No. 73. A Lamp in which the Oil is raised by Water, as required.
THE construction of a lamp. * * * * ** ** Underneath the lamp place a vessel perfectly air-tight, A B (fig. 73), either attached to the lamp or distinct from it. From this let two tubes extend, C D, E F, communicating with the vessel; the extremity C must reach to the bottom except a space sufficient for the passage of water and the tube C D to the surface of the lamp, having at the extremity D a small cup through which the water is to be poured in: the tube E F must pass, air-tight, through the bottom of the lamp. Now if oil be poured through the opening, it will first pass into the vessel A B, and then, when A B is full, the tubes C D, E F, and the lamp will be filled also. As the lamp burns it will become empty, and if we pour in water through the cup, it will pass into the vessel A B, and the oil will ascend and fill up the deficiency in the lamp, until it reaches the lamp-nozzle. When the oil has sunk again, we must do the same, repeating it till the supply is expended. If it is required to remove the vessel A B, the oil being retained in the lamp, there must be a valve or tap in the pipes C D, E F, close to the vessel A B, with keys near the lamp, so that when the keys are turned, the oil in the lamp, and that in the tubes, shall be confined. Thus the vessel may be removed from the lamp, and, whenever it is desired, we may bring them together again, and open the keys. It is better that the pipe E F should lead to the handle of the lamp, and C D a little behind it, having the cup which communicates with it, and through which water will be poured in, placed above; so that the oil will flow from the handle at the same time that the water is poured into the cup.