Having said thus much of an industry now in its infancy but promising great growth, I submit tables of analyses of common and of the natural or marsh gas, the latter from a paper recently prepared by a committee of the Engineers' Society of Western Pennsylvania, and for the use of which I am indebted to that association:

COMMON GAS.

 Hydrogen 46.0

Light carbureted hydrogen (marsh gas) 39.5

Condensible hydrocarbon 3.8

Carbonic oxide 7.5

" acid 0.6

Aqueous vapor 2.0

Oxygen 0.1

Nitrogen 0.5

-----

100.0 

Natural gas is now conveyed to Pittsburg through four lines of 5-5/8 inch pipe and one line of eight inch pipe. A line of ten inch pipe is also being laid. The pressure of the gas at the wells is from 150 to 230 pounds to the square inch. As the wells are on one side eighteen and on the other about twenty-five miles distant, and as the consumption is variable, the pressure at the city cannot be given. Greater pressure might be obtained at the wells, but this would increase the liability to leakage and bursting of pipes. For the prevention of such casualties safety valves are provided at the wells, permitting the escape of all superfluous gas. The enormous force of this gas may be appreciated from a comparison of, say, 200 pounds pressure at the wells with a two ounce pressure of common gas for ordinary lighting. The amount of natural gas now furnished for use in Pittsburg is supposed to be something like 25,000,000 cubic feet per day; the ten inch pipe now laying is estimated to increase the supply to 40,000,000 feet.

The amount of manufactured gas used for lighting the same city probably falls below 3,000,000 feet.

About fifty mills and factories of various kinds in Pittsburg now use natural gas. It is used for domestic purposes in two hundred houses. Its superiority over coal in the manufacture of window glass is unquestioned. That it is not used in all the glass houses of Pittsburg is due to the fact that its advantages were not fully known when the furnaces were fired last summer, and it costs a large sum to permit the furnaces to cool off after being heated for melting. When the fires cool down, and before they are started up again, the furnaces now using coal will doubtless all be changed so as to admit natural gas. The superiority of French over American glass is said to be due to the fact that the French use wood and the Americans coal in their furnaces, wood being free from sulphur, phosphorus, etc. The substitution of gas for coal, while not increasing the cost, improves the quality of American glass, making it as nearly perfect as possible.

While the gas is not used as yet in any smelting furnace nor in the Bessemer converters, it is preferred in open hearth and crucible steel furnaces, and is said to be vastly superior to coal for puddling. The charge of a puddling furnace, consisting of 500 pounds of pig-metal and eighty pounds of "fix," produces with coal fuel 490 to 500 pounds of iron. With gas for fuel, it is claimed that the same charge will yield 520 to 530 pounds of iron. In an iron mill of thirty furnaces, running eight heats each for twenty-four hours, this would make a difference in favor of the gas of, say, 8 x 30 x 25 = 6,000 pounds of iron per day. This is an important item of itself, leaving out the cost of firing with coal and hauling ashes.

For generating steam in large establishments, one man will attend a battery of twelve or twenty boilers, using gas as fuel, keep the pressure uniform, and have the fire room clean as a parlor. For burning brick and earthenware, gas offers the double advantage of freedom from smoke and a uniform heat. The use of gas in public bakeries promises the abolition of the ash-box and its accumulation of miscellaneous filth, which is said to often impregnate the "sponge" with impurities.

In short, the advantages of natural gas as a fuel are so obvious to those who have given it a trial, that the prediction is made that, should the supply fail, many who are now using it will never return to the consumption of crude coal in factories, but, if necessary, convert it or petroleum into gas at their own works.

It seems, indeed, that until we shall have acquired the wisdom enabling us to conserve and concentrate the heat of the sun, gas must be the fuel of the future.--Popular Science Monthly.

 TABLE OF ANALYSIS OF NATURAL GAS--FROM VARIOUS SOURCES.

