Book One

A horizontal decorative woodcut band featuring intricate scrolling floral and foliate patterns.

SECOND DEFINITION.

An engraving of a scientific apparatus consisting of a large rectangular tank labeled 'A' and a tall, thin vertical pipe labeled 'B' at the top (with a funnel-shaped basin) and 'C' where it enters the tank. The tank appears to contain liquid. This illustration demonstrates the resistance of trapped air to being displaced by water.

The place of air, the second element, is imagined between the element of fire and the earth. Vitello Witelo (Latinized as Vitellio) was a 13th-century friar and scientist whose work on optics was a standard reference for Renaissance physicists. proves by his optical lines that the clouds are distant from the earth by 52,000 paces, which is about 26 French leagues; and thus this distance is divided into two regions. One is called the "middle" region because it is between the third or supreme region of fire (of which we have spoken) and the lower region, which is the one we touch. As for the middle region, it is cold and filled with clouds and mists. Experience gives us knowledge of this in the high mountains of the Alps and the Pyrenees, where snow remains in the heart of summer.

The lower region, as I have said, is the one we touch, where the air is much warmer than in the mountains; the reason is due to the reflection of the Sun's rays, which, hitting the flat surface of the earth and being unable to pass further, stop and heat the lowest air. But in the mountains, the Sun's rays do not provide such a reflection, but rather slide along them, especially on the slopes that do not face the South. I say then that air is a cold element which has no other heat than that which is given to it by the Sun. It also has no humidity in its nature, as some have wished to say; this will be demonstrated in the definition of water. It is also called "light," for whatever quantity of air there is in a vessel, the vessel will be no heavier for it.

As for what is said here—that it can be compressed—I will give an example here. Let there be a vessel of lead or copper, well-closed and soldered all around, marked A, in which there will be a pipe marked B. C., of which the end C comes near the bottom of said vessel by about an inch, and at the end B there will be a small recipient to receive the water. You will pour water into said recipient, and from there it will descend into the vessel. Inasmuch as the air that is inside said vessel cannot get out, and because there must be room for the water, one will not be able to fill the vessel. If the pipe B. C. is ten or twelve feet high, the water will enter only about a third of the way, so much so that the air, pressing against itself, will cause a compression and will even make the vessel bulge if it is not very thick; this demonstrates that air compresses itself, and that this compression creates violence.

As can be seen in various machines in this book, the violence will be great when water is exhaled into air In the 17th century, "exhaling into air" was a way to describe the transformation of water into steam through heat. by means of fire and that said air is enclosed. For example, let there be a copper ball a foot or two in diameter and an inch thick, which will be filled with water through a small hole; this hole will afterward be plugged very tightly with a nail, so that neither water nor air can get out. It is certain that if one puts said ball on a large fire so that it becomes very hot, a compression so violent will be created that the ball will burst into pieces with a noise similar to a petard original: "petart". A petard was a small explosive device used in warfare to breach gates or walls..