e produced. Were twenty large
Diapasons added to the instrument in Ocean Grove, N. J., or to that in
the Baptist Temple, Philadelphia, and were the Diaphone removed, the
instrument would suffer most seriously. In the Pedal department no
reed or flue pipe can begin to compare with a Diaphone, either in
attack or in volume of tone.

In Figure 23 we give a sectional view of the first large Diaphone made,
namely that constructed for the Hope-Jones organ in Worcester
Cathedral, Eng., 1896.

[Illustration: Fig. 23. Diaphone in Worcester Cathedral, Eng.]

M is a pneumatic motor or bellows to which is attached a rod bearing
the compound and spring valve V, V|1|, working against the spring S.
On the admission of wind (under pressure) to the box A, the motor M is
caused to collapse, and thereby to open the valves V, V|1|. Wind then
rushes into the chamber B, and entering the interior of motor M through
the passage C, equalizes the pressure in the motor. The action of the
springs now serves to close the valves V, V|1|, and to open out the
motor M, whereupon the process is repeated.

[Illustration: Fig. 24. Diaphone in Aberdeen University.]

In Fig. 24 we illustrate the Diaphone in the Hope-Jones organ built for
Aberdeen University, Scotland. The action is as follows:

Wind from the organ bellows enters the pipe foot F, and raises the
pressure in the chamber C. The air in the chamber will press upon the
back of the valve V, tending to keep it closed. It will press also
upon the bellows or motor M, and as this bellows has a much larger area
than that of the valve, it will instantly collapse, and, through the
medium of the tail piece T, will pull the valve V off its seat and
allow the compressed air in the chamber C to rush into the resonator or
pipe P. Owing to the inertia of the column of air contained in the
pipe P, a momentary compression will take place at the lower end of the
pipe, and the pressure of the air inside the motor M will, in
consequence, be raised. The motor having now increased pressure both
sides, will no longer keep the valve off its seat, and the spring S
will open the motor and close the valve. The compression caused by the
admission of the puff of air into the lower parts of the pipe P will be
followed by the usual rarefaction, and as this rarefaction will exhaust
or suck the air from the inside of the motor M, the valve will again be
lifted from its seat, and the cycle of operations will be