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THE PLANET MARS.

refer to dates very near to the time of its Opposition. It may,however, he well to mention that this would not always he itsshape. Such a planet as Jupiter is so distant from the Earth that the change of phase by which its disc occasionallyappears to fall very slightly short of a complete circle is almosttoo small to be detected; while that of Saturn , or of anymore distant planet, is cpiite inappreciable; but Mars is,comparatively speaking, so near to us, that its change of phaseis at times very noticeable. It must, however, be rememberedthat, its orbit being exterior to our own, its phase does notvary from that which we see in a Full Moon to that whichbelongs to a New Moon , but only diminishes to some extentfrom a circular form, and then begins to increase again.When the planet is in Opposition to the Sun and at its nearestto the Earth , its illuminated disc is circular. When it is uponthe opposite side of the Sun, in Conjunction with it, and at itsgreatest distance from the Earth , it would (if visible) be alsocircular, although very much smaller in diameter. In inter-mediate positions one-half of its illuminated disc falls some-what short of a circular form, the diminution being greatestwhen the planet is in quadrature-— i.e., when it is seen in adirection at right angles to that of the Sun. It then presentsan appearance similar to that of the Moon when it is threedays from being full; one diameter being about -Sths of thelength of the other.

We must, however, hasten on to speak of various other veryinteresting questions connected with the physical condition ofMars , although the space at our disposal will only allow us toallude to them with the utmost possible brevity. Why, itmay be asked, is its light so red, that from ancient times ithas been associated with wars, and stratagems, and toils ; thatPropertius calls it “ the savage star of rapacious Mars ; ”and that Dante, as he describes the heaven of this planet,declares: —

“ With him shalt thou see,

That mortal who was at his birth imprestSo strongly with this star, that of his deedsThe nations shall take note ” 1