“Let us now remove the lamp and fill the vessel with oil by the aid of the tube, Ξ Ο. The air will escape through the tube, Μ Ν, and afterward through a cock which is open near the bottom, Γ Δ, when the water has flowed out from the compartment, Γ Δ Ε Ζ. Let us place the lamp upon its base, connecting it at the same time with the tube, Π. When it becomes necessary to pour oil into it, we will open the cock near the partition, Ε Ζ. The water that is in the compartment, Γ Δ Ε Ζ, as well as the air therein, being forced through the tube, Μ Ν, into the vessel, will cause the oil to rise and pass into the lamp through the tube, Ξ Ο, and the one that forms a continuation of it. When it is desired to cause the oil to stop coming over, the cock is closed, when the flow will cease. This may be repeated as often as may be necessary.”
Such was, perhaps, Plato’s lamp, of which Athenæus speaks in the “Banquet of the Sophists,” and by means of which the illustrious philosopher was enabled to have a light for himself during the longest nights in the year.
AN ANCIENT AUTOMATON.
In his “Spiritalia” (written about 150 B.C.) Heron describes several automata of which figures of birds form a part; but perhaps the most remarkable for its ingenious simplicity is No. 44, the [illustration] of which we reproduce.
The description of this, as given by Heron, is somewhat meager and unsatisfactory, but the [drawing] is so very plain that, taken in connection with other mechanism in his work, operated in a similar way, it is easy to understand how the desired result was accomplished.
An air-tight box of metal was provided, which was divided into four compartments, 1, 2, 3, 4, by horizontal diaphragm plates. On the top of this box was a basin, O, for receiving the water of a fountain. Around this basin were four birds, A, B, C, D, perched upon branches or shrubs, which apparently grew out of the top of the box. Each of these branches was hollow, and communicated with one of the compartments already named, by one of the pipes, 9, 10, 12, and 13, which passed but a very short distance through the tops of the several compartments. The bodies of the birds were also hollow, and were connected with the hollow branches by tubes in their legs. In the hollow body of each bird were two musical reeds or whistles of different note. One of these would sound when air was forced outward through the beak of the bird, and the other would only respond to air drawn inward. This alternate action of the air, and consequent variation of note, was produced by the peculiar way in which the water supplied by the fountain was made to pass through the several compartments.
The water from the basin, O, entered compartment 1 near its bottom by the pipe 11, and as it rose in the compartment, it compressed the air above it, which escaped through the beak of the bird, A, and caused its first note to sound; but when the water reached the top of the bend of the siphon 5, it at once began to discharge by that siphon into compartment 2; but as the siphon 5 was so proportioned that it discharged the water much faster than it was supplied by pipe 11, the level of the water in compartment 1 gradually fell, and the air in passing into this compartment through the beak of the bird, A, caused its second note to sound. As the water rose in compartment 2, it compressed the air above it, which passed by the pipe 10, to the bird, B, which then sounded its first note, while the bird, A, was sounding its second, and this state of affairs continued until all of the water was discharged from the compartment 1, and compartment 2 was filled to the top of the bend of siphon 6, which then began to discharge into compartment 3; and as siphon 5 had ceased to operate, the water gradually fell in compartment 2, and the air entering by the beak of the bird, B, sounded its second note. While this was taking place, compartment 1 was again filling, and the first note of bird, A, sounding; and compartment 3 was also filling, and the air above the water therein was being forced by the pipe 12 into the bird, C, and causing its first note to sound.
