character of the oil, the yield of illuminating oil can be increased, but a residuum is always left in the large stills to be afterward treated in smaller ones.
S. D. Hayes states that this operation can be reversed, and from two to ten per cent. of a heavy oil obtained from the lightest and cheapest gasolene or petroleum naphtha. This change he observed in an apparatus constructed by Mr. Z. A. Willard, for generating gases and hydrocarbon vapors for metallurgical purposes. It consisted essentially of upright wrought-iron cylinders, half-full of the naphtha, through which steam at the ordinary working temperature and pressure passed, vaporizing the naphtha, and maintaining a pressure of about fifty pounds to the inch. The steam and naphtha vapors were thus kept above the liquid at a temperature much above the boiling-point of naphtha, but never as high as 300° Fahr., and the decompositions appeared to occur rather in the vapors than in the liquid. The heavy oil drawn off below had a dark yellowish-brown color, was nearly odorless after a few days' exposure to the air, had a specific gravity of about 34° Beaumé, and boiled above 400° Fahr. By redistilling, it was broken up into lighter and heavier liquid hydrocarbons, paraffine, and separated carbon (American Journal of Science, III., ii., 184).
Petroleum as a Fuel and Gas-Producer.—The use of gasolene in gas-machines is well known, and sometimes naphtha has been used to enrich coal-gas, by decomposing its vapor at a cherry-red heat, so as to produce a gas rich in heavy hydrocarbons, which is mixed with the coal-gas. Crude petroleum has also been conducted continuously into red-hot cast-iron retorts, whereby it is decomposed and rich gas formed. The Lowe process, now making daily 120,000 cubic feet of gas, of 19.5 candle-power, for a five-foot burner, at Utica, New York, is very successful. It consists essentially in forcing steam through a generator partly full of anthracite coal, brought to intense ignition; the steam is decomposed, and the resulting hydrogen meets crude petroleum that trickles down through the top of the generator; the petroleum is carried in vapor with the hydrogen into a "superheater" filled with loose fire-bricks, previously intensely heated by the gases from the generator. Here the hydrogen and hydrocarbons react upon each other, producing a permanent gas, which is purified as usual. The resulting gas is of uniform quality, very pure, and the saving in labor and materials is about 35 per cent. over coal-gas (Scientific American, January 8, 1876).
As regards the use of petroleum for fuel, it has always been found difficult to secure the complete combustion of the oil, so as to avoid smoke; the complicated nature of the contrivances devised for its use has also worked against its introduction as a fuel; but a furnace for reheating and rolling scrap-iron into boiler-plate has been invented by C. J. Eames, and is worked in Jersey City, which deserves mention. Prof. H. Wurtz (American Chemist, September, 1875) has de-
