Such distances are amazing and almost terrifying to the imagination. The mind is bewildered and almost overwhelmed when attempting to form a conception of such portions of immensity, and feels its own littleness, the limited nature of its powers, and its utter incapacity for grasping the amplitudes of creation. But though it were possible for us to wing our flight to such a distant orb as 61 Cygni, we should still find ourselves standing only on the verge of the starry firmament where ten thousands of other orbs a thousand times more distant would meet our view. We have reason to believe that a space equal to that which we are now considering intervenes between most of the stars which diversify our nocturnal sky. The stars appear of different magnitudes; but we have the strongest reason to conclude that in the majority of instances this is owing, not to the difference of their real magnitudes, but to the different distances at which they are placed from our globe. If, then, the distance of a star of the first or second magnitude, or those which are nearest to us, be so immensely great, what must be the distance of stars of the sixteenth or twentieth magnitude, which can be distinguished only by the most powerful telescopes? Some of these must be many millions of times more distant than the nearest star whose distance now appears to be determined. And what shall we think of the distance of those which lie beyond the reach of any telescope that has yet been constructed, stretching beyond the utmost limits of mortal vision, within the unexplored regions of immensity? Here even the most vigorous imagination drops its wing, and owns itself utterly unable to penetrate this mysterious and boundless unknown. Turning now from the sun, whose distance was first measured, and from the nearest star with which we are acquainted, let us think about the most radiant star in the heavens--Sirius, “the blazing Dog-star of the ancients;” named by one astronomer “the king of suns.” First, as to the color of Sirius. He belongs to the order of “White Suns,” and among all the white suns known to us, Sirius ranks as chief. There may be many at greater distances far surpassing him in size, and weight, and brilliancy; but we can only speak so far as we know. Strange to say, Sirius was not always a “white sun;” for ancient writers describe him as being, in their days, a _red_ star. This change is very singular, and difficult to understand. But Sirius is not the only example of the kind. Many alterations in color have been noticed as taking place, often in a much shorter space of time. For instance, one star, which was a white sun in the days of Herschel, is now a golden sun.