ON PNEUMATICS

BY HERO,

Translated by Master Giovanni Battista Aleotti

OF ARGENTA.

ON DRAWING WATER BY MEANS OF A

BENT TUBE, OR PIPE. Theorem One.

Let there be water in a vessel A. B., the surface of which is F. G. Within this vessel, let there be a bent pipe C.D.E. Hero refers to a siphon inserted with one leg, and let the leg C. H. be in the water, which will necessarily be filled with water up to H., level with the surface F. G., while the part H.D.I. remains full of air. I say that if we make a hole at I., and through it we draw out the aforementioned air with our mouth, the moisture—that is, the water—will follow it. This is because, as stated above, it is clear that a place cannot be entirely empty original: "vacuo"; a reference to the classical belief that nature abhors a vacuum. To this it must be added that if the hole I. through which we have drawn the air is level with the surface F.G., the pipe will not spill, but the water will remain at that limit in such a way that the part C.D.I. will remain full of it, even though, contrary to the order of nature, it remains suspended on high like a balanced scale, with the water being elevated from H. to D. and suspended downward from D. to I.

A woodcut diagram illustrating a siphon experiment. An ornate classical-style urn, labeled A and B, contains liquid with a surface level marked by a horizontal line F-G. A bent tube (siphon) marked C.D.E. is inserted into the urn. Point H is the bottom of the tube inside the liquid. Point D is the highest bend of the tube. Point I is an aperture on the outer vertical leg, level with the inner surface F-G. Point K is a lower aperture on the same leg, and E is the bottom of the tube. The urn is decorated with two dragon-shaped handles.

But if the hole at the end of the pipe is in a straight line as at K. meaning, at a lower point than the water's surface, the pipe will spill, and the water will flow out; because the part D.K., being heavier than the part D.H. D.K. is the longer, heavier column of water, will prevail and pull the latter, and it will flow out of this channel until the surface of the water (which, as the channel flows, will continuously drop in the vessel) has reached the level of the hole K.; and at that point it will no longer flow—