Peripateticall institutions. In the way of that eminent person and excellent philosopher Sr. Kenelm Digby. The theoricall part. Also a theologicall appendix of the beginning of the world. / By Thomas White Gent.

LESSON IX.

Of the Motion of heavy and light bodies, and the Conditions of Acting.

1. FRom what has been said we collect, that, since the Sun either is Fire, or, at least, operates like fire, beating upon

Earth, Water, and all other bodies, with its Rayes; it summons out little bodies, which, sticking to its Rayes, are reflected with them and mov'd from the Centre to∣wards the Circumference.

2. By whose motion, all the rest must, of necessity, presse towards the Earth: and because the Motion of dense bodies is so much the stronger, the denser they are; and descending bodies, the more they de∣scend, the more they repell lesse descend∣ing ones; there must be, wheree're the Sun has any power, a Motion of dense bo∣dies towards the Centre and of rare to∣wards the Circumference; as experience teaches us there is.

3. Whence, first, we see, there can no where be any pure Elements: since, at least, the Rayes of the Sun and the bodies carry'd about with them are mingled eve∣ry where.

4. We see, too, that dense bodies are heavy, and contrarily, rare are light: and that there is not any inclination requisite in bodies, towards the Centre; as is evident by the experience of Pumps, by which, with an easie motion, a great weight of water is rais'd; or, as when we suck a Bullet out of the barrell of a long Gun.

5. We see, moreover, that, since this tumult, of little bodies ascending and descen∣ding, swarm's every where: place any body in it, it must needs be press'd upon by o∣thers every where about it; and the bo∣dies, which are aside on't, must perpetually pierce and enter into it, if they find in it lighter bodies which they can repell from the Centre: Whence, this tumult is even within all bodies, and, by vertue of it, all bodies are mingled.

6. Whence, again, it must needs be, that the thin parts of every body consist in a kind of perpetuall expiration; and con∣sequently, that every body, more or lesse, operates upon and affects other bodies which approach it round about, or acts in a Sphear; as we see by experience, in hot, cold, odoriferous, poys'nous bodies, and in Animals, &c. Every body, therefore, has a certain Sphear of activity, by this moti∣on; and its action depends upon this a∣ction.

7. Again, therefore, since its action is not effected but by an emission of its own parts; 'tis plain, it cannot act upon a di∣stant thing, but by a Medium; as also, that it suffers from that upon which it acts, if it be within that's Sphear of activity: the e∣manations

of the one running, by lines different, from the emanations of the o∣ther.

8. Again, 'tis evident, that, since these emanations are certain minutest particles; in a denser body more will stick to its parts, because its pores are narrow and hard to passe through: wherefore, with greater labour and time, and at the cost of more little particles, a dense body receiv's the nature and similitude of the body a∣cting upon it, retains more strongly, and works more vigorously then if it were rarer.

9. And, hence, the nature of intension and remission is evident; viz. because there are, within the same space, more or fewer of these particles: as also, why, in a denser body, a quality is more inten∣ded.