One of the finest and loftiest flights of Longfellow's imagination is to be found in his poem on the occultation of Orion. He has seldom, if ever, sounded a more vigorous strain. After alluding to that music of the spheres which Pythagoras dreamed of, and which Shakespeare has described in a passage of great beauty, he continues:-- "Beneath the sky's triumphal arch This music sounded like a march, And with its chorus seemed to be Preluding some great tragedy. Sirius was rising in the east; And, slow ascending one by one, The kindling constellations shone. Begirt with many a blazing star, Stood the great giant Algebar, Orion, hunter of the beast! His sword hung gleaming by his side; And, on his arm, the lion's hide Scattered across the midnight air The golden radiance of its hair." The most ancient observer who wished, with his own eyes, to assure himself whether the number of the stars was infinite, must have quickly perceived that, in spite of an apparent impossibility, it is no difficult task to complete their enumeration. To execute this operation conveniently, however, we must invent a process; and of all processes, the simplest, and that which first occurs to the mind, is to group the stars by configurations which, to a certain degree, are _mnemo-technical_. Such, in our belief, is the true origin--a point so often and laboriously discussed--of the _asterisms_ or _constellations_. Their fanciful, mythological, or poetical embellishments, are of later date. * * * * * The census or enumeration of the stars, which we suppose to have commenced during our winter nights, must at first have been limited to the most characteristic groups, composed of the most brilliant points. In this scientific labour the first rank would necessarily be occupied by Arctos (or Ursa Major) and Orion. Why? Because these two constellations attract and rivet everybody's gaze. [Illustration: FIG. 3.--Orion.] Orion is situated on the side opposite to the Great Bear. It is the most beautiful constellation in our western sky. You may easily recognise it by three stars, very close together, which are inscribed, as it were, in the centre of a great trapezium of four stars, two of which are of the first magnitude. Beneath the three first stars, called the Three Kings, or Orion's Belt, is visible a small stellar group of the fourth and fifth magnitude, near which, with a good average glass, may be distinguished the largest and most remarkable of the nebulæ. Here we find the mythologists--those theologians of the Greco-Roman polytheism--at disagreement. According to an ancient legend, immortalised by Homer-- "Aurora sought Orion's love,... Till, in Ortygia, Dian's wingèd dart Had pierced the hapless hunter to the heart."[3] The giant, in the lower world, is still animated by a burning passion for the chase--