ent or swing, the speed of its vibration, and consequently the
pitch of the note emitted, will be governed by the length of the
resonator or pipe R.

The tone given by this particular form of Diaphone possesses a peculiar
sweetness in quality, while the power is limited only by the pressure
of air used to operate it.

[Illustration: Fig. 28. Diaphone in the Auditorium, Ocean Grove, N. J.]

In Fig. 28 we give an illustration of the form of Diaphone used in the
Hope-Jones Unit organ at the Auditorium, Ocean Grove, N. J.

P is a pallet controlling the admission of air into the body of the
pipe P|1|. M is a motor adapted for plucking open the pallet P through
the medium of strap _s_. The box B is permanently supplied with air
under pressure from the bellows. When the valves V and V|1| are in the
position shown in the drawing, the Diaphone is out of action, for the
wind from the box B will find its way through the valve V (which is
open) into the interior of the motor M.

When it is desired to make the note speak, the small exterior motors
M|1| and M|2| are simultaneously inflated by the electro-pneumatic
action operated by depressing the pedal key. The valve V will
thereupon be closed and the valve V|1| be opened. As the pressure of
air inside the motor M will now escape into the pipe or resonator P|1|,
the motor will collapse and the pallet P will be opened in spite of the
action of the spring S which tends to keep it closed.

The wind in the box B will now suddenly rush into the lower end of the
pipe P|1|, and by causing a compression of the air at that point will
again raise the pressure of the air inside the motor M. The pallet
will thereupon close and the cycle of operations will be repeated--thus
admitting a series of puffs of wind into the foot of the pipe P|1| and
thereby producing a musical tone of great power.

As the valve V|1| is open, the sound waves formed in the pipe P|1| will
govern the speed of vibration of the motor M. It will thus be obvious
that the Diaphone will always be in perfect tune with the resonator or
pipe P|1|, and that the pitch of the note may be altered by varying the
length of the pipe.

[Illustration: Fig. 29. Diaphone in St. Paul's Cathedral, Buffalo, N.
Y.]

In Fig. 29 will be found an illustration of the Diaphone (or valvular
reed) used in the Hope-Jones organ at St. Paul's Cathedral, Buffalo, N.
Y.

Upon depressing a key, wind is admitted into the box B. Pressing