This little body was thus near us in 1894; but we did not then know this, for Eros was not discovered until 1898. After its discovery, however, it was traced back on many photographic plates, and the fact that it had been in our neighborhood was learned. For untold ages it has been making these visits to us every thirty-seven years, and we have known nothing of them. Its next near approach will be in 1931, and it will continue to come thereafter every thirty-seven years. Now that we know about them, these visits are not only pleasant to contemplate, but it is expected that when they occur the planetoid will be of great scientific value to us in helping to determine more surely and accurately the exact distance of the sun. The planetoids, though so minute and of no value as a spectacle, have been, and still are, very useful little bodies to us in a scientific way. In addition to furnishing an easy means of measuring the distance of the sun, they promise to throw some light on various questions of physics in which the planets, too, are involved. The brilliancy of Vesta, for instance, which has been mentioned, and the unaccountable variability in the brightness of some others of them have yet to be adjusted to known physical laws. Even the extreme eccentricity of some of their orbits, and the large tilt of some of them to the ecliptic, may be suggestive in finally solving certain planetary problems, for these impish little bodies are far from conforming to the regular ways of the planets, and there is, of course, some mechanical reason for their apparent waywardness. XVIII CONCLUSION The great variety of beauty that the planets present to us is sufficient to keep us always interested in them, when once we have acquired an acquaintance with them. Rarely is there an evening when some one of them does not enhance the charm of the splendid spectacle of the sky in which all the heavenly bodies save the sun have a part. Their greater brilliancy often brings them into view before the stars have begun to glow in the evening, and prolongs our sight of them after the rays of the sun have blotted out the light of the stars in the morning. Thus they are always single in their loveliness, and always hold a distinguished place in the midst of the brilliant company of the stars. Having considered these brilliant bodies individually and in detail, as we have, we ought by this time to be able to identify any one of them that shows itself in the evening sky, and to have a pretty fair notion of the general character and peculiarities of each. But even if one does not much care for detailed information concerning them, or, before seeking that, prefers first to become familiar with their appearance, a quick and sure recognition of them may be had by noting their positions and their very striking individual aspects as set forth in the preceding chapters.