Sagr.Hold a little, I pray you. Tell me Simplicius, when two Knights encounter each other, tilting in open field, or when two whole Squadrons, or two Fleets at Sea, make up to grapple, and are broken and sunk, do you call these encounters contrary to one another?
Simpl.Yes, we say they are contrary.
Sagr.How then, is there no contrariety in circular motions. These motions, being made upon the superficies of the Earth or Water, which are, as you know, spherical, come to be circular. Can you tell, Simplicius, which those circular motions be, that are not contrary to each other? They are (if I mistake not) those of two circles, which touching one another without, one thereof being turn'd round, naturally maketh the other move the contrary ** As you see in a Mill, wherein the implicated cogs set the wheels on moving. way; but if one of them shall be within the other, it is impossible that their motion being made towards different points, they should not justle one another.
Salv.But be they contrary, or not contrary, these are but alterations of words; and I know, that upon the matter, it would be far more proper and agreeable with Nature, if we could salve all with one motion onely, than to introduce two that are (if you will not call them contrary) opposite; yet do I not censure this introduction (of contrary motions) as impossible; nor pretend I from the denial thereof, to inferre a necessary Demonstration, but onely a greater probability,A third confirmation of the same Doctrine. of the other. A third reason which maketh the Ptolomaique Hypothesis lesse probable is, that it most unreasonably confoundeth the order, which we assuredly see to be amongst those Cœlestial Bodies, the circumgyration of which is not questionable,The greater Orbs make their conversions in greater times. but most certain. And that Order is, that according as an Orb is greater, it finisheth its revolution in a longer time, and the lesser, in shorter. And thus Saturn describing a greater Circle than all the other Planets, compleateth the same in thirty yeares: Jupiter finisheth his; that is lesse, in twelve years: Mars in two: The Moon runneth thorow hers, so much lesse than the rest, in a Moneth onely. Nor do we lesse sensibly see that of the Medicean Stars,The times of the Medicean Planets conversions. which is nearest to Jupiter, to make its revolution in a very short time, that is, in four and forty hours, or thereabouts, the next to that in three dayes and an half, the third in seven dayes, and the most remote in sixteen. And this rate holdeth well enough, nor will it at all alter, whilest we assign the motion of 24 hours to the Terrestrial Globe, for it to move round its own center in that time; but if you would have the Earth immoveable, it is necessary, that when you have past from the short period of the Moon, to the others successively bigger, until you come to that of Mars in two years, and from thence to that of the bigger Sphere of Jupiter in twelve years, andfrom
