The Pneumatics

more brightly illuminated, those same rays likewise penetrating through one another. But penetration also occurs through bronze, through iron, and through all other bodies, just as that which happens in the case of the marine torpedo. But indeed, it has been demonstrated that a collective vacuum is produced contrary to nature, both by a light vessel applied to the mouth and by the physician’s egg. Therefore, since there are many demonstrations concerning the nature of the vacuum, we have judged those which we have just brought forward to be sufficient; for the demonstrations were made through the senses themselves. Universally, therefore, it may be said that every body consists of minute bodies, between which are scattered vacuities smaller than the particles. Wherefore we say in an improper sense that nothing is a vacuum unless some force intervenes, but that all things are full either of air, or of moisture, or of some other substance. Moreover, as much as any one of these departs, just so much of another follows and refills the evacuated place. Furthermore, that a collective vacuum does not exist by nature without the intervention of some force; and again, that there is never a complete vacuum, except when produced contrary to nature. These things having been explained, next the theorems which