Just east of the Harp Star, in the center of the Milky Way, rests a cross of stars, clear and bright, as if a cross had really been placed there and then studded with five big stars. During the month of May the Cross rises on its side (as viewed by an observer in the northern hemisphere), but it rests north and south as it reaches the zenith in midsummer. By December it has reached the slope in the west, and now assuming an upright position, descends majestically to the horizon. This descent is quite effective, especially at the moment when the pale orange star, which rests at its base, lightly touches a mountain range etched in the distance or the edge of a far-reaching plain. This 3rd magnitude star, Albireo, is a favorite with amateur astronomers, for it has a 5th magnitude companion star of the richest and most vivid greenish-blue. [Figure 71] This lovely double star with its sharply contrasted colors may be seen to good advantage in a small telescope and vies in beauty with the famous three-colored star, Gamma Andromedæ. Deneb, the brilliant white star at the head of the Cross, is a very distant sun but is so large that it shines forth brightly among our finest stars. It is estimated by astronomers as being at a much greater distance than the Harp Star, Vega, and Vega is distant about 232 millions of millions of miles! In contrast to the huge sun that Deneb must be to shine so brightly at its great distance, there is a little star above the armpiece on the eastern side of the Cross, which is the nearest star to the earth that has yet been found, as seen from the northern hemisphere. [Figure 72] This faint star is really a very tiny sun for nine more similar suns thrown into it and blazing as one big fire, would no more than equal our sun in brilliancy. In the vicinity of 61 Cygni, is a large, mysterious, black spot visible on account of the glow of light from the densely packed stars of the Milky Way. This spot was first described as being "like a hole" and was curiously named "A Sack of Coals." Science later suggested that since we have dark suns perhaps we also have dark nebulæ and that such an object may be lying between us and those distant stars. The late E. E. Barnard of Yerkes Observatory made extensive studies of the distribution of nebular matter and he seems to have definitely proved the existence of "dark nebulæ." The black spots and "rifts" in the Milky Way are now generally accepted to be dark nebulous matter which cuts out the light from the stellar regions behind them. Professor Barnard made many wonderful photographs of such dark spots and compiled a famous Catalogue of 182 Dark Markings in the sky. Dr. Hubble of the Mount Wilson Observatory found that in its normal state a nebula is dark rather than luminous. If a nebula shines it is because it is either illuminated by the light from the stars near it or because it is electrically excited in some way not clearly understood.