course, varies in length as we move the pea, will form what in geometry is called a radius vector. Now, if the orange be understood as the Sun, and the pea as a planet revolving about it, then the revolution should be made at such a rate—with a velocity so varying—that the radius vector may pass over equal areas of space in equal times. The progress of the pea should be—in other words, the progress of the planet is, of course,—slow in proportion to its distance from the Sun—swift in proportion to its proximity. Those planets, moreover, move the more slowly which are the farther from the Sun; the squares of their periods of revolution having the same proportion to each other, as have to each other the cubes of their mean distances from the Sun.
The wonderfully complex laws of revolution here described, however, are not to be understood as obtaining in our system alone. They everywhere prevail where Attraction prevails. They control the Universe. Every shining speck in the firmament is, no doubt, a luminous sun, resembling our own, at least in its general features, and having in attendance upon it a greater or less number of planets, greater or less, whose still lingering luminosity is not sufficient to render them visible to us at so vast a distance, but which, nevertheless, revolve, moon-attended, about their starry centres, in obedience to the principles just detailed—in obedience to the three omniprevalent laws of revolution—the three immortal laws guessed by the imaginative Kepler, and but subsequently demonstrated and accounted for by the patient and mathematical Newton. Among a tribe of philosophers who pride themselves excessively upon 6*
