Isaiah describes the Lord as "He that sitteth upon the circle of the earth, . . . that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in." And many others of the prophets use the same simile of a curtain which we have seen to be so appropriate to the appearance of the starry sky. Nowhere, however, have we any indication whether or not they considered the stars were all set _on_ this curtain, that is to say were all at the same distance from us. We now know that they are not equidistant from us, but this we largely base on the fact that the stars are of very different orders of brightness, and we judge that, on an average, the fainter a star appears, the further is it distant from us. To the Hebrews, as to us, it was evident that the stars differ in magnitude, and the writer of the Epistle to the Corinthians expressed this when he wrote-- "There is one glory of the sun, and another glory of the moon, and another glory of the stars: for one star differeth from another star in glory." The ancient Greek astronomers divided the stars according to their brightness into six classes, or six "magnitudes," to use the modern technical term. The average star of any particular magnitude gives about two and a half times as much light as the average star of the next magnitude. More exactly, the average first magnitude star gives one hundred times the light of the average star of the sixth magnitude. In a few instances we have been able to measure, in the very roughest degree, the distances of stars; not a hundred stars have their parallaxes known, and these have all been measured in the course of the last century. And so far away are these stars, even the nearest of them, that we do not express their distance from us in millions of miles; we express it in the time that their light takes in travelling from them to us. Now it takes light only one second to traverse 186,300 miles, and yet it requires four and a third years for the light from the nearest star to reach us. This is a star of the first magnitude, Alpha in the constellation of the Centaur. The next nearest star is a faint one of between the seventh and eighth magnitudes, and its light takes seven years to come. From a sixth magnitude star in the constellation of the Swan, the light requires eight years; and from Sirius, the brightest star in the heavens, light requires eight and a half years. These four stars are the nearest to us; from no other star, that we know of, does light take less than ten years to travel; from the majority of those whose distance we have succeeded in measuring, the light takes at least twenty years.