimes one on one hoop overtakes another on the next hoop, or lags behind it. Sometimes two are quite near together, and sometimes they are on opposite sides of the little ball which lies. between them. That is how the planets travel round the Sun.

Only there are many more of them than those three, and the pathways, or orbits, are not round, but slightly oval, and the distances between those various pathways are wide.

Each one of these chief planets keeps always to its own orbit. Not one of them ever invades the orbit of another. Venus never gets near to the Earth's orbit from one side, and Mars never approaches it from the other.

Now imagine the same train as before, always at the same unchanging speed, making the following trips— Straight from the Earth to the Moon in less than seven months.

Straight from the Earth to the Sun in about two hundred and ten years. See what a contrast there is between the space which separates the Moon from Earth, and that which separates Earth and Sun. Next come certain planets.

Straight from Earth to the planet Venus, when the two are at their very nearest points, in rather less than sixty years.

Straight from Earth to the planet Mars, when at their nearest, in somewhere about eighty years.

And straight from Earth to the huge planet Jupiter,