GASEOUS SUNLIGHT. 147 



Thus the enormous aggregate of sixty million feet was pro- 

 vided for ; and even this would "not exhaust the supply 

 already existing. Sixty-five to seventy million cubic feet 

 were daily wasting in the Murraysville district alone. 



The aggregate wastage as indicated by data still more re- 

 cent, surpasses all which would be suspected from the facts 

 given above. It is alleged (March, 1886), that in the entire 

 gas field about Pittsburgh, two hundred and sixty-four million 

 cubic feet of gas are daily wasted. One thousand cubic feet 

 are estimated to equal one bushel of coal in heating property. 

 This would make an equivalent of two hundred and sixty- 

 four thousand bushels of coal burned in the air each day. A 

 miner can, on an average, dig seventy bushels of coal a day. 

 The waste then, would be, in round numbers, equal to the 

 daily work of thirty-eight hundred miners or about the whole 

 number employed in the Pittsburgh district. 



This gas is a complex mixture of hydrocarbons. It dif- 

 fers from coal-gas, as also from gas made from petroleum. Its 

 main ingredient is "Marsh gas," which, next to hydrogen, 

 is the lightest substance known, consisting of seventy-five per 

 cent of carbon and twenty-five per cent of hydrogen, and hav- 

 ing a specific gravity of 0.5576, that of air being unity. The 

 mixed natural gas has a specific gravity ranging from 0.51 to 

 0.7. That supplied to Pittsburg may be averaged at 0.6, 

 from which it would appear that the gas for which provision 

 was making in 1884, was equivalent to about forty-nine hun- 

 dred tons of bituminous coal in heating capacity. 



For heating purposes, natural gas excels coal gas thirty- 

 three and one-third per cent. Used in the crude way twenty 

 cubic feet of gas equal one pound of coal. Used in the ordi- 

 nary way, 11.29 cubic feet equal one pound or coal. Used 

 in the most economical way, 8.92 cubic feet equal one pound 

 of coal. For illuminating purposes it possesses only half the 

 value of good coal gas; although it has been asserted of 

 the Fredonia gas that it equals coal gas in respect to intensity 

 of light, and is consumed but half as fast. 



The industrial changes effected in the city of Pittsburgh by 



