LIST OF ILLUSTRATIONS. 
Page. 
Model showing how coal is transmuted into gas and delivered to 
home Frontispiece. 
Fig. 1. Growth of manufactured-gas sales for public-utility service in the 
United States 2 
2. Number of manufactured-gas consumers in even thousands to 
each State 3 
3. Fuel small part of total meal cost 5 
4. Relative cost of “ home-cooked ” and “ ready-to-serve ” cereals 6 
5. Relative cost of various fuels for cooking a dinner 6 
6. Comparison of gas used by public and gas wasted in beehive 
coke ovens 8 
7. Classification of manufactured-gas consumers 9 
8. Action of gas mixer for Bunsen blue-flame burner 14 
9. Action of luminous-flame burner 14 
10. How fluctuations in atmospheric temperature varies demand for 
house heating 21 
iv 
