and of those of them of which the orbits have been computed, no fewer than 23 have a mean distance exceeding 3 in terms of the Earth???s. It is evident from this how comparatively erratic are the fainter members of the extensive family with which we are dealing. (4) to ilhirate the next point, it may be noted that among the planetoids whose sizes have been approximately measured, the orbits of the two largest, Vesta and Ceres, have eccentricities falling between ??05 and ??10, whilst the orbits of the two smallest, Menippe and Eva, have eccentricities falling between ??20 and ??25, and between ??30 and ??35. And then among those more recently discovered, having diameters so small that measurement of them has not been practicable, come the extremely erratic ones,???Hilda and Thule, which have mean distances of 3??97 and 4??25 respectively; ??thra, having an orbit so eccentric that it cuts the orbit of Mars; and Medusa, which has the smallest mean distance from the Sun of any. (5) If the average eccentricities of the orbits of the planetoids grouped according to their decreasing sizes are compared, no very definite results are disclosed, excepting this, that the eight Polyhymnia, Atalanta, Eurydice, ??thra, Eva, Andromache, Istria, and Eudora, which have the greatest eccentricities (falling between ??30 and ??38), are all among those of smallest star-magnitudes. Nor when we consider the inclinations of the orbits do we meet with obvious verifications; since the proportion of highly-inclined orbits among the smaller planetoids does not appear to be greater than among the others. But consideration shows that there are two ways in which these last comparisons are vitiated. One is that the inclinations are measured from the plane of the ecliptic, instead of being measured from the plane of the orbit of the hypothetical planet. The other, and more important one, is that the search for planetoids hasnaturally been carried on in that comparatively narrow zone within which most of theirorbits fall; and that, consequently, those having the most highly-inclined orbits are the least likely to have been detected, especially if they are at the same time among the smallest. Moreover, considering the general relation between the inclination of planetoid orbits and their eccentricities, it is probable that among the orbits of these undetected planetoids are many of the most eccentric. But while recognizing the incompleteness of the evidence, it seems to me that it goes far to justify the hypothesis of Olbers, and is quite incongruous with that of Laplace. And as having the same meanings let me not omit the remarkable fact concerning the planetoidsdiscovered by D???Arrest, that ???if theirorbits are figured under the form of material rings, these rings will be found so entangled, that it would be possible, by means of one among them taken at hazard, to lift up all the rest,??????a fact incongruouswith Laplace???s hypothesis, which implies an approximate concentricity, but quite congruous with the hypothesisof an

exploded planet. Next to be considered come phenomena, the bearings of which on the question before us are scarcely considered???I mean those presented by meteors and shooting stars. The natures and distributions ofthese harmonize with the hypothesis of anexploded planet, and I think with no other hypothesis. The theory of volcanic origin, joined with the remark that the Sun emits jets which might propel them with adequate velocities, seems quite untenable. .