66 THE BOOK OF THE LANTERN. 



regulated a very difficult matter by the screw plug on 

 the nozzles of the bottles. 3. The operator at the lantern, 

 even if he succeed in thus procuring the delivery of the 

 proper amount of oxygen and hydrogen respectively, must 

 stoop down to do so, and, for the time, neglect other duties. 

 4. The pressure is constant ; and, therefore, if a double or 

 treble light is suddenly wanted as in the case of biunial 

 and triple lanterns the amount of gas measured out for one 

 light, must serve for two or three, as the case may be 

 and all suffer. 5. As the bottles gradually empty, the 

 pressure sinks ; and, therefore, the screw-plugs have to be 

 opened several times during an evening's work. Every 

 time this becomes necessary, there is a likely chance of too 

 much being turned on, and the tubes being blown off. It 

 is, therefore, seen that, although bags are troublesome, 

 bottles possess many disadvantages which would make any 

 careful operator pause before he adopted them. These 

 disadvantages, however, entirely disappear when the 

 bottles are used with regulators. 



The action of the regulator can be understood without 

 much difficulty by reference to the annexed sectional 

 diagram, fig. 28. The screw-thread d* at the bottom of the 

 drawing, is where the casting D fits upou the bottle of 

 compressed gas ; d l is the delivery tube, governed by the 

 stop-cock d 2 . B is a base-plate supporting the most im- 

 portant part of the apparatus, and E E standing upon it 

 is merely a casing to protect the enclosed part from injury. 

 A A are bellows made of the finest rubber, and of a form 

 not unlike the bellows of a camera, only that it is circular. 

 The top of the bellows is heavily weighted, jso that its 