_____________________________________________________________________

| | | | | | | |

| CONSTITUENTS | [2.] | [3.] | [6.] | [7.] | [8.] | [9.] |

|_______________|________|________|________|________|________|_________

| | | | | | | |

| Hydrogen | .... | .... | 6.10 | 13.50 | 22.50 | 4.79 |

| | | | | | | |

| Marsh Gas | 82.41 | 96.50 | 75.44 | 80.11 | 60.27 | 89.65 |

| | | | | | | |

| Ethane | .... | .... | 18.12 | 5.72 | 6.80 | 4.39 |

| | | | | | | |

| Propane | .... | .... | trace. | .... | .... | trace. |

| | | | | | | |

| Carbonic acid | 10.11 | .... | 0.34 | 0.66 | 2.28 | 0.35 |

| | | | | | | |

| Carbonic oxide| .... | 0.50 | trace. | trace. | trace. | 0.26 |

| | | | | | | |

| Nitrogen | 4.31 | .... | .... | .... | 7.32 | .... |

| | | | | | | |

| Oxygen | 0.23 | 2.00 | .... | .... | 0.83 | .... |

| | | | | | | |

| "Illuminating | 2.94 | 1.00 | .... | .... | .... | 0.56 |

| hydrocarbons."|________|________|________|________|________|________|

| | | | | | | |

| | 100.00 | 100.00 | 100.00 | 99.99 | 100.00 | 100.00 |

|_______________|________|________|________|________|________|________|

| |

| Specific gravity 0.693 0.692 0.6148 0.5119 0.5580 |

|_____________________________________________________________________|

______________________________________________________________________

| | | | | | | |

| CONSTITUENTS | [10.] | [12.] | [14.] | [15.] | [16.] | [17.] |

|_______________|________|________|________|________|________|_________

| | | | | | | |

| Hydrogen | .... | 19.56 | .... | 0.98 | .... | .... |

| | | | | | | |

| Marsh Gas | 96.34 | 78.24 | 47.37 | 93.09 | 80.69 | 95.42 |

| | | | | | | |

| Ethane | .... | .... | .... | .... | 4.75 | .... |

| | | | | | | |

| Propane | .... | .... | .... | .... | .... | .... |

| | | | | | | |

| Carbonic acid | 3.64 | .... | 3.10 | 2.18 | 6.44 | 0.60 |

| | | | | | | |

| Carbonic oxide| | .... | .... | .... | .... | .... |

| | | | | | | |

| Nitrogen | | .... | 49.39 | 0.49 | 8.12 | 3.98 |

| | | | | | | |

| Oxygen | | 2.20 | 0.17 | .... | .... | .... |

| | | | | | | |

| "Illuminating | [10.] | .... | .... | 3.26 | .... | .... |

| hydrocarbons."|________|________|________|________|________|________|

| | | | | | | |

| | | 100.00 | 100.03 | 100.00 | 100.00 | 100.00 |

|_______________|________|________|________|________|________|________|

| |

|Specific gravity 0.5923 0.56 |

|_____________________________________________________________________| 
Petroleum is composed of about 85 per cent of carbon and 15 per cent of nitrogen.
Locations:
1. Petrolia, Canada. 2. West Bloomfield, N.Y. 3. Olean, N.Y. 4. Fredonis, N.Y. 5. Pioneer Run, Venango Co., Pa. 6. Burn's Well, near St. Joe., Butler Co., Pa. 7. Harvey Well, Butler Co., Pa. 8. Cherry Tree, Indiana Co., Pa. 9. Leechburg, Pa. 10. Creighton, Pa. 11. Penn Fuel Co.'s Well, Murraysville, Pa. 12. Fuel Gas Co.'s Well, Murraysville. 13. Roger's Gulch, Wirt Co., W. Va. 14. Gas from Marsh Ground 15. Baku, on the Caspian Sea. 16. Gas occluded in Wigan cannel-coal. 17. Blower in coal-mine. South Wales.
Notes:
1. Chiefly marsh-gas with ethane and some carbonic acid. 4. A mixture of marsh-gas, ethane and butane. 5. Chiefly propane, with small quantities of carbonic acid and nitrogen. 10. Trace of heavy hydrocarbons. 11. Marsh-gas, with a little carbonic acid. 13. Chiefly marsh-gas, with small quantities of nitrogen and 15.86 per cent carbonic acid.
References:
1. Fouqué, "Comptes Rendus," lxvii, p. 1045. 2. H. Wurtz, "Am. Jour. Arts and Sci." (2), xlix, p. 336. 3. Robert Young. 4. Fouqué, "Comptes Rendus," lxvii. p. 1045. 5. Fouqué, "Comptes Rendus," lxvii. p. 1045. 6. S.P. Sadler, "Report L, 2d Geol. Sur. Pa.," p. 153. 7. S.P. Sadler, "Report L, 3d Geol. Sur. Pa.," p. 152. 8. S.P. Sadler, "Report L, 3d Geol. Sur. Pa.," p. 153. 9. S.P. Sadler, "Report L, 3d Geol. Sur. Pa.," p. 153. 10. F.C. Phillips. 11. Robert Young. 12. Rogers. 13. Fouqué, "Comptes Rendus," lxvii, p. 1045. 14. Bischof's Chemical Geology," I, p. 730. 15. Bischof's Chemical Geology," I, p. 730. 16. J.W. Thomas, London, "Chemical Society's Journal," 1876, p. 793. 17. Same, 1875, p. 793.