comfort in the words that utter his own sorrow, a voice for his unspoken cry for help in that invocation:

'Strong Son of God, Immortal Love,

Whom we, that have not seen Thy face,

By faith, and faith alone, embrace,
Believing where we cannot prove ;

"Thou wilt not leave us in the dust :

Thou madest man, he knows not why;
He thinks he was not made to die;

And Thou hast made him: Thou art just.'

The moods of sorrow are many and various. Part at least of the fascination of In Memoriam' lies in the range of moods which it covers, so that one can hardly fail to find the moment's feeling expressed somewhere or other in the poem-the inarticulate grief made articulate with a strange perfection that brings with it a wonderful relief. I would that my tongue could utter the thoughts that arise in me.' It is the poet's gift to men to have uttered what they could only feel before.

ARTHUR D. INNES.

SUN-RAYS AND STAR-BEAMS.

BY AGNES GIBERNE, AUTHOR OF 'SUN, MOON, AND STARS,' 'THE
WORLD'S FOUNDATIONS,' 'THE OCEAN OF AIR,' ETC.

II. THE NATURE OF LIGHT.

It has

A STAR for us has no apparent size. It has no breadth. no width. It has no disc. Measurement there is not possible. Each separate star is one single point of light, which cannot be halved. We see the whole of a star, or we do not see it at all. A planet shows size and may be measured. A planet grows larger, when nearer, or when seen in a telescope; but a star never grows larger, no matter how powerful the magnifier used. It grows brighter; not apparently bigger.

One cobweb line will utterly hide a star. Though the orb at which we gaze may be a vast and glowing sun, perhaps scores of times as large as our sun, yet the whole of its glorious radiance comes to us, narrowed down to one single beam of light.

Still, though a star's size cannot be measured, we know with almost certainty that some stars are larger than others; that some must far surpass our sun in size. If the distance of a star has been found out, and if it is calculated that our sun at that distance would not shine half so brilliantly as the star shines, then it follows, as a matter of reasonable belief, that the star, while possibly brighter, is also very probably larger than our

sun.

All this, however, is an affair of conjecture, not of measurement. No single star in the whole heavens, outside our Solar System, has yet proved susceptible of measurement. The distances of a few, approximately, we can find out. The sizes of all are beyond our grasp.

We talk of Star-Magnitudes, but the term is wrong. A star of the First Magnitude is really a star of the First Order of Brightness. No question of size is necessarily involved. The brighter star may be the larger; or it may be only the nearer.

All, absolutely, that we know of a star is built upon a Ray of Light.

Other senses fail us here. We cannot touch, we cannot hear, those distant orbs. No sound from them of roaring flames can ever reach our ears; for sound is carried by air; and a few miles, or at most a few hundred miles from Earth's surface, air ceases. In solemn silence-silence, so far as human powers of hearing are concerned-century after century the countless Suns of the Universe roll onward. Sight alone speaks to us of their wonders; and Light alone can speak to Sight.

To some extent we may say the same of our sun; but there we have bodily consciousness of heat, as well as of light; and the power of the sun is visible everywhere about us, in an infinitude of ways. Even the paler and more insignificant moon makes herself felt as well as seen in our lives. Every time that we hear ocean's tides pouring in or out, we hear the utterance of moon power. Moreover, in the case of sun, moon, and planets, the rays of light are many, the surfaces to be examined are more or less extended. The sun has his spots and streaks; the moon has her mountains and hollows; the planets have their various characteristics of polar spots, or bands, or diverse hues.

With the stars all such landscape features are lacking. Each one, whether the brightest or the dimmest, has for us no surface, no disc, no shape, no apparent size; nothing but light, brought down through exceeding distance to a slim indivisible shaft of radiance. Indivisible in one sense; not in another. More of this later. Our whole knowledge of that faroff sun is founded upon one continuous beam of brightness. Where sight fails, the stars for us cease to exist, except in imagination. We do not feel their heat, or see upon earth results of their power.

In trying to picture to ourselves what is meant by LIGHT, two sides of the matter claim attention: the ray of light itself, and the eye which receives that ray.

