Daniel detected the imposture in a very original manner. He caused ashes to be sifted upon the floor of the temple, whereby the footsteps of the false priests were made manifest to the enraged King of Babylon. {5} One reads in Pausanias (_Arcadia_, 1 VIII, Ch. xvi) that at Jerusalem the sepulcher of a woman of that country, named Helena, had a door which was of marble like the rest of the monument, and that this door opened of itself on a certain day of the year, and at a certain hour, by means of concealed machinery, thus antedating our time-locks. Eventually it closed itself. “At any other time,” adds the author, “if you had desired to open it, you would have more easily broken it.” When Aeneas went to consult the Cumæan Sibyl, the hundred doors of the sanctuary opened of themselves, in order that the oracle might be heard. “Ostia jamque domus patuere ingentia centum Sponte sua, vatisque ferunt responsa per auras.” [Illustration: APPARATUS FOR BLOWING A TRUMPET ON OPENING A DOOR.] According to Pliny, the doors of the labyrinth of Thebes were constructed in such a manner that when they were opened a sound resembling that of thunder greeted the astonished worshipers. Heron, in his _Pneumatics_, describes an apparatus for blowing a trumpet on opening the door of a temple, the effect of which must have been awe inspiring to the uninitiated common people. It is hardly necessary to give a detailed translation of the text of the Greek engineer, as the _modus operandi_ of the experiment is sufficiently explained by reference to the descriptive {6} picture. It will suffice to add: One sees that when the door of the temple is opened, a system of cords, rods and pulleys causes a hemispherical cap, to the upper part of which the trumpet is attached, to sink into a vase full of water. The air compressed by the water escapes through the instrument, causing it to sound. [Illustration: MECHANISM WHICH CAUSED THE TEMPLE DOORS TO OPEN WHEN A FIRE WAS LIGHTED ON THE ALTAR.] Another remarkable device is described in the _Pneumatics_ of Heron, and consists of an apparatus which is entitled: “_Construction of a chapel wherein, when fire is lighted upon the altar, the doors open, and when it is extinguished, they close_.” {7} The altar is hollow, and when a fire is lighted thereon, the air contained in the interior expands and begins to press upon the water with which the globe situated beneath is filled. The water then rises through a bent tube which leads to a species of pot, into which it falls. The pot is suspended upon a cord which passes along a pulley, doubling immediately, in order to enroll itself about two cylinders, which turn upon pivots, said cylinders forming the prolongation of the axes upon which the doors above turn. Around the same cylinders are enrolled in a contrary manner, two other cords, which also unite into one before passing along a pulley, and then hanging vertically for the support of a counterpoise.