GASEOUS FUKi> 



101 



of air in the carbureter, after which the mixture is drawn into 

 the cylinder, compressed to increase the rate of combustion, 

 and finally burned within the cylinder (see Gas Engines, 

 Chap. X). 



VI. GASEOUS FUELS 



114. Gaseous Fuels. These have long been a favorite 

 kind of fuel. Their use in the home and in various industries 

 has gradually increased. Gaseous fuels are commonly trans- 

 mitted from producer to consumer in pipes. The cost of 

 pipes makes it unprofitable to transmit the fuel long distances. 

 Some gases, as acetylene, are transmitted under pressure in 

 metal tanks (Art. 62). The material for making acetylene, 

 calcium carbide, may be transmitted long distances profitably. 



FIG. 80. An illuminating coal gas plant. 



115. Coal Gas. COAL GAS was the first manufactured gas. 

 It was used for lighting the streets of London and Paris 

 more than 100 years ago. In 1817, the city of Balti- 

 more began to use it for street lighting. The gas is made by 

 distilling soft coal in air-tight retorts (Fig. 80). The coal 

 contains many hydrocarbons which leave it when the coal is 



