108 CALORIFIC POWER OF FUELS. 



position occurs, and a gas of high candle-power is formed. 

 This is collected, and after compression supplied to the con- 

 sumers. It loses some 20 per cent of the illuminating power 

 during compression. As a source of heat, its use is, so far, 

 very limited. An analysis and heat test will be found in the 

 tables. 



The Archer gas process is somewhat similar to the Pintsch, 

 but the products of decomposition are generated at a com- 

 paratively low temperature, and then superheated subse- 

 quently so as to make the gas permanent. This gas is used 

 for metallurgical purposes, but its use for heating boilers is 

 very limited. 



The other gases made with steam or steam and air have 

 been advertised or pushed as fuel gases for several years. 

 Many plants have been established and failed. A few of the 

 most prominent are mentioned in the tables. 



OTHER GASES. 



Gas has been obtained from destructive distillation of 

 wood, rosin, fats, and other materials. They were used prin- 

 cipally for illumination, and seldom if ever for heat. They 

 are now made only in very exceptional cases. 



