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phiin lj miles off for Neptune, the most distant planet yet known. Extending this scheme, we should find that the aphelion distance of Encke's comet would

Fig. 16.

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be at 880 feet; the aphelion distance of DoDati's comet of 1858 at 6 miles; and the nearest fixed star at 7,500 miles.

According to this scale, the daily motion of Vulcan in its orbit would be 4| ieet; of Mercury, 3 feet; of Venus, 2 feet; of the Earth, If feet; of Mars, lj feet; of Jupiter, 10^ inches; of Saturn, 7ij inches; of Uranus, 5 inches; and of Neptune, 4 inches. This illustrates the fact that the orbital velocity of a planet decreases as its distance from the sun increases.

Conjunctions Of Planets.—The grouping together of two or more planets within a limited area of the heavens is a rare event. The earliest record we have is the one of Chinese origin, already mentioned on page 16, wherein it is stated that a conjunction of Mars, Jupiter, Saturn, and Mercury occurred in the

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VBNTTS AND JUPITER IN CONJUNCTION, JANUARY 30, 1868.

reign of the Emperor Chuenhio. Astronomers tell us that this actually took place Feb. 28, 2446 B. c, and that they were between 10° and 18° of Pisces. This was before the Deluge, so that the fact must

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have been afterward calculated and chronicled in their records. In 1859, Venus and Jupiter came so near each other that they appeared to the naked eye as one object. In 1725, Venus, Mercury, Jupiter, and Mars appeared in the same field of the telescope.

Are The Planets Inhabited?—This question is one which very naturally arises, when we think of the planets as worlds in so many respects similar to our own. We can give no satisfactory answer. Many think that the only object God can possibly have in making any world is to form an abode for man. Our own earth was evidently fitted up, although perhaps not created, for this express purpose. Everywhere about us we find proofs of special forethought and adaptation. Coal and oil in the earth for fuel and light, forests for timber, metals in the mountains for machinery, rivers for navigation, and level plains for corn. Our own bodies, the air, light, and heat are all fitted to each other with exquisite nicety. When we turn to the planets, we do not know but God has other races of intelligent beings who inhabit them, or even entirely different ends to attain. Of this, however, we are assured, that, if inhabited, the conditions on which life is supported vary much from those familiar to us. We shall notice these more especially as we speak of the different planets. We shall see (1) how they differ in light and heat, from seven times our usual temperature to less than 1010ft; (2) in the intensity of the force of gravity, from 1\ times that of the earth to less than ;(3) in the constitution of the planet itself, from a density | heavier than that of the earth to one nearly that of cork. The temperature sweeps downward through a scale of over

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2,000°in passing from Mercury to Uranus. No human being could reside on the former, while we cannot conceive of any polar inhabitant who could endure the intense cold of the latter. At the sun, one of our pounds would weigh 27 pounds; on our moon the pound weight would become only about 2 ounces; while on Vesta, one of the planetoids, a man could easily spring sixty feet in the air and sustain no shock. Yet while we speak of these peculiarities, we do not know what modification oi the atmosphere or physical features may exist even on Mercury to temper the heat, or on Uranus to reduce the cold. With, however, all these diversities, we must admit the power of an all-wise Creator to create beings adapted to the life and the land, however different from our own. The Power that prepared a world for us, could as easily and perfectly prepare one for other races. May it not be that the same love of diversity, which will not make two leaves after the same pattern nor two pebbles of the same size, delights in worlds peopled by races as diverse? While, then, we cannot affirm that the planets are inhabited, analogy would lead us to think that they are, and that the most distant star that shines in the arch of heaven is filled with living beings under the care and government of Him who enlivens the densest forest with the hum of insects, and populates even a drop of water with its teeming millions of animalculae.

Divisions Of The Planets.—The planets are divided into two classes: (1) Inferior, or those whose

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