NEBITLE, a name given to indistinct patches of light in the beaven§, supposed to proceed from aggregations of rarely distributed matter belonging to distant worlds in the course of formation. By the gradual improvement of telescopes in power and distinct ness, these nebulae have, one after another, become resolved into clusters of distinct stars, and it is now generally supposed that such a resolution of all nebulae which have been observed is only limited by the power of the telescope. It is probable that the, group of stars with which our system is immediately surrounded, zi.tal which fags to our eyes the galaxy which studs the firmament., would, if looked upon from the immeas urable distances at which the so-called nebula are situated, itself assume the appearance of such a nebula; and that in the intervals there exist spaces as void of starry worlds as these are comparatively full of them. Sec &rills. Some nebuke are of a round form presenting a gradual condensation towards the center; others consist of one star sur rounded by a nebulous haze; while a third class present just the, stone appearance as would he exhibited by the solar system, if seen front a point immensely distant. These
and other phenomena suggested to Laplace the idea, afterwards developed into a theory, and known as the nebular hypothesis, that these nebulae were systems in process of for mation; the first stage presenting an agglomeration of nebulous matter of uniform density, which, in the second stage, showed a tendency to gradual condensation towards the center: and, finally, the nebulous matter round the now-formed center of the system, separated itself into distinct portions, each portion becoming condensed into a planet. The same opinion regarding the formation of planets from nebula) was put forward by sir William Herschel in 1811; but the subsequent discoveries made by lord Bosse, were supposed to expose a fallacy in this theory. That wonderful instrument, the spectro scope, has, however, recently reinstated the nebular theory, by showing that among these appearanecs, there are real nebulae devoid of solid or liquid matter, and consisting of masses of glowing gas—apparently nitrogen and hydrogen.