Arcturus is sometimes referred to under the name of _Arctophilax_, the “Bear-driver,” a name properly belonging to the constellation Boötes. In modern astronomical history it will always be memorable for the passage over it of the celebrated Comet of 1858, Donati’s Comet. At one time the star was almost involved in the head of the great comet, and yet it shone through the obstructing vapors with virtually undiminished lustre. It was a spectacle, said Professor Nichol, the like of which no one might see again though he should spend on earth fifty lives. At the beginning the comet was a little plume of fire, “shaped like a bird of paradise,” but it soon brightened into a stupendous scimetar, brandished in the sunset, and when it swept over Arcturus the whole astronomical world was watching to see what would happen to the star. Among the other stars of Boötes, Epsilon (ε) is specially worthy of notice, being a remarkable binary of finely contrasted colors, orange and sea-green. The distance is 2″.25, and the period of revolution long but undetermined. Struve called this star “Pulcherrima,” on account of its exceeding beauty. Although Arcturus by its splendor belittles the rest of the constellation, yet it requires no difficult exercise of the imagination to see a giant form there, towering behind the Bear, and urging on his dogs in the chase. The dogs are represented by Canes Venatici, of the beauty of whose chief star, Cor Caroli, I have spoken in the preceding chapter. In the upper part of Canes Venatici, about 3° southwest of Benetnasch, is the celebrated “Whirlpool Nebula” of Lord Rosse, which modern photographs show in a form so suggestive of tremendous disruptive forces that cosmogonists are at a loss to explain it. We now drop down to Libra, the “Balance,” which lies just west of Scorpio and east of Virgo. There is evidence that this constellation originally represented the outstretched claws of the Scorpion. Yet as an independent constellation it is very ancient. It has only two stars of any considerable magnitude, Alpha (α) and Beta (β). The former must have faded, for it is now the fainter. It lies almost on the ecliptic. These stars are interesting on account of their curious names, which themselves tend to prove that Libra once formed a part of Scorpio. Alpha is Zubenelgenubi, the “Southern Claw,” and Beta Zubeneschemali, the “Northern Claw.” These titles, as Allen shows, have been derived through the Arabic from the Greek names current in the time of Ptolemy. The first is yellowish-white, and the second pale green. Any good eye detects the difference of color at a glance, although the stars are about ten degrees apart. Zubenelgenubi is widely double, separable with an opera-glass.