“If the cock be so arranged as to present its key upon the top of the pedestal, and if to the key there be adapted a statuette representing a man armed with a club, things may be so arranged that the animal shall drink when the man has his back turned, for example, and that he shall stop drinking when the man threatens him with the club.
“The following is the way in which a knife may be passed through the animal’s neck without causing the head to fall or interrupting communication between the mouth and pedestal. The head and body form two distinct pieces, which are adjusted according to the plane, O P ([Figs. 1], [2, and 3]). The tube, M N, is interrupted to the right of this slit, and the two parts of it are connected by a smaller tube, α β, which enters by slight friction into the interior of each of them; and to this small tube, α β, there are fixed two racks, δ and ε. Above δ and under ε are placed two segments of toothed wheels, π and ρ, which are movable around axles fixed in the body of the animal. Over the whole there is a third wheel, which is likewise movable around an axle fixed in the animal’s body, and the thickness of which keeps increasing from the centre to the circumference. This wheel is cut out into three parts of circles, μ, ν, and ξ, which have for diameters three of the sides of the inscribed hexagon. It is inclosed in the neck in such a way that the circular cavity containing it embraces just four of the sides of the inscribed hexagon, the two other sides projecting outside of the plane, O P. In the piece that forms the head a circular cavity is formed capable of containing this projecting portion of the wheel, and a wedge-shaped profile is given it, so that when one tooth of the wheel, σ, is engaged therein by the edge, it can also only leave it by the edge. Let us now suppose the wheel, σ, free; let us engage one of its teeth in the cavity, χ ψ; let us cause the head and body to approach; let us fix the wheel, σ, in the body by means of the movable axle traversing it; and let us introduce a knife into the slit, O P, and see what will happen.
HERON’S DECAPITATED DRINKING HORSE.
“The blade, on entering the space, ξ, will press against one of the teeth, and cause it to descend until it, as well as the knife, is disengaged. The tooth above the space, ξ, will then be disengaged in its turn and connect the head with the body again. The knife-blade, which is now under the wheel, σ, rests on the inclined plane that the figure shows in the segment, π, and, on pressing thereupon, causes the wheel to turn, and with it the rack, δ, and the tube, α β, which latter leaves the tube, M, and gives passage to the blade between it and the extremity, α. Then the blade comes in contact with the lower projection of the sector, ρ, which has been carried upward by the motion of the rack, ε, that is connected with the rack, δ. On pressing against such projection the blade causes the segment, ρ, to revolve in a contrary direction, brings ε toward the left, and causes the small tube, α β, to enter anew the tube, M. Communication between M and N is thus reëstablished.”
M. de Rochas has never found elsewhere than in the “Pneumatics” a description of this system of toothed wheels, although he has read the majority of books treating of this class of ideas. The description given by Heron is itself so confused and so mutilated, and the figure that accompanies it is so incomplete, that in all the Latin editions it is suppressed as incomprehensible.
THE DECAPITATED HORSE. DETAILS OF THE MECHANISM IN THE NECK.