"A few years ago, when christening celestial formations was more in fashion than it is now, a man simply had to use a telescope for an evening or two on Mars or the moon, and spice the relation of his seeings with something in the way of novelty, when his name would be pretty certainly attached to an object and hung in the heavens for all time! A writer in the _Astronomical Register_ for January, 1879, humorously suggested that 'the matter should be put into the hands of an advertising agent,' and 'made the means of raising a revenue for astronomical purposes.' Some men would not object to pay handsomely for the distinction of having their names applied to the seas and continents of Mars or the craters of the moon." An occultation of Mars by the moon is recorded by Aristotle as having occurred on April 4, 357 B.C.[113] Seen from Mars the maximum apparent distance between the earth and moon would vary from 3½' to nearly 17'.[114] CHAPTER VII The Minor Planets Up to 1908 the number of minor planets (or asteroids) certainly known amounted to over 650. From an examination of the distribution of the first 512 of these small bodies, Dr. P. Stroobant finds that a decided maximum in number occurs between the limits of distance of 2·55 and 2·85 (earth's mean distance from sun = 1), "199 of the asteroids considered revolving in this annulus." He finds that nearly all the asteroidal matter is concentrated near to the middle of the ring in the neighbourhood of the mean distance of 2·7, and the smallest asteroids are relatively less numerous in the richest zones.[115] There are some "striking similarities" in the orbits of some of the asteroids. Thus, in the small planets Sophia (No. 251 in order of discovery) and Magdalena (No. 318) we have the mean distance of Sophia 3·10, and that of Magdalena 3·19 (earth's mean distance = 1). The eccentricities of the orbits are 0·09 and 0·07; and the inclinations of the orbits to the plane of the ecliptic 10° 29' and 10° 33' respectively.[116] This similarity may be--and probably is--merely accidental, but it is none the less curious and interesting. Some very interesting discoveries have recently been made among the minor planets. The orbit of Eros intersects the orbit of Mars; and the following have nearly the same mean distance from the sun as Jupiter:-- Achilles (1906 TG), No. 588, Patrocles (1906 XY), No. 617, Hector (1907 XM), No. 624, and another (No. 659) has been recently found. Each of these small planets "moves approximately in a vertex of an equilateral triangle that it forms with Jupiter and the sun."[117] The minor planet known provisionally as HN is remarkable for the large eccentricity of its orbit (0·38), and its small perihelion distance (1·6). When discovered it had a very high South Declination (61½°), showing that the inclination of the plane of its orbit to the plane of the ecliptic is considerable.[118]