Young Folks' Library, Volume XI (of 20) eBook

paced of the two will have completed a revolution and a twelfth.  But were we to retard the motion of the latter, reducing it to only twice that of its companion, they would always meet at the figure twelve, as it would exactly complete two circuits while the hour hand was performing one.  Venus thus overtakes and passes the earth once in five hundred and eighty-four days, or nearly two and a half of her own years, constituting what is called her synodic period of apparent revolution as seen from this globe.  She thus presents to us all the phases undergone by our own satellite during a lunar month, passing from new to full, and vice versa, through the various intervening gradations of form.

The phases of Venus are amongst the most beautiful subjects for observation in a moderate telescope, as her silver bow, gradually brightening in the evening dusk, or fading in the dawn,

  “On a bed of daffodil sky,”

is, after the two greater luminaries that rule the day and night, the most brilliant object in the heavens.



The parallel between Venus and

  “That orbed maiden with fire laden,
   Whom mortals call the moon,”

is carried a stage further.  Most of us are familiar with the spectacle in which the Ancient Egyptians saw symbolized Horus on the lap of Isis, but which we more prosaically term “the old moon in the new moon’s arms.”  The strongly illuminated half circle next the sun is then seen embracing with its horns a dusky sphere, contrasting with it as tarnished silver does with the newly burnished metal.  The same phenomenon is occasionally, though very rarely, exhibited by Venus, while close to the sun at inferior injunction, when the shadowy form of the full orb is seen to shine dimly within her crescent with what is termed “the ashen light.”  More wonderful still, this “glimmering sphere” is then crowned, as with a silver halo, by a thin luminous arch, forming a secondary sickle facing the one nearest the sun, and doubtless due to the refraction of his rays round the globe of the planet, through the upper regions of her twilight atmosphere.  This spectacle was first observed by the Jesuit Ricciolo, an opponent of the Copernican theory, on January 9th, 1643.  He describes the planet as ruddy near the sun, yellowish in the middle, and of greenish blue on the side remote from the sun; while he also noted the bow of light limiting the dark hemisphere.  Scarcely daring to trust his own eyesight, he ascribed these appearances, although he recorded them, to illusory reflection in the telescope.


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