CH. IV] TROUBLES WITH THE LIME LIGHT 115 



(4) A lime may have broken so that there is nothing for the 

 hot flame to make incandescent. 



Remedy. Turn off the gases the first thing; oxygen first then 

 the hydrogen or other gas. One can then investigate each of the 

 possible causes for the going out of the lamp. The broken lime 

 and the split or separated rubber tube can be most easily detected 

 and corrected, and consequently should be looked for first. 



182. Irregular light or shadows on the screen. The fault 



may lie in any of the following, to name which is to suggest a 

 remedy : 



(1) The lime may be too deeply pitted where the flame strikes 

 it. Change the position of the lime ( 164). 



(2) The lime may be in bad position, too high or too low, too 

 far from or too close to the burner tip. 



(3) The incandescent spot may not be centered on the axis, i. e., 

 be too high or too low; too far to the right or to the left with the 

 resulting shadows as with the crater of the arc lamp (fig. 27-30). 



(4) The light may be too close to or too far from the condenser. 



(5) The nozzle of the burner may be in the way and cast a 

 shadow. If so, it must be lowered or the distance from the lime 

 or the angle changed (see also 82-91). 



183. Roaring or hissing of the burner. A slight hissing sound 

 is usually heard when the right amount of oxygen is being used. 

 But when the roaring becomes annoying its cause must be found 

 and remedied. It may be due to: (i) The inside of the nozzle 

 tube may be rough. 



(2) The lime may not be the right distance from the tip of the 

 nozzle. 



(3) The pitting of the lime may be too great. 



(4) There may be too great a supply of the gases for the bore 

 of the nozzle. 



184. Cracking of the lime. This is usually due to a sudden 

 heating of the lime. If it is warmed gradually by rotating it at 

 first at some distance and then closer to the flame the breaking is 

 usually avoided. If broken, the lime should be removed from the 



