Fig. 583.—CHART OF MARS (Names according to Proctor and Green).
A Peer Continent. B Herschel Continent. C Fontana Land. D Secchi Continent, East. E Secchi Continent, Central. F Secchi Continent, West. G Mädler Continent. H Leverrier Land. 1 Herschel Strait. 2 Dawes Ocean. 3 Maraldi Sea. 4 Oudemans Sea. 5 Trouvelot Bay. 6 Funchal Bay. 7 Campani Sea. 8 De la Rue Ocean.
The Moons of Mars.
We must devote a few lines to the satellites of Mars, which during the last four years have proved a very interesting study for the astronomers, and some very interesting facts have been ascertained concerning the ruddy planet, which is now proved not to be “moonless Mars,” as the poet declared.
There are two satellites, which, in consequence of their distance from him, being so different, vary in apparent size. The outer one is twelve thousand, the inner one about three thousand five hundred miles from the planet, so the former would revolve in about thirty hours in a direction from west to east, and the inner moon goes round in the same way in about seven hours and a half. Mars revolves in twenty-four and a half hours from west to east. So the outer moon rises for him in the east, and the inner one in the west. This is accounted for by the fact that one travelling slower than Mars rises in the east, the other outruns him, and comes up in the west.
But if we suppose ourselves upon Mars we shall find that, after all, we have only one moon properly so called. The outer satellite is very small and very far away, so it is useless to give light—at most, it is no bigger than Mars appears to us on earth. So the Martians do not see two moons passing each other in the sky—that is, unless their eyes are of greater range and power than ours. Thus they have one moon rising in the west, appearing in all its phases every night, while our moon takes twenty-eight days to pass through her phases; for we must remember that Mars’ moon takes only seven hours and forty minutes to pass through its orbit, and therefore each quarter will not occupy quite two hours.
The Minor Planets, or Asteroids.
Passing onward from Mars towards Jupiter we arrive at a number of smaller planets, which will not concern us very much, as they are very small and scarcely visible without a good telescope. But a very interesting chapter in the history of astronomy was commenced when the discovery of these bodies was begun. In old times astronomers noticed a very considerable gap between Mars and Jupiter, which was remarkable when the regular progression of the distances between the planets was remembered. So Kepler was of opinion that some planet would be discovered having its orbit in that space between Mars and Jupiter. It is, however, to Piazzi, the Italian, that the discovery of the zone of asteroids is due.
Dec. 8th. Dec. 9th.
