[Illustration: Diagram of apparatus as described in text]
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), containing 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 a 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
O, 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.