420 



OPTICAL PROJECTION 



enough gas to supply a lantern acetylene jet for nearly two hours. 

 There were at first difficulties in consequence of the explosive pro- 

 perties of the gas, but now all modern lantern generators are so 

 constructed that they only produce the gas in very small quantities 

 as required, and under no circumstances should there ever be 

 enough to cause an explosion. 



FIG. 235. Acetylene Generator 



The number of these generators on the market at present ia 

 legion, and it would be useless to attempt to describe them. 



They may practically all be divided into two classes : those in 

 which the carbide drops a little at a time into the water, and those 

 in which the water is gradually admitted to the carbide, which, in 

 this form of generator, is usually placed in small trays or cells. 



