[Illustration: Diagram of apparatus as described in text]
The following is the construction of the valve referred to. Take two
rectangular plates of bronze of the thickness of a carpenter’s rule,
and measuring about one finger’s breadth (⁷⁄₁₀ of an inch) on each
side. When these have been accurately fitted to each other, polish
their surfaces so that neither air nor liquid may pass between them.
Let A B C D, E F G H, (fig. 10) be the plates, and in the centre of one
of them, A B C D, bore a circular hole about ⅓ of a finger’s breadth (¼
of an inch) in diameter. Then, applying the side C D to E F, let the
plates be attached by means of hinges, so that the polished surfaces
may come together. When the valve is to be used, fasten the plate A B
C D over the aperture, and any air or liquid forced through will be
effectually confined. For by the pressure exerted the hinges move, and
the plate E F G H opens readily to admit the air or liquid; which when
inclosed in the air-tight vessel, presses on the plate E F G H, and
closes the aperture through which the air was forced in.