THE MINOR PLANETS.

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amongst those with which we are acquainted, owing to thepaucity of their numbers compared with the vastuess of thespace through which they are scattered. But if there reallybe millions too small for us to detect, such aggregation maystill be going on with greater frequency.

It will, however, be noticed, that we have not, thus far,in suggesting such an origin for these bodies, in any wiseaccounted for the exceptional inclination of a considerablenumber of their orbits to the plane of the ecliptic. And wemay take this opportunity to remark that these inclinationsinvolve a special difficulty in connection with the process bywhich the planets are supposed to have been formed, in thegradual development of the Solar System according to Laplace’sNebular Hypothesis. He imagined that the various planetswere originated by rings thrown off from the equatoreal partsof a nebula, while it was rapidly revolving round a polar axis.But if such a ring, containing less matter than usual, had beenthus cast off, and had gradually formed the Minor Planets,we should have expected to find them all revolving in planesinclined at no great angle to that of the ecliptic, as is the casewith all the other planets. -

The considerable inclination of many of their orbits, therefore,leads us to one of two suppositions. It may be, according toa modification of the Nebular Hypothesis which lias beensuggested, that the successive portions of the original nebulawere separated, not as equatoreal rings, but as spheroidalenvelopes, which in most cases, after a while, gradually randown (if we may be allowed to use the expression), throughthe descent of their polar regions towards their equators, intothe form of rings, by the breaking up and aggregation of whichthe planets were formed. Upon this supposition, it mayperhaps have been possible for a considerable number of theMinor Planets to have been generated in various latitudes ofsuch an envelope, before it degenerated into the form of aring, the. result of which, in some way not very easy toconceive, might be that they would finally move in widelydiffering planes.

Or, on the other hand, we may imagine, that,, during the