Among multiple stars there are some very remarkable instances in Scorpio. β Scorpii is a pair of bright stars (easily separated with a 3-inch telescope) with a third fainter companion, and besides these, one of the bright components is a spectroscopic pair, and the whole company is travelling together through space. The joint mass of the spectroscopic pair is twenty-one times as great as that of our sun, and they revolve about one another in seven days; but a very strange feature is that _some_ lines in their joint spectrum, due to calcium gas, behave differently from the rest, and it is thought that these two revolving stars may be enveloped in a calcium cloud which travels with them. ξ Scorpii is a telescopic double which has been watched throughout a complete revolution of ninety-six years. It was discovered by Sir William Herschel in 1782. Here also there is a third star, much fainter and more distant than the brighter companion, and all are travelling together through space. ν Scorpii is one of the “double-doubles,” of which a good many are known, where a star that looks single to the naked eye is seen as a pair with a telescope, and each of these becomes a pair with higher powers. It has been described as “perhaps the most beautiful quadruple in the heavens.” Both pairs journey together through the skies. σ Orionis, the fourth-magnitude star just below Orion’s belt, separates very easily into two unequal components. Herschel found each of these to be triple, and called it a “double-treble.” Later it was found to be “double-quadruple,” with more stars between the two groups. In the same way the beautiful naked-eye double star α Capricorni is seen in good telescopes to consist of two groups of stars, one (α¹) triple, the other (α²) quadruple. If a group like this forms a connected system, the motions of the several stars must be highly complicated. VII THE ASTONISHING STAR, ETA ARGŪS