The Pneumatics

For let a sphere be constructed having the thickness of a metal plate, so that it may not easily be broken, containing about eight cotylae, and closed on all sides. It is necessary, therefore, to perforate it and to insert a bronze siphon—that is, a slender tube—not touching the place which is diametrically opposite to the perforated point, so that water may be able to flow; but let another part of the tube project about three fingers' breadth outside the sphere. It is necessary to seal the circumference of the hole through which the siphon is inserted with tin, encompassing both the siphon and the outer surface of the sphere, so that when we wish to blow through the siphon with the mouth, the spirit may in no way escape from the sphere. Let us then examine what happens. For air being present within it, as in other vessels which are called empty, and filling the whole space inside it, and being applied by a certain continuity to its circumference—no place, in short, being entirely empty, as they suppose—we could neither introduce water nor other air, unless the air previously within it were to withdraw; and