USE OF THE NAPHTHA FOR ILLUMINATION Many fruitless experiments have been made in the course of this investigation which it is needless to recount. I will, therefore, only state those results which are of value.
i. I have found that the only lamp in which this oil can be successfully burned is the camphene lamp, or one having a button to form the flame, and an external cone to direct the current of air, as is now usual in all lamps designed to burn either camphene, rosin oil, sylvic oil, or any other similar product.
2. As the distilled products of petroleum are nearly or quite insoluble in alcohol, burning fluid (i. e., a solution of the oil in alcohol) cannot be manufactured from it.
3. As a consequence, the oil cannot be burned in a hand lamp, since, with an unpro tected wick, it smokes badly. Neither can it be burned in a Carcel's mechanical lamp, because a portion of the oil being more volatile than the rest, rises in vapour on the elevated wick required in that lamp, and so causes it to smoke.
I have found all the products of distillation from the copper still capable of burning well in the camphene lamp, except the last third or fourth part (i.e., that portion which came off at 700° F. and rising, and which was thick with the crystals of paraffine). Freed from acidity by boiling on water, the oils of this distillation burned for twelve hours without injuriously coating the wick, and without smoke. The wick may be elevated considerably above the level required for camphene, without any danger of smoking, and the oil shows no signs of crusting the wick tubes with a coating of rosin, such as happens in the case of camphene, and occasions so much inconvenience.
The light from the rectified naphtha is pure and white, without odour. The rate of consumption is less than half that of camphene, or rosin oil. The Imperial pint, of 20 fluid ounces, was the one employed—a gallon contains I 6o such ounces. A camphene lamp, with a wick one inch thick, consumed of rectified naphtha in one hour, if ounces of fluid. A Carcel's mechanical lamp of I-inch wick, consumed of best sperm oil, per hour, 2 ounces. A "Diamond Light" lamp, with "sylvic oil," and a wick ri-inch diameter, consumed, per hour, 4 ounces.
I have submitted the lamp burning petroleum to the inspection of the most ex perienced lampists who were accessible to me, and their testimony was, that the lamp burning this fluid gave as much light as any which they had seen, that the oil spent more economically, and the uniformity of the light was greater than in camphene, burning for twelve hours without a sensible diminution, and without smoke. I was, however, anxious to test the amount of light given, more accurately than could be done by a comparison of opinions. With your approbation I proceeded therefore to have constructed a photometer, or apparatus for the measurement of light, upon an improved plan. Messrs. Grunow, scientific artists of this city, undertook to construct this apparatus, and have done so to my entire satisfaction. This apparatus I shall describe elsewhere—its results only are interesting here. By its means I have brought the petroleum light into rigid comparison with the most important means of artificial illumination. Let us briefly recapitulate the results of these