and giving forth again the rays of sunlight, she serves us often for a night-lamp. And if it were not for the steady, ceaseless power of her attraction, as exerted on ocean-waters, the whole system of tides throughout the world would be different from what it now is-with consequences which we can hardly calculate.

"Then out of the east in a paling mist,

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The dead-faced Moon came up to be kissed;
Slow and solemn, we watched her rise,

A face of wonder with cavernous eyes.

There life is changeless, and time without worth,
There nothing dies or is brought to birth;
Her day is done, she is filled with dearth;
Old she looks to the young green Earth,
Old as the foam of a frozen shore,
Old-for nothing can age her more.

O young green Earth, go down into night,
Rejoice in thy youth, till its days are o'er;
Time speeds, life spends; therein is delight
Till youth and the years can age no more.

1 From The Heart of Peace and Other Poems, by Laurence Housman. Pub.: William Heinemann. By permission.

PART V

THE FAIR WORLD VENUS

I. COOLING BODIES

We will turn now from the thought of our very near neighbour to another bright world in the sky, belonging to the Family of our Sun-beautiful Venus.

It should at the outset be fully grasped that when "bright worlds in the sky are spoken about, stars are not meant. Those countless twinkling specks of light, which night by night spangle the heavens, are not "worlds."

True, a star may conceivably be on the road to becoming a world. But that road is very long; and the goal may lie at an enormous distance ahead.

Each separate star which we can see is in all likelihood a brilliant sun, larger or smaller, brighter or fainter, than our Sun, clothed like him in an ocean of fiercely-raging gases, shining like him with its own terrific heat.

Also, each separate star is, in all probability, parting with its abundant stores of heat; and unless by some means those lost stores can be replaced, it must become, in the far-distant future, a cooled and therefore a nonshining body. When so cooled, and not before, it may possibly deserve to be classed as a "world," instead of

as a sun.

sun;

On the other hand, it may be only a dark " and such dark suns are believed to be many in number, scattered widely through the skies, like derelict ships on the ocean.

Whether it can then possess any brightness will depend on whether it is near enough to any radiant sun to reflect the rays of the latter. If it can do this, it will still be too dim to be visible to us from so great a distance.

And even then, if it does catch and cast forth such light, unless it actually belongs to that radiant sun, unless it is controlled and warmed and lighted by him, it could hardly be called in the usual sense "a world."

No world in the sky, properly so named, shines to any very marked extent by reason of its own intrinsic brightness, but mainly at least, if not entirely, by reason of the light of its sun; through borrowed radiance.

Venus and Mars and Mercury would not be bright worlds at all, but only dark bodies, invisible here, if they were not clothed in the Sun's rays. Jupiter might indeed be dimly visible, and Saturn very much more dimly, since these great planets are now believed to give forth some amount of light, though a very much smaller amount than what they show to us. And other worlds in the Universe, belonging to other suns, which we may be pretty confident do exist albeit we cannot see them, would probably be in the same condition.

A "world" in the language of Astronomy does not of necessity mean one in which people live, or even one which is in a fit state to be inhabited. It means simply a lesser member of a sun-system or family; generally

a body which has once been extremely hot and has now lost a large degree of its heat, although in some instances it may still give forth a good deal, and may even shine to some extent.

We call a house "a house," whether it is full of people or quite empty, whether it is in good repair or unfit for use. And we call a cooled heavenly body, belonging to some central sun, a "world," whether or not living creatures could or do find a home on it.

Any single planet in the sky, whether among the many worlds of our Solar System, or whether in other parts of the Universe and much too far away for their soft shining or their reflected light to be able to reach our eyes, may have been formed for the express purpose of sooner or later supporting Life. It may be an inhabited sphere now. It may have been inhabited long ago, in ages past. It may be going to be inhabited by-and-by, in centuries or millenniums still distant. In such cases we cannot get beyond a may-be."

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The very existence of such worlds, lying far beyond the limits of our Solar System, can only be a matter of conjecture, though with many minds the conjecture means very strong probability.

But as to the question of life in them, any such life as we know here-and even of life in the worlds which we do know to exist, because we see them in our skywe still have only conjecture to help us.

True, we may form some idea as to which of our neighbour-planets seems to be more likely than others. to have reached a stage which is possibly fitted for some kind of living inhabitants. Yet the said idea has to be built largely on a foundation of "perhapses."

II. THE PATHWAY OF VENUS

Of all the planets in our System, Venus comes first in brightness and beauty. Not only is she, from our point of view, the fairest, and the most easily found and followed, but also she is the one-with the exception only of a tiny minor planet-which at intervals draws most closely to Earth. In some ways she may be looked upon as Earth's twin-sister.

Though in the following lines Wordsworth does not speak of her actually by name, his meaning is evident— 'Why repine,

Now when the Star of Eve comes forth to shine
On British waters with that look benign?
Ye mariners that plough your onward way,

Or in the haven rest, or sheltering bay,

May silent thanks at least to God be given

With a full heart-our thoughts are heard in Heaven."

And again, we have from Longfellow

"Lo, in the painted oriel of the West,

Whose panes the sunken sun incarnadines
Like a fair lady at her casement shines,
The Evening Star, the star of love and rest."

She is a

But Venus, as explained before, is no star. cooled and dark body. When the Sun shines on any part of her surface, that part shines in response; when any part is turned away from him, that part is in darkness. In size she matches our Earth, being slightly smaller. The diameter of Earth is 7927 miles, that of Venus is 7701 miles.

Both journey round the Sun, each in its own pathway; that of Venus lying inside that of Earth, while that of Mars is outside that of Earth.