NATURAL GAS 389 



is consumed in contact with a mantle of alkaline earth (Ihoria, 

 etc.), the result is the cheapest and best illuminant known. 

 When the price of natural gas is 25 cents per 1,000 cubic feet, 

 and 50 candlepower is obtained from a consumption of 2^ 

 cubic feet per hour, the cost per candlepower per hour is only 

 0.00125 of a cent. 



There were 510,000 domestic consumers of natural gas 

 during 1902, and it is estimated that in the w^estern portions 

 of New York and Pennsylvania, in central and western West 

 \'irginia, and in Ohio, Indiana, and Kansas, not less than 4,500,- 

 000 persons received the benefit of natural gas used as a fuel 

 and an illuminant. Over 8,000 manufacturing establishments 

 were also supplied. 



The introduction of natural gas into the household, for 

 which it is eminently fitted, has been accomplished without 

 personal inconvenience or loss of life, except in very rare cases. 

 The risk from fire is less than when wood and coal are used. 

 There have been some cases of asphyxiation when a stove has 

 been burned in a room without a flue connection, as it has been 

 found by experiment that combustion under these conditions 

 is imperfect, especially so if the air in the room becomes more 

 or less saturated with carbonic acid and the vapors of water, 

 the result being the formation of poisonous carbonic oxide. 



The calorific value of natural gas varies slightly in different 

 localities, as the amounts of carbon and hydrogen vary. Those 

 natural gases w^hich contain the highest percentage of carbon 

 give the best results in evaporating water. The standard used 

 in measuring the evaporation of w^ater is called the British 

 Thermal Unit, and is the amount of heat necessary to raise 

 one pound of pure water 1° F. at or near 39°, which is the 

 temperature of the maximum density of water. The quan- 

 tity of air necessary for the perfect combustion of natural 

 gas varies from 10.4 to 10.8 parts of air to one part of nat- 

 ural gas. The products of combustion are water and car- 

 bonic acid. 



The ultimate heat units in any fuel are not all available 

 for the conversion of water into steam, a proportion being lost 

 by radiation and in causing sufficient draft to supply the fresh 

 air that is required to keep up the combustion. A number of 



