ACETYLENE FOR LIGHTING 



227 



Cubic 



what direction each of the hands of Fig. 212 must have 

 moved to come to its present position; then write down 

 the meter "reading" shown in the figure. 



The gas meter consists of two compartments the size of which is 

 controlled by two movable diaphragms, or disks. The diaphragms are 

 forced inward and outward by the 

 pressure of the gas from the city 

 ' ' mains." A ' ' slide valve " (cf. 24, 

 Fig. 19) changes the course which 

 the gas must take, so that the 

 compartments may be first filled, 

 and then emptied. As the dia- 

 phragms move back and forth, 

 they give their motion to the re- 

 cording hand of the dial. Since 

 the capacity of the compartments 

 is known, and the dial shows how 

 many times the compartments have been filled and emptied, the dial 

 also shows how many cubic feet of gas have passed through the 

 meter. 



Fig. 212. 



Gas Meter. The dials read up to 5, 1 ,000, 



10,000, and 100,000 cubic feet, 



respectively. 



257. Acetylene for Lighting. Acetylene (cf. 120 

 and 158) is made by the action of water upon calcium 

 carbide. It contains a large proportion of carbon, and 

 burns with a very smoky flame. Hence the acetylene 

 burner must be different from an ordinary 

 gas burner. The most common form is 

 shown in Fig. 213. In this burner the 

 acetylene is mixed thoroughly with air, 

 and the two jets of burning gas are made 

 to strike each other. The result is an out- 

 Fig. 213. spread, "fish-tail" flame. It is smokeless, 

 ABu ie n n e e r G r as Acety - and of brilliant whiteness. 



