obliquity in the lines of direction in which the opposing currents met each other; that this motion would increase as the agglomeration proceeded; that at certain intervals the centrifugal force, acting on the remoter part of the rotating mass, would overcome the agglomerating force; and that a series of rings would thus be left apart, each possessing the motion proper to itself at the crisis of separation. These, again, would only continue in their annular form, if they were entirely uniform in their internal structure. There being many chances against this, they would probably break up in the first instance, and be thereafter "agglomerated into one or several masses, which would become representatives of the primary mass, and perhaps give rise to a progeny of inferior masses." In support of this theory, reference is made to the existence, at the present moment, of certain cloud-like nebulæ, or masses of diffused luminous matter, exhibiting a variety of appearances, as if they were in various degrees of condensation, and which are described as "solar systems in the process of being formed" out of a previous condition of matter. And the observations of M. Plateau, of Ghent, are adduced as affording an experimental verification of some parts of the theory, and, especially, as serving to explain the spherical form of the planets, the flattening at the poles, and the swelling out at the equator.
It does not belong to our proper province, nor is it necessary for our present purpose, to discuss the merits of this theory, considered as a question of science. This has been already done, with various degrees of ability, but with unwonted unanimity, by some of the ablest men of the age—by Whewell, Sedgwick and Mason, in England, by Sir David Brewster and Mr. Miller, in Scotland, and by Professor Dod and President Hitchcock, in America.[31] But, viewing it simply in its relation to the Theistic argument, we conceive that the adverse presumption which it may possibly generate in some minds against the evidence of Natural Theology, will be effectually neutralized by establishing the following positions:
That it is a mere hypothesis, and one which, from the very nature of the case, is incapable of being proved by such evidence as is necessary to establish a matter of fact.
That the progress of scientific discovery, so far from tending to verify and confirm, has served rather to disprove and invalidate the fundamental assumption on which it rests.
That even were it admitted, either as a possible, or probable, or certain explanation of the origin of the present planetary systems, it would not necessarily destroy the evidence of Theology, nor establish on its ruins the cause of Atheism.
Each of these positions may be conclusively established, and the three combined constitute a complete answer to the theory of Development, in so far as it has been applied in the support or defence of Atheism.
1. That it is a mere hypothesis or conjecture, designed, not to establish the historical fact, but to explain merely the dynamical possibility of the production of the planetary bodies by the operation of known natural laws, must be admitted, I think, even by its most enthusiastic admirers. It might have seemed, indeed, to have something like a basis of fact to rest upon, had the conception of the elder Herschell been verified, when he announced the existence of a nebulous fluid, capable of being distinguished, by certain well-defined marks, from unresolved clusters of stars; but even then it presupposed so many postulates, which could in no way be established by experimental or historical evidence, that it could scarcely be regarded in any other light than as an ingenious speculation or a splendid conjecture. For, let it be considered, first of all, that the theory proceeds on the assumption of the existence and wide diffusion of a nebulous fluid of whose reality there is no actual proof; secondly, that it necessarily requires, also, the supposed existence of certain favorable conditions; and, thirdly, the operation of certain invariable laws; and it will be manifest at once that it is purely hypothetical throughout, and that it includes a variety of topics which never have been, and never can be made the subjects of experimental verification. For it postulates, in the words of an acute writer, "the establishment of nuclei in the body of the elemental mass, as well as the action of heat on its substance, and then seeks to explain the concentration of the nebulous particles into these nuclei by the force of gravitation, the rotation of the bodies so produced by the confluence of the nebulous fluid, the separation of a portion of the outer surface of these revolving masses in the form of rings, the disruption of these rings, and the subsequent recomposition of their fragments into separate spheres, answering to the planets and satellites of our system."[32] But even were the existence of a nebulous fluid admitted, we have no access to know what was its internal structure; we cannot determine whether it was uniform and homogeneous throughout, or whether it contained nuclei which might become centres of aggregation; we have no means of estimating the intensity of the heat which belonged to it, or of calculating the process by which it was dispersed, so as to occasion the condensation of successive portions of the mass. No eye ever saw the separation of any part of it in the form of a ring, or the disruption of that ring, or the subsequent recomposition of its fragments into a solid sphere. And even had all this been matter, not of mere conjecture, but of actual observation, it would still have left much to be explained which can only be accounted for by ascribing it to a designing Intelligent Cause.
2. The progress of scientific discovery, so far from tending to verify, has served rather to invalidate the fundamental assumption on which the whole theory depends. That assumption was the existence of a Nebulous Fluid or Fire-Mist, capable of being distinguished, by certain characteristic marks, from unresolved nebulæ or clusters of stars. The existence of any such fluid has become more and more doubtful, in proportion as astronomers have been enabled, with the aid of larger and better constructed telescopes, to resolve several nebulæ which had previously defied the power of less perfect instruments. We do not affirm that every cluster has been already resolved, nor is it necessary for the purposes of our argument to suppose that, at any future time, this stupendous achievement is likely to be effected; for it is a very obvious consideration, that just in proportion as our telescopic powers are enlarged so as to enable us to resolve many of the nearer nebulæ, they must also bring within the range of our extended vision others more remote and hitherto unperceived, which may continue to exhibit the same cloud-like appearance as the former, until, by a new improvement of the telescope, we may succeed in separating them into distinct stars; and even then the march of discovery is not ended—we may reasonably expect that with every fresh increase of telescopic vision, new clusters will be brought into view, and new clouds appear in the utmost verge of the horizon. But, unquestionably, the progress which has already been made in this direction affords a strong presumption in favor of the idea, that the apparent nebulosity of those masses which still appear, even to our best telescopes, as cloud-like vapors, is to be ascribed rather to the imperfection of our instruments than to any difference between them and such as have been already resolved. Sir John Herschell, a high authority in such a case, tells us that "we have every reason to believe, at least in the generality of cases, that a nebula is nothing more than a cluster of stars."[33] Sir David Brewster is equally explicit: "It was certainly a rash generalization to maintain that nebulæ differed essentially from clusters of stars, because existing telescopes could not resolve them. The very first application of Lord Rosse's telescopes to the heavens overturned the hypothesis; and with such unequivocal facts as that instrument has brought to light, we regard it as a most unwarrantable assumption to suppose that there are in the heavenly spaces any masses of matter different from solid bodies, composing planetary systems."[34] And Professor Nichol, while he gracefully acknowledges that he has "somewhat altered the views which he formerly gave to the public, as the highest then known and generally entertained, regarding the structure of the heavens," states, as the result of more mature reflection, that "the supposed distribution of a self-luminous fluid, in separate patches, through the heavens, has, beyond all doubt, been proved fallacious by that most remarkable of telescopic achievements—the resolution of the great nebula in Orion into a superb cluster of stars; and that this discovery necessitates important changes in previous speculations on Cosmogony."[35]
In short, Lord Rosse's observations at Parsonstown have conclusively proved that what appeared to be a nebula was in reality a cluster of stars; and while they still leave many nebulæ unresolved, they afford a strong warrant for believing that discoveries in the same direction might be indefinitely extended
