The stability of the mounting was intended to render the telescope suitable for a special work. This was the observation of 'minor planets.' On the first day of the present century the first of these little bodies was discovered by Piazzi at Palermo. Three more were discovered at no great interval afterwards, and then there was an interval of thirty-eight years without any addition to their number. But from December 8, 1845, up to the present time, the work of picking up fresh individuals of these 'pocket planets' has gone on without interruption, until now more than 400 are known. Most of these are of no interest to us, but a few come sufficiently near to the earth for their distance to be very accurately determined; and when the distance of one member of the solar system is determined, those of all the others can be calculated from the relations which the law of gravitation reveals to us. It is a matter of importance, therefore, to continue the work of discovery, since we may at any time come across an interesting or useful member of the family; and that we may be able to distinguish between minor planets already discovered and new ones, their orbits must be determined as they are discovered, and some sort of watch kept on their movements. A striking example of the scientific prizes which we may light upon in the process of the rather dreary and most laborious work which the minor planets cause, has been recently supplied by the discovery of Eros. On August 13, 1898, Herr Witt, of the Urania Observatory, Berlin, discovered a very small planet that was moving much faster in the sky than is common with these small bodies. The great majority are very much farther from the sun than the planet Mars, many of them twice as far, and hence, since the time of a planet's revolution round the sun increases, in accordance with Kepler's law, more rapidly than does its distance, it follows that they move much more slowly than Mars. But this new object was moving at almost the same speed as Mars; it must, therefore, be most unusually near to us. Further observations soon proved that this was the case, and Eros, as the little stranger has been called, comes nearer to us than any other body of which we are aware except the moon. Venus when in transit is 24-1/2 millions of miles from us, Mars at its nearest is 34-1/2 millions, Eros at its nearest approach is but little over 13 millions.