40 SCIENCE OF HOME AND COMMUNITY 



ment has been made through the use of mantles, which give 

 a stronger light and use less gas. These mantles are made 

 of substances which do not burn, but which when heated 

 give off a bright light. Mantles must be replaced occasion- 

 ally, as they are so fragile that they are very easily broken. 

 In burners that are equipped with mantles a special arrange- 

 ment is made for admitting a large supply of air so that more 

 complete combustion takes place. This gives a higher 

 temperature, which makes the mantles incandescent. 



HOME PROJECT 5 



Purpose. To read the gas meter and learn the cost of the gas 

 used. 



Directions, i. If you use gas in your home, make a read- 

 ing of the meter. Make a drawing of the circles on the meter 

 and indicate the pointer in each in the proper position. Record 

 the reading of the meter. Notice how the gas can be turned 

 off in case it should be necessary, as when gas escapes from a 

 broken pipe. One week later, read the meter again and make 

 another drawing. Subtract the first reading from the second 

 to find how much gas was used in a week. Find the price of 

 gas and compute the cost of the gas used in one week. 



2. In order to find out whether the gas pipes leak, read the 

 small dial called the test dial, just after the gas is turned off for 

 the night. Read the dial again the next day just before the 

 first burner is lighted. Any difference in the readings represents 

 the amount of gas that has leaked from the pipes. 



Acetylene. The chief advantage in the use of acetylene 

 gas lies in the fact that it can be installed for isolated houses 

 too far away from towns to use gas or electricity. The gas 

 is made by adding water to a solid substance called calcium 

 carbide. The generating apparatus is so arranged that -the 

 water and carbide are brought in contact, the gas is collected 

 in tanks, and the amount of gas generated is regulated by 

 pressure. The house is piped as for gas, and the pipes are 



