2. A group of four interior planets: Mercury, Venus, the Earth, and Mars. 3. A group of small planets, called asteroids, revolving beyond the orbit of Mars, and numbering, according to the latest discoveries, about two hundred and twenty. 4. A group of four planets beyond the asteroids: Jupiter, Saturn, Uranus, and Neptune. 5. The satellites of the planets, of which there are twenty now known; all but three of them belonging to the outer planets. 6. An intermediate number of bodies called comets and meteors, which revolve in very eccentric orbits. This system of bodies, constituting a mechanism by itself, apart from what are called the fixed stars, is the first object in nature to which our inquirer directs his studies. Inasmuch as the comets and meteors move in very eccentric orbits, and are supposed to come into our system from the illimitable spaces beyond it, although in the case of the comets, or some of them, mathematical calculations enable astronomers to predict their return when they have passed out of the solar system, and inasmuch as the sun and the superior planets may be contemplated as a grand piece of mechanism, and as the greatest mechanical object in nature of whose construction and movements we have some accurate knowledge, we will suppose that our inquirer confines his attention to this part of the solar system, without adverting to the action of the bodies which are not always, as these are, within the range of the telescope. One of the first things that would strike him would be the enormous range in the sizes, distances, and relative weights of these different bodies. He would learn, for example, that Neptune is eighty times as far from the sun as Mercury, and that Jupiter is several thousand times as heavy; and he would observe that these differences in magnitude, distance from the sun, and weight of each mass, are carried through a range of proportions stupendously great. If he followed the best lights of modern astronomy, he would learn that what is known, or accepted as known, in regard to the operation of any law among these bodies, is that they are bound together by the law of universal gravitation as a force to which all matter would be subjected when it should come to exist, in whatever forms it might be distributed; secondly, that when the bodies now composing the solar system should come into existence, the system would not owe its proportions to the operation of the law of gravitation, but would be the result of a plan so shaped as to admit of its being governed by the law of gravitation after the system had been made, in such a manner as to produce regularity and certainty of movement and to prevent dislocation and disturbance. What the great modern telescopes have enabled astronomers to discover tends very strongly to show that the plan of the solar system, in respect to the relative distances, magnitudes, and revolutions of the different bodies