INTRODUCTION

A machine is ingenious cleverly constructed because in the refinement of machines, the wit of the artificer plays a greater role than the material: of things, such as woods, iron, ropes, sinews, water, air, spirit, and the like: [they are] proportioned, having regard to the form, the site, the time, and the distance. [It is] apt to operate with violence because all machines are built either to give motion to things that do not have it, or to increase their natural motion, or to move them contrary to how they would move naturally. The art of making them is founded, as has been said, partly on reasons and partly on experience. Experience is a knowledge acquired by means of many similar trials learned by the senses. The inexperienced artificer often does not achieve the end because of the material he is treating, the nature of which is perhaps poorly known to him, but he who operates by means of experience, even if he does not know the reason for the effects, has practice as his guide, and it does not let him wander entirely, although experience is still much less noble than art.

An instrument is different from a machine because it is simpler, as are the hammer, the saw, and the like. There is also another difference: the instrument does not move to operate by itself, but some machines do. A work is that labor which remains after the operation of art. Operation is that progress which art makes while it works. An end is that toward which the operations are directed by the operator. Order is that which contains the before and the after in the location of the parts: its opposite is confusion. Proportion is the comparison of parts of the same kind that tend toward the same end. Position? is of two sorts: one that comes from chance or from necessity, the other from the art that teaches what thing is fitting to place in what place, or, as Vitruvius said, it is fitting with the location? of things.

Regarding spirit, what it is and how it is considered differently by various [thinkers], it is defined thus: Physicians said it was that faculty divided into three parts—namely, animal, vital, and natural—whence the soul performs its operations. Aristotle maintained that it was aura or wind caused by hot and dry exhalations which, ascending to the second region of the air, and there, because it moves in a circle, taking their lateral movement, they become winds. But the Latins were of a different opinion, namely, that because air is of its nature cold,