Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/269

 tures themselves, which yet move naturally, and from an intern principle, do grow weary, and have need of rest to relax and refresh their members

Methinks I hear Kepler answer him to that, that there are some kinde of animals which refresh themselves after wearinesse, by rowling on the Earth; and that therefore there is no need to fear that the Terrestrial Globe should tire, nay it may be reasonably affirmed, that it enjoyeth a perpetual & most tranquil repose, keeping it self in an eternal rowling.

You are too tart and Satyrical, Sagredus: but let us lay aside jests, whilst we are treating of serious things.

Excuse me, Salviatus, this that I say is not so absolutely besides the business, as you perhaps make it; for a motion that serveth instead of rest, and removeth weariness from a body tired with travail, may much more easily serve to prevent the coming of that weariness, like as preventive remedies are more easie than curative. And I hold for certain, that if the motion of animals should proceed in the same manner as this that is ascribed to the Earth, they would never grow weary; Seeing that the weariness of the living creature, deriveth it self, in my opinion, from the imployment of but one part alone in the moving of its self, and all the rest of the body; as v. g. in walking, the thighs and the legs onely are imployed for carrying themselves and all the rest: on the contrary, you see the motion of the heart to be as it were indefatigable, because it moveth it self alone. Besides, I know not how true it may be, that the motion of the animal is natural, and not rather violent: nay, I believe that one may truly say, that the soul naturally moveth the members of an animal with a motion preternatural, for if the motion upwards is preternatural to grave bodies, the lifting up of the legs, and the thighs, which are grave bodies, in walking, cannot be done without violence, and therefore not without labour to the mover. The climbing upwards by a ladder carrieth the grave body contrary to its natural inclination upwards, from whence followeth weariness, by reason of the bodies natural aversness to that motion: but in moving a moveable with a motion, to which it hath no aversion, what lassitude, what diminution of vertue and strength need we fear in the mover? and how should the forces waste, where they are not at all imployed?

They are the contrary motions wherewith the Earth is pretended to move, against which the Authour produceth his argument.

It hath been said already, that they are no wise contraries, and that herein the Authour is extteamly deceived, so that the whole strength of the argument recoileth upon the Op-