The Pneumatics

If we were to force an injection with great power, the vessel would burst before it received anything since it is full; for the bodies of air cannot be contracted into a smaller magnitude. Wherefore it would be necessary for them to have certain intervals within themselves, into which, when compressed, they might occupy a smaller volume. This, however, is not probable if no vacuum at all exists; and since bodies are joined to one another along all their surfaces, and likewise to the circumference of the vessel, they could not, even if expelled, create a place anywhere if no vacuum existed. Wherefore, in no way would anything from without be introduced into the sphere unless some part of the air previously contained within it were to depart, provided that the whole space is packed and continuous, as they suppose. But if anyone, applying the siphon to his mouth, should wish to blow into the sphere, he will introduce much spirit, although the air that was within it does not depart. Since this is what always happens, it is clearly shown that a contraction of the bodies existing in the sphere occurs into the intermingled vacuums. This contraction, moreover, happens contrary to nature on account of the force of the injection—