152 



GENERAL SCIENCE 



company. Compute the cost of the gas consumed per hour by the 

 gas appliance. 



NUMERALS REFER TO COST PER HOUR IN MILLS (TENTHS OF A CENT). 



Maximum =10 



Regular Upright Mantle 



Junior Upright Mantle 



(Fish Tail) Burner Turned Down 

 Mantle Pilot 



' Cost of gas used per hour in some common gas appliances 



FIG. 117. What kind of gas light is most economical? What type of burner 

 is very expensive? Why is it cheaper to buy mantles for gas lighting? 

 The cost per hour is calculated on the basis of gas at $1 per 1000 cubic 

 feet. The great difference between maximum and minimum costs is due 

 to difference in size of burners and difference in the pressure of the gas 

 supply. The mean value represents the cost under average conditions. 



For a water heater of ordinary household size the gas would 

 cost from 3 to 8 cents per hour. For larger automatic water heaters 

 gas would cost from 10 to 25 cents per hour for the period that the 



