The Pneumatics

For the medical vessels which are made of glass and have a narrow mouth: when they wish to fill them with liquid, they suck out the air contained within them by mouth, and closing the orifice with a finger, they invert them into the liquid; and when the finger is released, water is drawn into the emptied space, and that same liquid is carried upward contrary to nature. And that which happens concerning the cupping-glass is not at all foreign to what we have said. For when applied to the body, not only do they not fall, though they possess manifest weight, but they draw the adjacent matter through the pores of the body for the same reason. For the fire introduced into them consumes and rarefies the air contained within them, just as other bodies are consumed by fire and changed into thinner substances. I mean air, water, and earth. For that they are indeed consumed is manifest from the coals left behind. For these, while maintaining the same bulk which they had from the beginning before combustion, or one slightly smaller, differ very much in weight. But those parts in bodies which are consumed pass through smoke into fiery, airy, and earthy substance. For those things which are thinner in