Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/34

 and others more slowly than the simple; as for example, Lead, and Wood, in comparison of earth; and therefore amongst these motions, which call you the simple, and which the mixt?

I would call that simple motion, which is made by a simple body, and mixt, that of a compound body.

Very well, and yet Simplicius a little before you said, that the simple, and compound motions, discovered which were mixt, and which were simple bodies; now you will have me by simple and mixt bodies, come to know which is the simple, and which is the compound motion: an excellent way to keep us ignorant, both of motions and bodies. Moreover, you have also a little above declared, how that a greater velocity did not suffice, but you seek a third condition for the definement of simple motion, for which Aristotle contented himself with one alone, namely, of the simplicity of the Space, or Medium: But now according to you, the simple motion, shall be that which is made upon a simple line, with a certain determinate velocity, by a body simply moveable. Now be it as you please, and let us return to Aristotle, who defineth the mixt motion to be that compounded of the right, and circular, but produceth not any body, which naturally moveth with such a motion.

I come again to Aristotle, who having very well, and Methodically begun his discourse, but having a greater aim to rest at, and hit a marke, predesigned in his minde, then that to which his method lead him, digressing from the purpose, he comes to assert, as a thing known and manifest, that as to the motions directly upwards or downwards, they naturally agree to Fire, and Earth; and that therefore it is necessary, that besides these bodies, which are neer unto us, there must be in nature another, to which the circular motion may agree: which shall be so much the more excellent by how much the circular motion is more perfect, then the streight, but how much more pefect that is than this, he determines from the greatness of the circular lines perfection above the right line; calling that perfect, and this imperfect; imperfect, because if infinite it wanteth a termination, and end: and if it be finite, there is yet something beyond which it may be prolonged. This is the basis, ground work, and master-stone of all the Fabrick of the Aristotelian World, upon which they superstruct all their other properties, of neither heavy nor light, of ingenerable incorruptible, exemption from all motions, some onely the local, &c. And all these passions he affirmeth to be proper to a simple body that is moved circularly; and the contrary qualities of gravity, levity, corruptibility, &c. he assigns to bodies naturally moveable in a streight line, for that if we have already discovered defects in the foundation, we may rationally question what soever may far-