ILLUMINATING GAS LIGHTING 



45 



55. Reading a Gas Meter. The small upper dial on a gas 

 meter is the TEST DIAL. It is generally used only in testing the 

 accuracy of a meter. The other dials are the ones ordinarily 

 used in reading the amount of gas consumed. 



Exercise 20. To Study the Recording Mechanism of the Gas Meter 



Notice that the right-hand pointer revolves in a clockwise direction, 

 that the second pointer revolves in a counter-clockwise direction and 

 the third revolves in a clockwise direction. Study the gear wheels 

 to see why this is so. Notice that a small cog wheel on the shaft 

 which carries the TEST POINTER engages a large cog wheel on the shaft 

 which carries the right-hand pointer. By counting the cogs on each 

 of the wheels determine how many turns the test pointer makes to 

 one turn of the right-hand pointer. 



CUBIC 



FEET 



FIG. 26. This meter reads 47,750 cubic feet. 



The right-hand pointer makes one complete revolution while 1000 

 cu. ft. of gas is passing through the meter; the second pointer makes 

 one revolution while 10,000 cu. ft. of gas is passing through the meter. 

 See that the number of cogs in the gear wheels indicates this relation 

 (Fig. 26). 



What is the reading of the gas meter you have been studying? 



Read the gas meter at the school, or at home, every day for a week, 

 keeping a careful record of the readings in your permanent notebook. 

 You will need these readings later. 



56. Determining the Pressure of Gas. 



Exercise 21. To Measure the Pressure of Gas 



Connect a U-tube with the gas jet as shown in Fig. 27. Fill the 

 U-tube half full of water. Support the apparatus in an upright posi- 

 tion. Such a piece of apparatus is called a MANOMETER. Carefully 



