long box supplied with air under pressure from
the bellows and containing the valves (called _pallets_) controlling
the access of the wind to the pipes. Between the pallet and the foot
of the pipe comes another valve called the _slider_, which controls the
access of the wind to the whole row of pipes or stop. The pallet is
operated from the keyboard by the _key action_. Every key on the
keyboard has a corresponding pallet in the wind-chest, and every
stop-knob operates a slider under the pipes, so that both a slider must
be drawn and a pallet depressed before any sound can be got from the
pipes. The drawings will make this plain.

Fig. 1 is a front view and Fig. 2 a side view of the wind-chest. A is
the wind-chest into which compressed atmospheric air has been
introduced, either through the side or bottom, from the end of the
wind-trunk B. The pallets, C C C, are held against the openings, D D
D, leading from the wind-chest to the mouth of the pipes, by springs
underneath them.

[Illustration: Fig. 1. The Wind-chest. Front View]

The spring S (Fig. 2) keeps the pallet C against the opening into D.
The wires called _pull-downs_ (P, P, P), which pass through small holes
in the bottom of the wind-chest and are in connection with the
keyboard, are attached to a loop of wire called the _pallet-eye_,
fastened to the movable end of the pallet. A piece of wire is placed
on each side of every pallet to steady it and keep it in the
perpendicular during its ascent and descent, and every pallet is
covered at top with soft leather, to make it fit closely and work
quietly. When P is pulled down (Fig. 1) the pallet C descends, and air
from the wind-chest A rushes through D into the pipe over it. But the
slider _f_ is a narrow strip of wood, so placed between the woodwork
_g_ and _h_ that it may be moved backwards and forwards from right to
left, and is pierced with holes corresponding throughout to those just
under the pipes. If the apertures in the slider are under the pipes,
the opening of a pallet will make a pipe speak; if, however, the slider
has been moved so that the apertures do not correspond, even if the
pallet be opened and the chest full of air from the trunks, no sound
will be produced.

[Illustration: Fig. 2. The Wind-chest. Side View]

When the apertures in the slider are under those below the pipe, the
"stop," the handle of which controls the position of the slider, is
said to be _out_, or _drawn_.