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 us to assert that the apparent contiguity is indeed a real contiguity. Here the theory of probabilities will come to our aid and supply reliable information of the most convincing character.

The illustration I shall take is one connected with a famous object. The Great Nebula in Orion is known to be the most glorious body of its class that the heavens display. Seen through a powerful telescope, like that of Lord Rosse at Parsonstown, the appearance of this grand "light-stain" is of indescribable glory to one whose previous acquaintance with practical astronomy enables him to inform the picture before him with the knowledge necessary for its comprehension. It is a vast volume of bluish gaseous material with hues of infinite softness and delicacy. Here it presents luminous tracts which glow with an exquisite blue light; there it graduates off until it is impossible to say where the nebula ceases and the black sky begins. But from our present point of view I am only thinking of the nebula as the nimbus of glory which surrounds the marvellous multiple star known to astronomers as Theta Orionis.

This complex sidereal system consists of four bright stars quite close together, with at least two smaller ones which evidently belong to the same scheme. The whole sextuple group makes a spectacle unique in the heavens. Wherever Theta Orionis happened to be in the sky it must necessarily be known as the most elaborately composed of all multiple stars. But, as a matter of fact, we find the wonderful star apparently occupying the most imposing site in the Great Nebula, so that the latter serves as a splendid setting to the complex star. The appearance presented would, of course, be explained if it should