Venus can never be seen away from the sun.

them, like the sun and moon. To-n near one star, to-morrow its position changed, and the next day a further d observed. Unlike the sun and moon, ho

moon move.

shifting star does not roll majestically round the heavens in one direction. It moves slightly towards the east, then stops for a few days, as if undecided as to the proper course to take, goes towards the west, again "halts between two opinions," and eventually determines to move eastward, after which the vacillations are repeated. But though the star moves towards the west at times, it shows a decided preference for the east, the swing eastwards being always greater than that westwards. In course of time, then, the Evening Star must make a circuit of the heavens. in the same direction as that in which the sun and What is more, the line of travel almost coincides with the ecliptic-with the path of the sun. When the relation of the Evening Star to the sun. is noticed, another strange variation is found. If observations are commenced when the star sets about three hours after the sun, it will soon be noticed that the difference between the two times of setting is gradually becoming less. From three hours the difference diminishes to two hours, to one hour, to half an hour, and eventually the star is lost in the sun's light, and we can follow it no longer. Shortly after this time, a "Morning Star" appears near the sun. The earliest Greeks knew this object by the name of Lucifer, the light-bearer. The distance between the star and the sun increases, and, as a consequence of this, the difference between the times of their risings increases also. When the star precedes the sun by about three hours, the limit is reached. It then begins to swing back towards our luminary until it is again lost to sight. A few weeks pass, and then an evening star is again seen very near the sun, and as time goes

on it swings out towards the east, setting longer and longer after the sun, until the previous difference of three hours is attained.

The first idea with regard to "morning" and "evening" stars would be that they were entirely different bodies. But when the birth of one had always been found to follow the death of the other, the speculation must have arisen as to whether the two stars were not one and the same object. This is really the case; Hesperus, the evening star, and Lucifer, the morning star, represent Venus seen under different circumstances.

In addition to Venus, there is another object which moves among the stars, now this way, now that way, now halting. Like the Evening Star, "the star of love and rest," this body travels round the zodiac in a series of loops. It swings from one side of the sun to the other, but does not get so far away as Venus. As a morning star, the Greeks knew the object by the name of Apollo. When it appeared in the evening its name was Mercury," the swift messenger of the gods." On account of the small swing on either side of the sun the two bodies never set long after one another. The greatest difference of time between the two risings or settings is less than two hours, and the average difference is about an hour. In our latitude Mercury is very rarely seen, but in Egypt, and other places where the skies are clear and the duration of twilight is short, he is a conspicuous object.

Venus and Mercury move among the stars, like the sun and moon. Three other bright objects were observed by the ancients to behave in the same peculiar manner. The date of the discovery of this

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motion is anterior to the time of which we possess any historic record. The cuneiform inscriptions of Babylonia and the hieroglyphics of Egypt show that the wandering stars" or or "planets" were familiarly known at least 2000 years before the commencement of our era, and no mention is made of the astronomers who first discriminated them from other celestial objects. Let us endeavour to trace the course of observations which would lead to their discovery.

Attention would be attracted to a star-like body which, though perhaps not brighter than other stars, differed from all of them in the fact that it did not twinkle appreciably. The object would be watched night after night, and would be found slowly to change its position on the celestial vault. These complicated motions must have perplexed early observers beyond measure, and only after records. of many years of observation had been mulated would it appear that they were governed by any law. Jupiter the brightest of the wan

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derers would be seen due south at midnight. then occupies the opposite point in the heavens to that in which the sun is at the time, and is therefore said to be in "opposition." As he moves slightly westward among the stars, the sun moves eastward through a much greater distance. And the time comes when Jupiter is seen in the west at sunset; is almost lost in the twilight glows; is drowned in sunlight. When this occurs, the planet and the sun rise together, south together, set together, the lesser light is assimilated by the greater, and the two bodies are said to be in "conjunction." A separation soon occurs. Jupiter becomes visible in the early morning,

Jupiter is observed near a star at a he will be found to the east of it opposition, and still farther east at one. It is only after eleven midnight the star and the planet are in the position.

Another planet known in prehisto named Saturn by the Greeks. His mov the stars is slow and almost impercept coloured planet is distinguished by the the god of war. This planet has apparently a very irregular movemen stars (Fig. 24).

Mercury and Venus can only be seen before sunrise or after sunset. They respect, therefore, from Jupiter, and Satu which are seen at all hours of the nig motions of all these bodies are characteri peculiarities. Each glides round the advancing in an eastward direction, then a little, and afterwards advancing to a po of the starting-point, to begin the perfor Each changes considerably in bright apparent size, Mars, Jupiter, and Saturn and brightest when in opposition. And tant fact of all, the planets are alway to the ecliptic.