The Pneumatics of Hero of Alexandria

...existing together with the vessel, let it be lowered into the water. Then, once the vessel is uncovered and its mouth is facing upward, water enters; the air indeed departs from the vessel, but being overcome by the great volume of water, it is mixed once more and compressed original: "complicatur"; literally "folded together," implying a reduction in volume until it becomes water. In the same manner, when the air within a cupping-glass original: "cucurbitula"; a bell-shaped vessel used in ancient medicine to create suction on the skin by heating the air inside is consumed and thinned by fire, and has escaped through the pores original: "raritatis"; refers to the microscopic gaps in the material of the vessel's walls through which the ancients believed thin substances could pass of the vessel, the emptied space within attracts the surrounding material, whatever it may be. But when the cupping-glass has "breathed" Hero uses the term "respirauerit" to describe the vessel cooling down and the internal pressure equalizing, air enters into the evacuated space, and the material is no longer attracted.

Therefore, those who say universally that there is no such thing as a vacuum original: "vacuum"; an empty space containing no matter can devise many arguments for these phenomena and perhaps prove more persuasive in their speech, yet they offer no demonstration perceptible to the senses. If, however, it can be shown through things that are visible and fall under the senses that a bulk vacuum original: "vacuum coaceruatum"; a large, continuous empty space, which Hero argues only happens by force is produced only contrary to nature, while by nature there exists a vacuum disseminated original: "disseminatum"; Hero is arguing for an "interstitial" vacuum, where tiny empty spaces exist between the atoms or particles of matter in small parts—and that bodies themselves, through compression, fill these disseminated voids—then those who offer merely "probable" reasons for these things should no longer be listened to.