irregularities, nothing that is permanent, or can injure, either the planet, or its inhabitants, can take place. What were the means necessary to produce a result so astonishing? It was indispensable, that the force of attraction should diminish, as the square of the distance of bodies increases, that the masses of the revolving bodies should be small, compared with that of the body at the centre; that the orbits should not be much inclined to one another, and that their eccentricities should be but little. I think I understand the importance of these rules, unless it be the first. To explain that, suppose, that, instead of the power of attraction diminishing by distance, it had increased: think then of the planet Saturn, so large and so remote, "endued with the power of pulling the harder, from its being the further off." The result must have been, that it would have dragged in the course of years, our globe, or some of its sister planets, out of their courses, and have interfered with the order, and perplexed the motions, of our system. I quite understand now; will you tell me any thing more? Yes, one observation more, and then I have done this relates to the orbits of the planets. "The distance from the centre, at which a planet sets off, and the absolute force of attraction being fixed, the figure of its orbit depends upon two things the velocity with which the planet is projected, and the direction which it takes. And these, in order to produce a right result, must be within certain narrow limits. One, and only one velocity, united with one, and only one direction, will produce a perfect circle. And the velocity must be near to this velocity, and the direction also near to this direction, to produce orbits such as the planetary are, nearly circular, that is, ellipses with small eccentricities. The velocity and the direction must both be right. If the velocity is wrong, no correctness of direction will rectify the error; if the direction is in any considerable degree oblique, no velocity will produce the orbit required."—" Why then did the projectile velocity, and the projectile direction of the planets, happen to be nearly those, which retain them in a circular form? Why not one of the infinite number of the velocities, one of the infinite number of directions, which would make it approach much nearer to, or recede much further from, the sun?" I see, my dear mamma, the unavoidable conclusion; but you say, "nearly in a circular form:" do you mean to intimate, that there is a degree of velocity, or a line of direction, preferable to that imposed upon the earth, and the other planets? Would it, do you apprehend, be better for them to move in circular, than in elliptical orbits? No; that is not my conception of the matter: for, if "the system had retained in other respects its present constitution, though the planets had been at first sent round in exact circular orbits, they could not have kept them: and, if the law of attraction had not been what it is, every deviation would have been fatal: the planets once drawn, as drawn they necessarily must have been, out of their course, would have wandered in endless error." To what must we ascribe such obvious proofs and developements of "choice,"—" determination,"—" regulation," care, foresight, and benevolence? To the existence of a Being too wise to err. O! may the mysteries of Providence, intricate as the "mystic dance" of the planetary orbs, never weaken in your mind this conviction, much less shake the stability of your faith! END OF THE FIRST PART. |