The fact that the moon shows phases signifies that she shines only by reflected light; and it is surprising to notice how little of the light that falls upon her is really reflected by her. On an ordinarily clear night most people would probably say that the moon is much brighter than any terrestrial object viewed in the daytime, when it also is lit by the sun, as the moon is. Yet a very simple comparison will show that this is not so. If the moon be compared during the daytime with the clouds floating around her, she will be seen to be certainly not brighter than they, generally much less bright; indeed, even an ordinary surface of sandstone will look as bright as her disc. In fact, the reason of her great apparent brightness at night is merely the contrast between her and the dark background against which she is seen; a fragment of our own world, put in her place, would shine quite as brightly, perhaps even more so. It is possibly rather difficult at first to realize that our earth is shining to the moon and to the other planets as they do to us, but anyone who watches the moon for a few days after new will find convincing evidence of the fact. Within the arms of the thin crescent can be seen the whole body of the lunar globe, shining with a dingy coppery kind of light--'the ashen light,' as it is called. People talk of this as 'the old moon in the young moon's arms,' and weather-wise (or foolish) individuals pronounce it to be a sign of bad weather. It is, of course, nothing of the sort, for it can be seen every month when the sky is reasonably clear; but it is the sign that our world shines to the other worlds of space as they do to her; for this dim light upon the part of the moon unlit by the sun is simply the light which our own world reflects from her surface to the moon. In amount it is thirteen times more than that which the moon gives to us, as the earth presents to her satellite a disc thirteen times as large as that exhibited by the latter.