[Illustration: FIG. 2.--MARVELOUS ALTAR (According to Heron).]

Finally, the crowns and garlands that suddenly made their appearance on
the four faces of the base of the stage were hidden there in advance
between the two walls surrounding the base. The space thus made for the
crowns was closed beneath, along each face, by a horizontal trap moving
on hinges that connected it with the inner wall of the base, but which
was held temporarily stationary by means of a catch. The crowns were
attached to the top of their compartment by cords that would have
allowed them to fall to the level of the pedestal, had they not been
supported by the traps.

At the desired moment, the catch, which was controlled by a special
cord, ceased to hold the trap, and the latter, falling vertically, gave
passage to the festoons and crowns that small leaden weights then drew
along with all the quickness necessary.

Two points here are specially worthy of attracting our attention, and
these are the flow of wine or milk from the statue of Bacchus, and
the spontaneous lighting of the altar. These, in fact, were the two
illusions that were most admired in ancient times, and there were
several processes of performing them. Father Kircher possessed in his
museum an apparatus which he describes in _Oedipus Egyptiacus_ (t. ii.,
p. 333), and which probably came from some ancient Egyptian temple.
(Fig. 1.)

It consisted of a hollow hemispherical dome, supported by four columns,
and placed over the statue of the goddess of many breasts. To two of
these columns were adapted movable brackets, at whose extremities there
were fixed lamps. The hemisphere was hermetically closed underneath by a