There is reason to suspect that Newton looked at this question with a jaundiced eye. To do it justice, we must consider the planetary matter in a vortex, as the exponent of its motion, and not as originating or directing it. If planetary matter becomes involved in any vortex, it introduces the law of gravitation, which counteracts the expulsive force of the radial stream, and is thus enabled to retain its position in the centre. A predominating mass in the centre will, by its influence, retain other masses of matter at a distance from the centre, even when exposed to the full power of the radial stream. If the power of the central mass is harmoniously adjusted to the rotation of the vortex, (and the co-existence of the phenomena is itself the proof that such an adjustment does obtain,) the two principles will not clash or interfere with each other. Or in other words, that whatever might have been the initial condition of the solar vortex, the ultimate condition was necessarily one of equilibrium, or the system of the planets would not now exist. With this view of its constitution, we must consider that the periodic times of the planets approximately correspond to the times of the contiguous parts of the vortex. Consequently, in the solar vortex, the density of the ether is directly as the square roots of the distances from the axis. This is not the place fully to enter into a discussion of the question, or to show that the position of each planet in the system is due to the outstanding, uncompensated, portion of the expulsive force of the radial stream, modified by the density of the ether within the planets, and also by their own densities, diameters, inclinations of axis, and periods of rotation. That Jupiter could not remain in the orbit of Mercury, nor Mercury in that of Jupiter, by merely exchanging periods and distances, but that each planet can only be in equilibrio in its own orbit. That any change in the eccentricities of the planetary orbits will neither increase nor diminish the action of the radial stream of the vortex, and consequently will not interfere with the law of gravitation. In relation to the numerous questions that will spring up from such a position, it is sufficient here to say, that it is believed all objections can be satisfactorily answered; while, by this light, a long range of phenomena that have hitherto baffled the sagacity of the wise, come out plainly, and discover their parentage. In cometary astronomy we shall find much to substantiate these views. The anomalies in their motions, the discrepancies in their periods, calculated from different sets of observations, their nebulosities and appendages, will all receive a satisfactory solution; and these lawless wanderers of the deep be placed in a more interesting light. TEST OF A THEORY.