82 THE BOOK OF THE LANTERN. 



pattern of very compact form is illustrated at fig. 34. In 

 this case the by-passes are governed by taps which are 

 adjusted by the operator with a screw-driver. This seems 

 to be a good arrangement, as there is no chance of 

 accidental turning off or on by a careless touch, as may 

 happen when the by-pass taps are exposed. 



FIG. 34. 



There are one or two methods of manufacturing oxygen 

 gas for the limelight as fast as it is used, and although, 

 for reasons which I shall presently give, I cannot recom- 

 mend such a procedure, the methods are ingenious enough 

 to warrant notice. In Chadwick's apparatus there is an 

 iron gas-holder, which forms the support of the lantern. 

 Associated with it is a special form of retort heated by a 

 Bunsen burner, and charged with chlorate of potash and 

 manganese made up into a cake previously. The operator 

 starts with a full gas-holder, and at the end of perhaps 

 fifteen minutes, when it is nearly empty, lights the Bun- 

 sen burner, and in a few minutes enough gas is generated 

 to fill it once more. The retort is now charged with a 

 fresh cake of mixture ready for once more filling the gas- 

 holder as it sinks. 



