6o SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 76 



Electric street railway systems used a voltage in the neighborhood 

 of 550, and lamps were designed to burn five in series on this voltage. 

 These lamps were different from the standard i lo-volt lamps although 

 they were made for about this voltage. As they were burned in series, 

 the lamps were selected to operate at a definite current instead of at 

 a definite voltage, so that the lamps when burned in series would 

 operate at the proper temperature to give proper life results. Such 

 lamps would therefore vary considerably in individual volts, and 

 hence would not give good service if burned on iio-volt circuits. 

 The candelabra screw base and socket and the miniature screw base 

 and socket were later developed. Ornamental candelabra base lamps 



Thomson-Houston. Westinghouse. 



Adapters for Edison Screw Sockets, 1892. 



Next to the Edison base, the Thomson-Houston and Westinghouse 

 bases were the most popular. By use of these adapters, Edison base 

 lamps could be used in T-H and Westinghouse sockets. 



were made for use direct on no volts, smaller sizes being operated 

 in series on this voltage. The former gave about lo cp, the latter in 

 various sizes from 4 to 8 cp. The miniature screw base lamps were 

 for low volt lighting. 



The various manufacturers of lamps in nearly every instance made 

 bases that were very different from one another. No less than four- 

 teen different standard bases and sockets came into commercial use. 

 These were known as, Brush-Swan, Edison, Edi-Swan (double con- 

 tact), Edi-Swan (single contact). Fort Wayne Jenny, Hawkeye, 

 Indianapolis Jenny, Loomis, Mather or Perkins, Schaeffer or Na- 

 tional, Siemens & Halske, Thomson-Houston, United States and 

 Westinghouse. In addition there were later larger sized bases made 



