Corpus Hermeticum with Pneumatica and Ocellus Lucanus

This aforementioned body differs from the surrounding liquid itself, but the fact that there are voids kena original: "κενὰ" (kena). Hero uses this term to describe the microscopic "empty spaces" or "pores" between the particles of a substance. can be understood from the following.

Nothing of such a nature—whether through water, or through air, or through any other body—could allow light to pass through it, nor could heat thermotēs original: "θερμότης" (thermotēs). or any other bodily power. For instance, consider how the sun's rays hēliou aktinas original: "ἡλίου ἀκτῖνας" (hēliou aktinas). pass through water to the bottom of a vessel angeiou original: "ἀγγείου" (angeiou). A general term for a container, jar, or flask..

If it were the case that the water had no pores, but the light forced its way through the liquid by violence, it would follow that vessels already full would overflow. However, this is clearly not seen to happen. But this is also evident for another reason: if the light passed through the water by force, it would be deflected original: "διαθλαθῆναι" (diathlathēnai). While this later became the technical term for "refraction," Hero uses it here in the sense of being broken or diverted by impact. many times; it would not fail to be reflected original: "ἀνακλώμεναι" (anaklōmenai). In ancient optics, this term covered both reflection and refraction. toward the upper region, yet we see the rays reaching the bottom.

In reality, those rays which strike the actual particles of the water are, as it were, struck back and reflected toward the upper region. However, those rays which fall into the voids of the water, striking only a few particles, are the ones that reach the floor of the vessel. It is also clear that voids exist in the water from the fact that when wine is poured into water, it is seen to spread through all the [spaces].