Concerning Motive Forces.

Inasmuch as the aforementioned pipe D. must contain as much water in length—or a little more—as the aforementioned siphon contains air from the surface of the water up to the mark E. (which is the water level), thus this example demonstrates that if one draws out the air that is inside the siphon (either by the mouth by suction, or by the pipe D.), the water will follow to avoid a vacuum original: "pour ne souffrir vacuité", and will have its course, provided that it descends lower than its level.

Theorems of Hero's Spiritalia original: "Herone spiritali Theoremes." This refers to Hero of Alexandria, a 1st-century mathematician whose work Pneumatica—often called Spiritalia—was a primary source for Renaissance engineers.

This present THEOREM has been poorly understood by those who have translated Hero; they show how to draw water through a large siphon by fitting a vessel to the end of said siphon instead of the pipe D. Such a vessel can have no effect, because it will not draw water into leg B. of the siphon any higher than the height of the vessel itself. Even if it contains as much water or more than the said siphon, the said water will still not rise any higher than the thickness or height of the said vessel.

THEOREM IIII.

Water cannot rise by its own means; unless it is to descend lower than its level.

A woodcut illustration depicts a wooden table. On the table's surface is a wide, shallow basin labeled 'A' filled with water. A strip of porous cloth or fabric is draped from inside the basin over the rim. Water is shown dripping from the end of the cloth into a tall pitcher or jug resting on a lower shelf of the table structure.

The second means of making water rise is by its own means Here, De Caus refers to the internal properties of the materials and gravity., and it shall be done in this manner: let there be a vessel full of water marked A., in which there shall be a piece of cloth half a foot long and one inch wide. This must be wetted through and through and placed in the vessel so that one of the ends is inside it and the other end outside. Then the water that is at the outer end will, by its weight weight: "pesanteur," referring here to the gravitational pull on the liquid within the saturated cloth, draw that which is in the vessel and make it rise along the piece of cloth (as occurs in a siphon) until the water at the inner end is level with the outer end, and then it will cease to flow.

THEOREM V.

Water will rise by means of fire, higher than its level.

A scientific diagram shows a spherical metal vessel labeled 'A' (described as a "copper ball") supported by a three-legged stand. A hand-held torch is applied to the bottom of the sphere. On the side is a small capped opening labeled 'D' (a "vent-hole"). A vertical pipe labeled 'B' and 'C' extends from the top of the sphere; the bottom of the pipe 'C' is inside the sphere near its base. Due to the heat, a jet of water is forced out from the top of the pipe.

The third means of making [water] rise is by the aid of fire, from which various machines can be made; I will give here a demonstration of one. Let there be a copper ball copper ball: "balle de cuiure," a spherical pressure vessel marked A., well-soldered all around, to which there will be a vent-hole vent-hole: "souspiral," a small opening used for filling or pressure regulation marked D. through which one will put the water, and also a pipe marked B. C. which will be soldered to the top of the ball, and the end C. shall approach near the bottom without touching it. Afterward, the said ball must be filled with water through the vent-hole, then stopped up well and placed on the fire. Then the heat striking against the said ball will make all the water rise through the pipe B. C.