BOOK ON PNEUMATICS

is cast between the particles of sand, it is similar to the voids contained within the air. For this reason, when some force is applied, it happens that the air is condensed and settles into the spaces of the voids, as the physical bodies are compressed together against their natural state. However, when the pressure is released, the air is restored again to its previous order due to the natural tension of bodies—just as occurs with shavings of horn original: "cornuum ramentis." Shavings or scraps of animal horn were frequently used in ancient science to demonstrate elasticity because they spring back to their original shape. and with dry sponges which, if released after being compressed, return again to the same state and occupy the same volume molem.

In the same way, if by some force the particles of air are pulled apart from one another and a larger empty space is created against nature, they rush back toward each other again. For through a vacuum, a swift motion of bodies occurs, as there is nothing obstructing or pushing them back until the bodies are once again joined together.

If someone, therefore, takes a very light vessel with a narrow mouth and, applying it to their mouth, sucks out the air and then lets go, the vessel will immediately hang from the lips; the vacuum vacuo Hero is describing the effect of a partial vacuum creating suction, a foundational concept in pneumatic engineering. draws the flesh inward so that the emptied space may be replenished. From this, it is clear that the space within the vessel has become an internal vacuum. But this is also made manifest by another reasoning. For where