A small pamphlet on "Petroleum Gas" has been forwarded to us from Belgium, advocating the use of gas distilled from crude petroleum or from the tarry residues of mineral oils for lighting purposes, particularly in horticultural structures and wherever else the fumes of coal-gas are more than ordinarily obnoxious. According to the showing of the writer, M. L. Jacques, engineer, of Seraing, near Liege, the advantages of petroleum gas are many. The distillatory apparatus required is comparatively small, simple, and cheap. The gas is not more explosive in its nature than ordinary coal-gas. In density it approximates closer to common air than coal-gas, so it is more easily led in any desired direction. It does not foul pipes or burners. It burns with a pure, steady, white flame, with eight times the illuminating power of an equal volume of coal-gas. As mineral oil contains neither sulphur, nitrogen, or oxygen, the gas prepared from it is free from admixtures to which the deleterious effects of coal-gas are due.

The gas burns with about the same amount of heat as coal-gas. Its composition approximates to C4 H4 - that of coal-gas, freed from all impurities, approaching to c2 h4. Carbonic acid is therefore evolved in larger volume than with coal-gas; but as eight times less gas is needed to produce the same amount of light, the heating and deterioration of the surrounding air are proportionately less. A hundred kilogs. (220 lbs.) of crude petroleum give about 2,600 cubic feet, and the same quantity of tarry residue of petroleum 1,900 cubic feet of gas. The gas undergoes no alteration at a pressure of ten atmospheres, so that it is well adapted for storing by compression in portable meters for use in railway trains, etc. M. Jacques states that the town of Seraing, with a population of 26,000, has been lighted for the past eight years with this gas. The apparatus is worked by one man, and supplies 22,000 cubic feet of gas in ten hours, or double that quantity in twenty-four. There are 46,000 feet of pipes; the farthest lamp is 3,300 feet from the works. A certificate from the burgomaster shows that the cost to the town in 1X72 was 2 1/2 centimes per burner per hour, each burner, without reflectors, being equivalent to fourteen wax candles.

The same system was adopted in the city of Neiuport-Bains last year. Very favorable reports have also been received from the large shipbuilding yards of Messrs. Cockerill at Antwerp, and other public and private establishments where the gas has been introduced. Dr. J amain, of the Ophthalmic Institute at Liege, speaks highly in its favor. It gives a very brilliant but very soft flame, he says, which is explained by the large proportion of blue and violet rays, always the coolest and most soothing to the eye, which it contains. No particulars are given of the application of this mode of lighting to horticultural purposes beyond the statement that it has been tried in several large conservatories and found to answer perfectly, and that in one such instance a conservatory with an area of 640 square feet was lighted with ten burners. - Gardeners' Magazine.