io8 MANAGEMENT OF THE LIME LIGHT [Cn. IV 



but it has a dangerous sound; and the purpose of the exhibition is 

 to instruct or entertain, not to scare the audience. To insure the 

 correct use of the gases it is a good plan to have the stop-cock 

 handles of the two gases so different that one can tell by feeling 

 which one is being turned on. 



FIG. 60. FLEXIBLE METALLIC TUBING WITH RUBBER CONNECTORS AT 



THE ENDS. 



(Cut loaned by the Pennsylvania Metallic Tubing Co.). 



161. Regulating the flame. Theoretically the proportion of 

 the two gases should be their combining quantities (H 2 O) ; but 

 experience has shown that better results are gained when the 

 hydrogen is in excess. When the oxygen is in exactly the combin- 

 ing proportion there is liable to be a snap and the light goes out. 

 If there is an excess of hydrogen this docs not happen. As stated 

 above, the oxygen should be added until the flame just begins to 

 hiss. 



162. Putting a lime in position. A fresh lime from the box 

 should be put in position in the burner (fig. 59 L) before lighting 

 the hydrogen, but the lime should at first be 3 to 5 cm. (i to 2 in.) 

 distant from the tip of the nozzle (fig. 59 N), and it should be 

 rotated, raised and lowered until it is warmed. If the full heat of 

 the O-H flame were directed against one point of the cold lime for 

 too long a time the lime would be liable to break. After it is well 



