Lectures de Potentia Restitutiva, or of Spring

According to the difference of these vibratory motions of the surrounding masses, all bodies are more or less powerful in preserving their specific shapes.

All bodies near the Earth are surrounded by a fluid, subtle matter. By the differing velocity of its parts, all solid bodies are kept together in the specific shapes they were left in when they were last in a fluid state. Furthermore, all fluid bodies whatsoever are mixed with this fluid, which is not forced out of them until they become solid.

Fluid masses differ from solids only in this: all fluids consist of two types of particles. The first is this common solvent original: "Menstruum"; a term from alchemy and early chemistry referring to a substance that dissolves or holds others in suspension near the Earth, which is scattered between the vibrating particles belonging to that mass, and so participates in its motions and vibrations. The other type, solids, differs by either excluding that motion entirely or not participating in it.

Though the particles of solid bodies do, by their vibratory motions, prevent this fluid from coming between them where their motions directly touch, there are nonetheless certain spaces between them. These spaces are not protected by the motion of the particles from being permeated by the heterogeneous original: "Heterogeneous"; meaning consisting of different or diverse ingredients fluid solvent.

These spaces—which are unprotected by the physical mass and vibratory motion of the particles, and are consequently permeated by the subtle, surrounding, diverse fluid—are what we call the invisible pores of bodies.

The motions of these bodies are in reciprocal proportion to their size. That is, the larger or more powerful the body is, the slower is the motion with which it composes its particles; and the smaller the body is, the swifter is its motion.

The smaller the particles of bodies are, the more closely they approach the nature of the general fluid.