Nearly fifty years later, that is to say, in our own time, another important planetary discovery was made. One of the recent additions to the numerous and constantly increasing family of the asteroids, a tiny body brought to light in 1898, turned out after all not to be circulating in the customary space between Mars and Jupiter, but actually in that between our earth and Mars. This body is very small, not more than about twenty miles across. It has received the name of Eros (the Greek equivalent for Cupid), in allusion to its insignificant size as compared with the other leading members of the system. This completes the list of the planets which, so far, have revealed themselves to us. Whether others exist time alone will show. Two or three have been suspected to revolve beyond the path of Neptune; and it has even been asserted, on more than one occasion, that a planet circulates nearer to the sun than Mercury. This supposed body, to which the name of "Vulcan" was provisionally given, is said to have been "discovered" in 1859 by a French doctor named Lescarbault, of Orgères near Orleans; but up to the present there has been no sufficient evidence of its existence. The reason why such uncertainty should exist upon this point is easy enough to understand, when we consider the overpowering glare which fills our atmosphere all around the sun's place in the sky. Mercury, the nearest known planet to the sun, is for this reason always very difficult to see; and even when, in its course, it gets sufficiently far from the sun to be left for a short time above the horizon after sunset, it is by no means an easy object to observe on account of the mists which usually hang about low down near the earth. One opportunity, however, offers itself from time to time to solve the riddle of an "intra-Mercurial" planet, that is to say, of a planet which circulates within the path followed by Mercury. The opportunity in question is furnished by a total eclipse of the sun; for when, during an eclipse of that kind, the body of the moon for a few minutes entirely hides the sun's face, and the dazzling glare is thus completely cut off, astronomers are enabled to give an unimpeded, though all too hurried, search to the region close around. A goodly number of total eclipses of the sun have, however, come and gone since the days of Lescarbault, and no planet, so far, has revealed itself in the intra-Mercurial space. It seems, therefore, quite safe to affirm that no globe of sufficient size to be seen by means of our modern telescopes circulates nearer to the sun than the planet Mercury. Next in importance to the planets, as permanent members of the solar system, come the relatively small and secondary bodies known by the name of Satellites. The name _satellite_ is derived from a Latin word signifying _an attendant_; for the bodies so-called move along always in close proximity to their respective "primaries," as the planets which they accompany are technically termed.