48 



THE PRODUCTION AND USE OF LIGHT 



inverted and floating upon the water within the first. The gas 

 confined within the smaller can supports it. As the gas is 

 used, the smaller can falls. 



60. Automatic Feed Generators. These generators are 

 arranged so as to feed the carbide into the generator tank as 

 fast as the gas is consumed, Figs. 31 and 32. When the gas- 

 holder can has fallen because of the removal of gas from the 



holder, a lever which is attached 

 to the can opens a valve at the 

 bottom of the carbide holder, 

 thus allowing carbide to drop 



FIG. 31. Acetylene generator. 



FIG. 32. Sectional view of acety- 

 lene generator. 



into the water and generate gas. As the gas accumulates in 

 the gas holder the can rises, and the lever closes the valve at 

 the bottom of the carbide holder and the generation of gas stops. 

 61. The Cost of Acetylene. One pound of calcium carbide 

 will produce from 4.25 to 4.85 cu. ft. of acetylene, depending 

 upon the size of the carbide lumps, the larger lumps producing 

 more gas than the smaller ones. In 100-lb. drums the carbide 

 may be purchased for about $4.50, so that the cost of the acety- 

 lene is very nearly 1 ct. per cu. ft. Ordinary illuminating 

 gas sells for about Jfo c ^- per cu. ft. However, a cubic 

 foot of acetylene will produce about twice as much light as 



