Ancient poets said that once there were seven Pleiads, but one wept itself out at the fall of the city of Troy. That is a pretty fancy; but if one of those so distant stars had gone out when Troy fell, its light might yet be shining for us, and certainly would have shone on Ovid, who told the tale. A poet has written truly:-- “Were a star quenched on high, For ages would its light Still travelling downward through the sky, Fall on our mortal sight.” So vast are these star-distances that it takes hundreds of years for the light of a star to reach us, and yet light moves one hundred and eighty-six thousand miles a second! This is much faster than Puck, who could “put a girdle roundabout the earth in forty minutes!” What an immensity is this about us! All that void amid the starry systems we call stellar or inter-stellar space. Lit by so many splendid suns, is it not then glowing with the light of high noon a million times multiplied? No. The higher we rise above the earth, the darker becomes the color of the sky, until it hangs like a pall of unspeakable blackness. Why is this? Why is light not light? Why this absolute darkness among so many, many suns? It is simply lack of dust! There must be something to throw back and scatter the rays of light before it can be visible. Unless far up in stellar space there is dust, star-dust, a whirl of motes or stones to seize and throw back the light, then all must be very dark. Here on our own little globe the glorious sunbeams lighten us, thanks to dust in our atmosphere. The sunshine reveals to us the dust, but the dust makes the sunshine visible. Sunbeams and dust, each one invisible without the other! FOOTNOTES: [16] This, of course, is merely a conjecture, which it would need ages of observation to confirm. LESSON VII. A FRAGMENT OF THE MILKY WAY. “And now the still stars make all heaven sightly. One, in the low west, like the sky ablaze; The Swan, that with her shining Cross floats nightly, And Bears that slowly walk along their ways. There is the golden Lyre, and there the crown of fire: Thank God for nights so fair to these bright days.” --LOWELL, _Summer Nightfall_.