[Larger plate.]

[1648]. Double-beat valve, with sunk seating.

[1649]. Common D slide valve, with three ports.

[1650]. Duplex or double D slide.

[1651]. Another form, partly in equilibrium.

[1652]. Equilibrium slide valve, with circular packed trunk on back, of area sufficient to balance the face area of valve.

[1653]. Similar result obtained by a piston and link.

[1654]. Equilibrium piston valve employed in lieu of the slide valve. A steam pipe, B B exhaust.

[1655]. Gridiron slide valve.