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The pneumatics of Hero of Alexandria

Chapter 57: 53. A Vessel in which Water and Air ascend and descend alternately.
By of Alexandria Hero
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About This Book

A systematic practical handbook of machines and demonstrations that uses air, steam, heat, and water to produce mechanical effects. The text gives clear descriptions, construction details, and diagrams for siphons, valves, pumps, fountains, jets, self‑acting mechanisms, and ritual or theatrical contrivances driven by pressure and temperature changes. Explanations focus on the mechanical principles behind pneumatic and hydraulic behaviors and on ways to control flow and timing, with numbered propositions that pair instructional steps with illustrative figures for building and operating each apparatus.

53. A Vessel in which Water and Air ascend and descend alternately.

There is also another contrivance by which liquid is borne steadily upwards and remains, so as to seem perpetually ascending. Let A B (fig. 53), be a perfectly air-tight pedestal, furnished with a partition, C D, and a cylindrical glass cover, E F, also perfectly air-tight. In the cover E F let there be a tube, G H, reaching nearly to the top, and passing through an orifice in the partition C D, and another tube, K L, passing through the top of the pedestal but not descending quite so low as the partition. In the pedestal, and outside the glass cover, let there be an aperture, M, through which the vessel A D is to be filled, and near the bottom of the pedestal a spout, N; also one other tube, X O, passing through the partition and reaching nearly to the bottom of the pedestal, through which the vessel C B may be filled. If the spout, N, be closed the air in C B will pass out through the tubes G H, K L, and the hole M; and when C B is full we must fill A D through the hole M, for the air contained in it will pass out through the same hole. Now, if we set the spout N free, the air in the glass cover will pass through the tube G H into the void space left in C B, and water will ascend from A D through the tube K L into the void space left in the cover, while into the void of the vessel A D air will enter through the aperture M; and this will go on until the glass cover is filled: but the spaces A D, C B, E F, must be of equal capacity that the air and water may take the place of one another. When C B is exhausted and the continuity of the air is broken, the water will again descend out of the glass cover into A D, air passing into the cover through the spout N and the tube G H. The air in A D will pass out through the aperture M.