96 TROUBLES WITH SMALL CURRENT LANTERNS [Cn. Ill 



147. Troubles with the magic lantern on the house lighting 

 system. With the arc lamp these are the same as those indicated 

 in Ch. I, 62-98; Ch. II, 116-118. See also i28a for fuses. 

 There is also the danger of starting an arc in the incandescent 

 socket from which the current is drawn unless the precautions given 

 in 133 for turning out the light are observed. 



For all the lights the management of the exhibition, centering of 

 apparatus, etc., are the same as for the lanterns in Ch. I, II. 



The most striking difficulty will probably be the comparatively 

 dim screen pictures as compared with the brilliant screen images 

 given by the large current arc lamp. 



The room must be darker and the screen picture smaller with 

 these lights. 



The Mazda lamp may go out on account of the breakage of some 

 of the connections within the bulb. If this happens the only thing 

 to do is to use a new lamp. It is wise to have several on hand. 



With the Nernst lamp also some of the connections are liable to 

 break, or the ballast may burn out, or the glower be broken. 

 Usually only the defective parts must be renewed, and not an 

 entirely new lamp obtained. 



