Let _ΑΒΓ_ (Fig. 1) be a cupping glass (like that which is usually applied to the skin), divided by a partition, _ΔΕ_. Through the bottom let there be passed two tubes that slide one within the other by friction--_ΖΗ_ being the external and _ΘΚ_ the internal one. In these two tubes, external to the glass, there are two apertures, _ΛΜ_, that face each other. The extremities of the tubes situated within the apparatus should be open, and the external extremity of _ΘΚ_ should be closed and provided with a key. Beneath the partition, _ΔΕ_, there is another cock, _ΝΞ_, like the one just described, save that the corresponding apertures are within the cupping-glass, and are in communication with an aperture in the partition, _ΔΕ_. "Things being arranged thus, the keys of the cock are revolved in such a way that the apertures of the one at the bottom of the instrument are in a line with each other, while the cock above the partition remains closed, inasmuch as its apertures do not correspond. The chamber, _ΔΓ_, being full of air, if we apply the mouth to the orifices, _ΛΜ_, and suck out a portion of the air, and turn the key of the cock without removing the mouth from the tube, we shall be able to thus keep up a rarefaction of the air in the chamber, _ΓΔ_. The oftener we perform this operation, the more air we shall remove. Let us now apply the cupping-glass to the skin in the usual way, and open the cock, _ΝΞ_, by turning the key. A portion of the air contained in _ΑΔΕ_ will pass into _ΓΔ_, and we shall then see the skin, as well as the subjacent matters that pass through its interstices, that we call unexplored spaces, drawn into the space in which the air is rarefied." As for the pressure fountain, this had reached perfection as long ago as the Alexandrine epoch. The following description of it is borrowed from the "Pneumatics:" "_To construct a hollow sphere, or any other vessel, in which, if a liquid be poured, the latter may be made to rise spontaneously with great force so as to empty the vessel, although such motion be contrary to nature_."