a vessel containing oil, with a lighted wick.

Dr. St. Clair, in Phil. Trans. no 245, gives the description of an improvement upon the common lamp. He proposes that it should be made two or three inches deep, with a pipe coming from the bottom almost as high as the top of the vessel; let it be filled so high with water as to cover the hole of the pipe at the bottom, that the oil may not get in at the pipe, and so be lost. Then let the oil be poured in, so as to fill the vessel almost brim full, which must have a cover pierced with as many holes as there are wicks designed. When the vessel is thus filled, and the wicks are lighted, if water falls in by drops at the pipe, it will always keep the oil at the same height, or very near; the weight of the water being to that of the oil as 20 to 19, which in two or three inches makes no great difference. If the water runs faster than the oil wastes, it will only run over at the top of the pipe, and what does not run over will come under the oil, and keep it at the same height.