The sound of a trumpet may be produced on the opening of the doors of a temple. The following is the construction.
Behind the door let there
be a vessel, A B C D (fig. 17), containining water. In this invert a
narrow-necked vessel, shaped like an extinguisher, F, with which, at its
lower extremity, let a trumpet, H K, communicate, provided with bell and
mouthpiece. Parallel with the tube of the trumpet, and attached to it,
let the rod L M run, fastened, at the lower end, to the vessel F, and
having at the other extremity al loop, M: through this loop let the beam
N X pass, thus supporting the vessel F, at a sufficient height above the
water. The beam N X must turn on the pivot 0, and a chain or cord,
attached to the extremity X, be fastened, by means of the pulley, P, to
the hinder part of the door. When the door is opened, the cord will be
stretched, and draw upwards the extremity X of the beam, so that the
beam N X no longer supports the loop M; and when the loop changes its
position in consequence, the vessel F will descend into the water, and
give forth the sound of a trumpet by the expulsion of the air contained
in it through the mouthpiece and bell.