CH. I] TROUBLES WITH THE MAGIC LANTERN 47 



loosened, or a wire may have become wholly separated from its 

 connections. 



63. A fuse may have burned out somewhere along the line. 

 Commencing with the fuse nearest the lamp, take each fuse out and 

 examine it. Use the testing incandescent lamp also. 



64. A fuse plug may not be screwed in tightly enough to make 

 good contact. Occasionally some one puts a piece of paper or wood 

 in the fuse socket, thus preventing metallic contact. Such 

 obstructions should be looked for and removed; then the fuse plug 

 can be made to produce metallic contact. 



65. The switches may not be properly closed, and hence the 

 circuit is not complete. 



66. The carbons may be so short that they cannot be brought 

 in contact, and thus the circuit cannot be completed. Put in new 

 ones. 



67. The range of the lamp movement may be at its limit, so 

 that the carbons cannot be approximated. This must be corrected 

 by turning the screws back and then setting the carbons by hand, 

 if long enough, or by putting in new carbons. 



68. If one uses an automatic arc lamp, it may be that the 

 mechanism does not work. Before looking elsewhere for the 

 trouble, one should try the hand-feed device present in all auto- 

 matic lamps and make sure that the carbons are brought in con- 

 tact and then slightly separated to establish the arc. 



69. Of course, if one uses a hand-feed lamp it will not start 

 until one brings the carbons in contact by the proper device for the 

 purpose. As soon as the carbons touch there will be a flash of 

 light; then the carbons should be slightly separated. 



70. There may be a short circuit in the lamp itself due to a 

 burning out of the insulation. This may be detected by opening 

 the double-pole knife switch slowly. If there is a big spark when 

 the switch finally opens, a short circuit in the lamp is strongly 

 indicated. 



