ADDITION BY ALEOTTI regarding the impossibility of any void, and the inability of the Element of Air to remain compressed.

IN Conformity with what Hero has said above, one may add that if we take an arquebus rod a ramrod used for loading a firearm, at the end of which is its well-fitted cleaner, and we drive it into an arquebus barrel, drilled most precisely in a straight line with great excellence, then—having closed the touchhole—if we pull it almost out (which we will be able to do, though with some difficulty as the void that would remain in the lower part resists us, because the air cannot succeed into it; if I say, once pulled almost out, we let it go, that void—because it cannot be, unless violated by nature—will pull the rod back with violence to fill itself immediately). Just as also for proof, that the Element of Air cannot stay except in the quality of its nature, and as God Almighty created it, if—the touchhole of the said barrel being closed—we drive the aforementioned rod inside (which we will feel, because Air is a body), we will do it with effort, and that Air will come to be compressed. And if, having pushed it down as far as we can, we release it freely, the violated air, not being able to remain constipated compressed/tightly packed, will erupt and drive the rod out with fury to return immediately (once the violence has ceased) to its nature. Whence it becomes clear to us that by driving a ball into it, with the touchhole closed, the compressed air drives it out with violence to return to its nature. And if the former demonstrates to us that a void cannot exist, this one makes clear to us that this Element cannot exist except in the limit of its nature, as its Creator created it.

It is further proved that no void can exist by those glass vessels which women are accustomed to use to reduce and partially evacuate milk from their breasts, which, after they have given birth, within the space of two or three days, usually arrive in such abundance that, if they do not evacuate them for the newborn babies, they would cause in themselves (if the breasts were not reduced) hardness and very grave maladies. These have, as is known, a body in which there is a hole so large that, by resting the vessel on the breast, the nipple enters comfortably inside; and in another part they have a neck so long that they take it into their mouth, then, having sucked out the air that is in the vessel, the milk which comes out of the breast immediately succeeds into its place. And for those vials which they also use for the said effect: these take a glass vial with a neck so wide in the upper part that it can accommodate the nipple of the breast, and they heat the body well with its fire, until the heat, penetrating through the voids, drives out the air through the thinness of the glass, filling the body of the vial with very thin vapor. And when the said body is well heated, they immediately place the mouth of the vial's neck to the breast, inserting the nipple inside, and because that thin igneous vapor cannot remain shut up therein, it exits through those voids of the glass through which it entered, and to rise on high to its place it makes its way. Even if it is transmuted into aerial substance by the surrounding air, and because air cannot enter through these meatuses passages which are very thin, not being able to be void, that body which cannot remain empty immediately pulls the milk from said breast and, devouring it, comes to fill itself; and once completely filled, it no longer pulls, as also if it is opened in some part, it lets the air enter it.

Similarly, the fires that are lit at the mouths of the furnaces (in which stones, lime, and earthenware vessels are cooked) are pulled inside by those furnaces by the void; for the vapor of the fire, having driven out the air that is inside, vanishes and evaporates on high. And the fire being at the mouth of the furnace prevents air from entering, but because there cannot be a void as the vapor vanishes, it is necessary that the fire fills the empty body that would remain in the furnace, because as the vapor exits, the path to the air is closed, and not being able to be void, it is necessary that the fire succeeds in its place. From these things it is clear with what excellence Hero has proved that a void is not conceded at all, unless violated and outside of Nature.

OF THE PNEUMATICS OF HERO,

Translated by Mr. Giovanni Battista Aleotti OF ARGENTA.

ON DRAWING WATER BY WAY of a bent Tube, or Pipe. First Theorem.

A technical illustration of a siphon mechanism. A large vessel shaped like an amphora, labeled 'A' at its shoulder and 'B' at its base, contains a liquid up to a level line marked 'F' on the left and 'G' on the right. A bent tube, or siphon, is inserted through the top. The inner leg of the tube descends into the liquid, while the outer leg hangs down outside. The highest point of the tube is labeled 'D'. Points along the tube are labeled 'C', 'H', 'I', 'E', 'K', and '6'. 'H' is the water level inside the tube, and 'I' is a point on the outer tube level with the water surface 'F.G.'.

LET there be water in a vessel A.B., the surface of which is F.G., and in this let the bent pipe C.D.E. be inserted with one leg, and let the leg C.H. be in the water, which will naturally fill up to H., level with the surface F.G., and the part H.D.I. will be full of air. I say that if we make a hole at I., and through it pull the said air with the mouth, the moisture, that is, the water, will follow; for, as has been said above, it is clear that a place of complete void cannot exist. And to this it must be added that if the hole I., through which we have pulled the air, is in line with the surface F.G., the pipe will not spill, but the water will remain up to that limit, such that the part C.D.I. will remain full of it, even though against the order of nature it remains suspended on high like a balanced scale, the water standing elevated from H. to D., and suspended downwards from D. to I. But if the hole at the end of the pipe is in a straight line, as at K., the pipe will spill, and the water will run out; because the part D.K., being heavier than the part D.H., will overcome and pull it, and it will flow out of that channel until the surface of the water—which, as the channel continues to flow, will drop in the vessel—has reached the level of the hole K., and there, no longer flowing, it will stop for the same aforementioned reason;