The Ingenious and Curious Pneumatic Motions of Hero

it will stop for the same aforementioned reason. But if we make the hole at E., the water will flow out until the water in the vessel has lowered so that its surface is level with the mouth of the pipe C. And if we want to draw out all the water from the vessel, we will lower the mouth C. down to the bottom of the vessel, though remaining as far from it as we deem sufficient for the flow of the water. The reason why the pierced and bent pipe produces this effect is, according to some, because the quantity of water that is in the greater leg has the force to attract, and in effect pulls the lesser one. But how false this cause is, and in what error everyone who believes this finds himself, can be seen from this: Let a pipe be made such that the inner leg is long and thin, and the outer one much shorter but wider, so that it contains a greater quantity of water than the long leg, and let it be filled with water. Then, having placed the larger one in a vessel of water or in some well, it will be the same as if we were to make the outer leg flow. Since it has within itself a greater abundance of water than the inner one, this will also have the force to attract the water of the greater one, and with it will also pull what is in the well; and when it begins to flow, it will draw it all out, or it will always flow, because the abundance of the outer water is greater than that which is in the inner leg. But because it does not appear whence this derives as truth, we therefore do not approve of the aforementioned cause. Let us see the natural cause of this, saying that every continuous and still moisture takes a spherical surface whose center is the same as that of the earth; but if it is not standing still, it flows until it reduces itself to a spherical surface, as has been said above. Let us take two vessels, and in each of them let water be placed; let us also fill the pipe with water, and with our fingers let us stop the mouths of it, placing one end in one of the aforementioned vessels so that it is submerged in the water, and likewise let us place the other leg in the other, and all the water will be made continuous; because the water that is in both vessels comes to be joined with that which is in the pipe so that it is all continuous. If, therefore, the said waters, which were first in the vessels, are on one and the same surface, made continuous by the bent pipe submerged in them, they will be quiet and stand still; but if one of them is lower than the other, because the water is made continuous, it is also necessary by this continuity that the higher one flows into the lower one until either all the water that is in the aforementioned vessels is reduced to one and the same surface, or until one of the said vessels is empty. But if they equalize on one and the same surface, the waters that are in these vessels will stop, both one and the other; so that the water that is in the pipe will also remain stationary, in such a way that given that one leg and the other are equally submerged in each of said surfaces (granted that they are equal), the water that is in it will remain still. The pipe thus being suspended so that it does not incline either here or there, it is again necessary that the water stops, whether it has equal width or one leg is much larger than the other, which is not the cause of why the water stands still or flows; but it derives from the mouths of it standing equal in the water. Now let us say why (the pipe being suspended) the water does not flow due to its gravity, being lighter, having air underneath? It is for no other reason, certainly, than that the place of the whole cannot be a vacuum.