The Reasons of Motive Forces

it will be necessary to draw out the water from within, and you will find exactly the same quantity that was put in; so it can be seen that the water which evaporated (the first time the vessel was placed on the fire) returned to water the second time when the said vapor was enclosed in the vessel and it cooled on its own. Another demonstration of this can also be made: after putting a measure of water into the vessel, one must tightly plug the vent-hole vent-hole: "souspiral," a small opening or "breather" used to regulate pressure or allow air to escape and open the tap D. Then place the said vessel on the fire and put a pot under the tap. Then the water in the vessel will rise by the heat of the fire and come out through tap D. But about a sixth or eighth part of all the water will fail to come out, because the force of the vapor that causes the water to rise comes from the water itself; this vapor will come out with great force after the water has exited through the tap. There is also another example with quicksilver, otherwise called mercury quicksilver: mercury, the only metal that is liquid at room temperature, which is a flowing mineral. When heated by fire, it evaporates entirely into vapor and mixes with the air for a time, but after the said vapor has cooled, it returns to its original nature as quicksilver. Experience shows this, as if one places some gilded vessel in a room where quicksilver has been evaporated, the vapor will attach itself entirely to the vessel, and it will be found afterwards to be pure quicksilver. But water vapor is much lighter; thus it rises, as we have said, up to the middle region The "middle region" refers to the middle layer of the atmosphere in Aristotelian meteorology, where clouds were thought to form..

THEOREM II.

Everything known to man is filled with the four elements; this is why there can be no vacuum known to us. To think (as some have wished to say) that there is a void above the elements is an opinion without proof or demonstration. Likewise, to say that all this great space is filled with air is unlikely, for divine providence has made nothing in vain original: "inutile". If the space between the firmament and the element of air were filled with air, it would be useless, for no creature has any need for air above the middle region. To avoid error in this opinion, it is better to say that this great space is filled with a fifth essence fifth essence: also known as the "aether," a celestial substance believed to be distinct from the four earthly elements unknown to us. Epicurus was one of the most excellent Philosophers of his time; however, his opinion regarding Atoms and the vacuum is quite contrary to an example I shall give here. He says that there is nothing which is not a body, and that Atoms are individual meaning "indivisible," from the Greek atomos and solid bodies. He says there are two kinds: some composite (which we call solid bodies) and others simple, from which the composition of things is made. This composition occurs through the hooking together of solid Atoms (for he admits no others), which turn, veer, and collide within the empty cavity of the world. The example I shall demonstrate will be a vessel of lead or copper marked A, closed and plugged on all sides, which shall be filled with water through the vent-hole B. Then, let the said vent-hole be tightly closed. If one makes a small hole at the bottom of the vessel at point C, no water will come out, because a vacuum vacuum: "vacuité" in the original, referring to a space entirely devoid of matter cannot be made in the vessel. But if one allows air to enter the vessel by opening the vent-hole B, then the water will flow out, and the air will take its place. Now, if Epicurus's opinion were true, and nature allowed a vacuum (as he says there is between each Atom), the water would flow out even if the vent-hole were closed, since it is a heavy and flowing element. Thus, we say that nature permits nothing known to us to be a vacuum.

A woodcut illustration depicts a physical experiment. It shows a rectangular box or vessel labeled 'A' resting on a wooden stand. On top of the vessel is a funnel or opening labeled 'B' with what looks like vapor or steam rising from it. At the bottom right corner of the vessel is a small spout or hole labeled 'C' with liquid dripping into a small basin or onto the stand.