HERO

OF ALEXANDRIA

ON PNEUMATICS

BOOK

An ornamental woodcut drop cap 'C' featuring a putto (cherub) standing in a landscape, holding a staff or measuring rod. In the background, there are hills and a small building.

Since the study of pneumatics spiritalis tractatio The Latin spiritalis refers to "spirit" or "breath," but in this technical context, it specifically concerns the properties of air, vacuum, and pressure—what we now call pneumatics. was considered by ancient philosophers as well as mechanicians original: "mechanicis" to be worthy of the greatest study—the former treating its power and potential through reason, and the latter through the actual effect of perceptible objects—I judged it necessary to bring into order those things handed down by the ancients, and to set forth those things which I myself have discovered. For in this way, those who hereafter wish to be occupied with mathematical studies will be greatly assisted by these matters. Furthermore, as I considered it appropriate for this treatise to be connected to the one concerning water-clocks aquaticis horoscopijs original: "horoscopijs," referring to clepsydrae or devices for measuring time via the flow of water, which was handed down in four books, I have determined to write about this subject as well.