It is the less necessary, however, to enter on a detailed exposition of his argument, because he admits that it can afford at the utmost only a probable proof of an hypothesis; and further, because it is expressly limited to the production of the planets and their satellites, while not only is the existence of the solar atmosphere presupposed, but also its existence in _a certain state_, and with _several determinate conditions_; while no account whatever is given of the origin either of the sun or its atmosphere, and none of the laws or conditions on which the whole process of development is confessedly dependent.
But the author of "The Vestiges" takes a much wider range, and attempts a more arduous task.

He seeks to account for the origin both of suns and of solar systems by the agency of natural laws.

Not content with the more limited form of the theory, which M.Comte holds to be the only legitimate or practical object of scientific treatment, he holds that the origin of the sun itself, and the _forms_, the _positions_, the _relations_, and the _motions_, of all the heavenly bodies, may be accounted for by supposing a previous state of matter, fluid or gasiform, subject only to the law of gravitation.

The Nebular Cosmogony, which is well characterized by himself as his "version of _the romance of Nature_," is based on the assumption that "the nebulous matter of space, previously to the formation of stellar and planetary bodies, must have been a universal FIRE-MIST,"[30] in other words, a diffused luminous vapor, intensely hot, which might be gradually condensed into a fluid, and then into a solid state, by losing less or more of its heat.
The existence of such a luminous matter being assumed, and it being further supposed that it was not entirely uniform or homogeneous, but that it existed in various states of condensation, and that it had "certain nuclei established in it which might become centres of aggregation for the neighboring diffused matter,"-- the author attempts to show that on such centres a rotatory motion would be established wherever, as was the most likely case, there was any 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.