The Pneumatics of Hero of Alexandria

...we have organized the matter as has been stated. For through the combination of air, fire, water, and earth—whether three elements or all four coming together—various arrangements are produced. Some of these provide for the necessary needs of our life, while others evoke a certain awesome wonder original: "terribilem quandam admirationem." In Hero's context, "terrible" implies a sense of awe or being struck by the seemingly miraculous nature of mechanical automata..

Concerning the vacuum.

But before we proceed to the matters at hand, we must discuss the vacuum. For some claim that there is absolutely no vacuum anywhere in the universe; others argue that while no large, continuous vacuum exists naturally coacervatum vacuum A "collected" or "massed" vacuum—an empty space of significant size, as opposed to microscopic gaps., it is instead distributed in tiny parts through air, moisture, fire, and other bodies. It is most appropriate to agree with this latter view. From the things that are visible and perceived by the senses, it will be demonstrated in the following pages that this is the case. For vessels that appear empty to many are not actually empty, as is commonly thought, but are full of air. Air, according to the opinions of natural philosophers original: "ijs, qui de natura tractant," literally "those who treat of nature.", consists of small, light particles original: "corporibus." Hero is introducing a corpuscular or "atomistic" view of matter here. that are generally invisible to us.