Unfortunately, our comparative proximity to this beautiful planet does not much aid us in learning anything about her personal peculiarities. Shining only by reflected light, and being, like Mercury, situated nearer to the sun than the earth is, when she comes around to the same side of the sun on which we are, her unillumined side is turned toward us, and at the point of very closest approach she is absolutely invisible to the naked eye. Through a telescope, however, she can be seen up to the very point of inferior conjunction. What we see then is a mere curved line of light, so thin is the crescent she presents; but it is always apparent except when the planet makes a transit. During a transit she is actually in our line of sight with the bright disc of the sun, and is neither above nor below it, as at the ordinary times of inferior conjunction. The slender crescent that we ordinarily see offers a very narrow field for observation. If there is any one on Venus who is studying the earth, he has a much easier task than we have in our effort to learn something about her. The earth is not only somewhat larger than the planet, but when the two bodies are nearest together the disc of the earth is fully illuminated, and so must show a splendid face; and then, our atmosphere probably interferes less with close observation than that of Venus. This little terrestrial system would undoubtedly shine as a magnificent pair of stars if observed from Venus. At that distance our moon would appear considerably larger than Venus appears to us when at superior conjunction, the earth would seem much larger than Venus ever does to us, and the distance between them would seem to be a little more than the apparent diameter of the full moon as we see it. The light of the earth must cause much more of a shadow than we ever get from the light of Venus. It has been suggested that light from the earth is responsible for a dusky illumination of the dark side of Venus, which is occasionally seen, and which enables us to distinguish her entire outline even when only the merest line of a crescent is really illuminated. It is known to be earth-shine that causes what is apparently the same phenomenon often seen by us on the moon; but it seems that there is no reason to think that our earth, at its distance, would be sufficiently brilliant to illuminate Venus even so slightly. The cause of the illumination is not known; but it is thought that it may have some electrical origin, probably similar to that of our aurora.