The first locomotive, or self-moving vehicle, of which we have any account was this invention of Heron of Alexandria. In his work just cited descriptive of automatic or self-moving machines, there is illustrated the mechanism by which the shrine of Bacchus, mounted upon three wheels concealed within its base, is moved. [Fig. 3] is a vertical section of that part of the shrine below the canopy, and exhibits the propelling apparatus of this ancient locomotive machine. Within the base are seen two of the supporting wheels; the driving wheel nearest the eye having been removed. On the axle of the driving wheels was the drum, b, about which was wound the rope, a, which passed upward through the space on one side of the shrine and over the pulleys, r r, and was fastened to the ring, c, of the ponderous lead weight, d, which rested upon a quantity of dry, fine sand. The escape of this sand through a small hole in the middle of the floor of the compartment containing it allowed the lead weight, d, to gradually descend, and by pulling upon the cord, a, caused the shrine to move slowly forward in a straight line.
FIG. 5.
Heron describes the method of arranging and proportioning the wheels in case it was desired that the shrine move in a circular path. He also shows how the shrine can be constructed to move in straight lines at right angles to each other.
[Fig. 4] shows the arrangement of the wheels for this purpose, and [Fig. 5] is a perspective view, showing the screws by which the bearings of either set of wheels could be raised or lowered, so as to cause the shrine to move in the way proposed.
Supposing the motive cords properly wound around vertical bobbins, instead of a horizontal one, and we have the half revolution of Bacchus and Victory, as well as the complete revolution of the Bacchantes. This is clearly shown in the engraving ([Fig. 2]).
The successive lighting of the two altars, the flow of milk and wine, and the noise of drums and cymbals were likewise obtained by the aid of cords moved by counterpoises, and the lengths of which were graduated in such a way as to open and close orifices at the proper moment, by acting through traction on sliding valves which kept them closed.
Small pieces of combustible material were piled up beforehand on the two altars, the bodies of which were of metal, and in the interior of which were hidden small lamps that were separated from the combustible by a metal plate which was drawn aside at the proper moment by a small chain. The flame, on traversing the orifice, thus communicated with the combustible.