The pneumatics of Hero of Alexandria

Chapter 50: 46. The World represented in the Centre of the Universe.

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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.

46. The World represented in the Centre of the Universe.

The construction of a transparent globe containing air and liquid, and also of a smaller globe, in the centre, in imitation of the world. Two hemispheres of glass are made (fig. 46): one of them is covered with a plate of bronze, in the middle of which is a round hole, To fit this hole a light ball, of small size, is constructed, and thrown into the water contained in the other hemisphere: the covered hemisphere is next applied to this, and, a certain quantity of liquid having been removed from the water, the intermediate space will contain the ball; thus by the application of the second hemisphere what was proposed is accomplished.