NATURAL PHILOSOPHY. 155 



0.0575-7-550 = 0.0001046, about one-tenth of a mill per hour per 

 candle, being about one-tenth the cost of gas light. 



Let us for a moment take another view of the matter. The 

 average hourly consumption of coal by a good steam engine may 

 be set down at 4 pounds per hour per horse-power, (83,000 X 

 60) -4-4 = 495, 000 foot-pounds from 1 pound of coal. Utilizing 

 as electricity, and thence light, one-fourth part of this, we get 



123,750 



495,000 -=-4 =123,750 foot-pounds, or as light,- - = 137.5 



15 X 60 



hour candle lights from 1 pound of coal, through the agency of 

 the steam engine and the magneto-electric machine. 



With the thermo-electric battery I have been able to develop 

 180,000 foot-pounds of electricity from 1 pound of coal = 



130,000 



- 144. 4 = to about 144 caudle lights. 

 15X60 



There is still another point of view worthy our attention. Com- 

 mon gas coal will yield about 10,000 cubic feet of gas per 

 ton. This, at 3 hour candle lights per cubic foot, would give 

 (:j X 10,000) -4-2,000=15 hour candle lights per pound of coal. 

 About 25 cubic feet of illuminating gas weigh 1 pound. 

 Hence 1 pound of gas, after it is made from the coal, will yield 

 a light equal to that of a candle for 75 hours. One pound 

 of pure carbon, wholly burned to carbonic acid gas. yields 

 14,500 units of heat, equal to 772 X 14,500= 11,200,000, or 11 1-5 

 millions of f oot-pounds of work ; hence, were the total energy of 

 1 pound of ,ure carbon converted into light, it would be equiv- 

 alent to 1 caudle light for the time of 



11,200,000 



- 1 5-12 =. 1 vear and 5 months. 

 15 X 365 X 24 X 60 



To recapitulate : the gas made from a pound of coal would 

 yield a candle light for 15 hours; 1 pound of the gas would 

 yield a light equal to 1 candle for 75 hours; but could all the 

 energy in u pound of carbon be converted into light, it would be 

 equivalent to the burning of a candle for 12.410 hours. 



Thus it will appear that by our ordinary methods of gas-lighting 

 we utilize :;. uch less than 1 per cent, of the energy stored in the 

 coal. I t'ilnk we may reasonably expect that electricity, as de- 

 veloped by the thermo-electric battery, the magneto-electric ma- 

 chine, or some still more efficient apparatus, will help us in some 

 way to bridge the chasm between 15 and 12.000 hour candle lights 

 from a pound of coal. MOSES G. FARMER, in Scientific Amer- 

 ican. 



IMPROVED MAGNETO-ELECTRIC MACHINE. 



Mr. Tisley, of England, has made a great improvement in the 

 magneto-electric machine, on the suggestion that if the arma- 

 ture had two wires instead of one, the current of one being sent 

 through a wire surrounding the magnets, their power would be 



