Professor Vogel, of Berlin, who himself saw part of the night-side of Venus, in its semi-obscurity in November, 1871, ascribed its visibility to a twilight effect caused by a very extensive atmosphere. The light thus transmitted to us by aerial diffusion and giving the ashen light, is reflected sunlight, while that sent by the luminous arc on its edge is direct sunlight, refracted, or bent round to us, from behind the planet. The silver selvedge of the dawn edging the dark limb may consequently be the brightest part of the broken nimbus that then seems to surround her. A similar appearance is observed during transits of Venus, when she passes directly between us and the actual solar disk. A silver thread is then seen encircling that side of the planet which has not yet entered on the face of the sun or "a shadowy nebulous ring," as it was described by Mr. Macdonnell at Eden, surrounds the whole planetary disk when two-thirds of it have passed the solar edge. As it moves off it, the same aureole again becomes visible, testifying to the existence of an atmosphere of considerable extent exterior to the sharply outlined surface ordinarily visible. The shimmering haze of reflected sunlight which perpetually enfolds her is only made apparent to us under exceptional circumstances which cut off some portion of her more immediate light, just as we see the motes in the air illuminated by a candle if we hide the actual flame from our eyes. The perennial twilight which seems to reign over the nocturnal hemisphere of Venus may compensate, perhaps, for the want of a satellite to modify its darkness. The great prolongation at other times of the horns of her crescent, so as to embrace almost her entire circumference with a tenuous ring of light, is doubtless due to the same cause, as their visibility should otherwise be limited to a half segment of a circle. The regions thus shining to us are obviously those on which the sun has not yet set, his appearance above the horizon being prolonged, as in our own case, by refraction, though to a much larger extent. The magnitude of the sun's disk as seen from Venus, a third larger than it appears to us, is also adducted by Mr. Proctor in his posthumous work, "The Old and the New Astronomy," edited and completed by Mr. A.C. Ranyard, as an element in extending the illumination of Venus to more than a hemisphere of her surface. As his diameter there is 44-1/4°, a zone of more than 22° wide outside the sunward hemisphere is he thinks illuminated by direct though partial sunlight, the orb being throughout this tract still partially above the horizon. [Illustration: GEOGRAPHICAL ASPECT OF VENUS.] [Illustration] THE STARS (FROM STARLAND.) BY SIR ROBERT S. BALL. [Illustration]