ELECTRIC LIGHTING 



51 



The over-heating of electric wires sometimes causes fires. 

 If the wires in a building should be too small to carry the 

 current which is sent over them, they may become very hot 



FIG. 35. Electric current 

 heating a wire. 



FIG. 36. Incandescent 

 lamp and socket. 



and set on fire the wood or other burnable material with which 

 they come in contact. For this reason all cities have very 

 strict rules and ordinances governing the wiring of buildings 

 for electric lighting. 



65. The Incandescent Lamp. 

 The incandescent lamp is very 

 simple in principle. It consists 

 of a glass bulb from which practi- 

 cally all of the air has been re- 

 moved. Sealed into the base of 

 the globe are two pieces of plati- 

 num wire. The base, or top, of 

 the bulb is set by means of plaster 

 of Paris in a brass base which can 

 be screwed into a SOCKET (Fig. 



36). One of the platinum wires is soldered to the brass base 

 at A, the other is soldered to the plate at the center of the 

 base at B. When the lamp is screwed into the socket, B 



FIG. 37. 

 bon lamp. 



FIG. 38. Tung- 

 sten lamp. 



