Procyon is especially interesting because it is attended by an invisible star, which, while it has escaped all efforts to detect it with powerful telescopes, nevertheless reveals its presence by the effect of its attraction upon Procyon. It is a curious fact that both of the so-called Dog-Stars are thus attended by obscure or dusky companion-stars, which, notwithstanding their lack of luminosity, are of great magnitude. In the case of Sirius, the improvement in telescopes has brought the mysterious attendant into view, but Procyon's mate remains hidden from our eyes. But it can not escape the ken of the mathematician, whose penetrating mental vision has, in more than one instance, outstripped the discoveries of the telescope. Almost half a century ago the famous Bessel announced his conclusion--in the light of later developments it may well be called discovery--that both Sirius and Procyon were binary systems, consisting each of a visible and an invisible star. He calculated the probable period of revolution, and found it to be, in each case, approximately fifty years. Sixteen years after Bessel's death, one of Alvan Clark's unrivaled telescopes at last revealed the strange companion of Sirius, a huge body, half as massive as the giant Dog-Star itself, but ten thousand times less brilliant, and more recent observations have shown that its period of revolution is within six or seven months of the fifty years assigned by Bessel. If some of the enormous telescopes that have been constructed in the past few years should succeed in rendering Procyon's companion visible also, it is highly probable that Bessel's prediction would receive another substantial fulfillment. The mythological history of Canis Minor is somewhat obscure. According to various accounts it represents one of Diana's hunting-dogs, one of Orion's hounds, the Egyptian dog-headed god Anubis, and one of the dogs that devoured their master Actaeon after Diana had turned him into a stag. The mystical Dr. Seiss leaves all the ancient myth-makers far in the rear, and advances a very curious theory of his own about this constellation, in his "Gospel in the Stars," which is worth quoting as an example of the grotesque fancies that even in our day sometimes possess the minds of men when they venture beyond the safe confines of this terraqueous globe. After summarizing the various myths we have mentioned, he proceeds to identify Procyon, putting the name of the chief star for the constellation, "as the starry symbol of those heavenly armies which came forth along with the King of kings and Lord of lords to the battle of the great day of God Almighty, to make an end of misrule and usurpation on earth, and clear it of all the wild beasts which have been devastating it for these many ages." The reader will wonder all the more at this rhapsody after he has succeeded in picking out the modest Little Dog in the sky.