We are apt to think of light as being instantaneously everywhere; but this is error. Light is given out by a bright bodywhether candle or lamp, sun or star-in what we are pleased to call rays or beams; and those rays or beams travel at a certain rate of speed. A ray starting from the sun, or from a star, is not immediately here, any more than a train starting from London is immediately at Liverpool. Time is occupied in either journey.

The speed of light has been repeatedly measured in divers modes; one result proving another, as when we add up a sum in two different ways, to see if the answers agree. Slight corrections have been made from time to time, due to increased delicacy of instruments, and increased accuracy of observation. Here is the result: that light journeys at the rate of 186 thousands of miles each second; or, roughly, at the rate of 600 billions of miles each year.

If you have seen a gun fired, or a rock blasted, at some distance, you must have noticed that the flash was first visible. Then, after a brief pause, followed the bang of sound. So, too, in a thunderstorm: first the lightning is seen, then the thunder is heard.

The reason for this is that, while sound and light both require time to travel, sound is very much slower than light. They start on their way at the same instant, but sound lags behind, and light speeds forward. Sound travels at the rate of 1140 feet in one second; and light travels at the rate of 186,000 miles in one second. A very considerable difference! No wonder the light of an explosion reaches our eyes before the sound of it can reach our ears.

Nevertheless, extraordinarily rapid as light is in motion, it does journey, and it does occupy time in journeying.

Light coming from the sun by no means touches earth at the identical instant that it quits yonder blazing surface. A ray of sunlight, which reaches London at precisely mid-day, left the sun at close upon nine minutes to twelve of London time. Through those nine minutes the ray has flashed through space at the rate of over eleven millions of miles each minute, till arrested by earth.

A soft moonbeam, touching your face or mine, quitted the moon less than one minute and a half ago. One might suppose that light from the radiant sun would journey faster than a pale weak moonbeam. But, no! Light, whether it spring from sun or moon, lamp or candle, whether direct from a blazing body, or only reflected from a dark body, travels always at the same speed.

When we seek to realise the distances of the stars, no better measuring-line can well be found than this of light-speed. Nine minutes' journey from the sun means what we count to be an enormous space. Yet this great dividing gap sinks into a mere rift, beside the stupendous chasm which divides the SOLAR

SYSTEM from the stars. Here we take for our yard-measure,' not the speed of light each second,-186,000 miles,-but the speed of light each year,-600 billions of miles,-and we reckon the distances of the stars in so many years of light-journeying.

Viewed thus, we find that while the moon is less than one and a half minute distant, and the sun less than nine minutes distant, the very nearest known to us of all the fixed stars, Alpha Centauri by name, lies FOUR YEARS AND FOUR MONTHS

AWAY.

Think what this implies. We sometimes say, speaking of a town, 'Oh, it is one hour away!'-meaning one hour of railway travelling, at perhaps forty miles an hour, with stoppages. In like manner one might say, 'Oh, the moon is not one minute and a half away!' or, 'Oh, the sun is nearly nine minutes off!' as if that were a slight matter. But of the stars, in a more awe-struck tone we must say, 'The nearest is almost four years and a half away!' And this nearest--the very closest neighbour known to us in the Universe, outside our Solar family-this Alpha Centauri, lies about ten billions of miles nearer than any other star, the distance of which has yet been measured.

A light-ray, whether from sun or star, world or moon, lamp or candle, or any kind of body, either giving out or reflecting brightness, travels always in straight lines, unbending and unbroken, so long as it continues in one medium, or in different mediums of exactly the same density. But if it passes out of one medium, and enters obliquely another of different density-as in passing out of air into water, or out of glass into air-it is bent or REFRACTED into a new direction. Water is much more dense in make than air; therefore, a ray of light, passing obliquely out of air into water, or out of water into air, is sharply refracted out of its former course in the act. air; and a ray of light, passing other, shows the same result.

Glass is much more dense than obliquely from the one to the

Drop a penny into a cup, and stand so that the coin is just hidden from your eyes by the cup-rim. Then, without moving your head, pour, or get some one to pour, water slowly into the cup. The penny will quietly rise to view, even while the rim of china is still interposed between it and your eyes. For the rays of light, which proceed from the surface of the coin, are bent out of their straight course at the moment of quitting water for air, and thus they reach your eyes. So here you have a case of