The Pneumatics of Hero of Alexandria

B 2

if we should force an injection [of air] with great strength, the vessel will be broken before it receives anything else, since it is [already] full; for the bodies of air original: "aeris corpora"; Hero conceives of air as being composed of discrete physical particles rather than a continuous, immaterial substance. cannot be contracted into a smaller size [if they are already touching]. Therefore, it would be necessary for them to have certain intervals original: "interualla"; referring to the tiny spaces or voids between the particles of air. within themselves, into which, when compressed, they might occupy a smaller mass.

However, this is not considered probable [by those who deny the vacuum], as they believe no vacuum exists at all; and since bodies are joined to each other along every surface, and likewise to the circumference of the vessel, they cannot, when pushed, create space anywhere if no vacuum exists. For this reason, in no way can anything from the outside be sent into the sphere unless some part of the air previously contained within it escapes, provided that the entire space is packed and continuous, as they Referring to the "Plenists," such as the followers of Aristotle, who argued that "nature abhors a vacuum" and that all space is completely filled with matter. believe.

But if someone, bringing a siphon original: "siphonem"; the narrow tube or pipe mentioned on the previous page. to their mouth, wishes to blow into the sphere, they will inject much spirit original: "spiritum"; here, the air or breath acting as a pressurized force., even though the air already inside does not escape. Since this always happens in this way, it is clearly demonstrated that a contraction of the bodies existing within the sphere occurs within the interspersed vacuums original: "vacua implicata"; a central concept in Hero's physics, suggesting that while large vacuums do not occur naturally, tiny voids are distributed between the particles of all matter, allowing for compression and expansion.. This contraction, however, occurs contrary to nature due to the force of the injection—

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