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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



connected in shunt with the armature. It generated electricity at about 

 a hundred volts constant pressure and could supply current up to about 

 60 amperes at this pressure. It therefore had a capacity, in the 

 present terminology, of about 6 kilowatts (or 8 horsepower). 



A multiple system of distribution would make each lamp indepen- 

 dent of every other and with a dynamo made for such a system, the 

 next thing was to design a lamp for it. Having a pressure of about 



Edison Dynamo, 1879. 



Edison made a dynamo that was 90 per cent efficient which scientists 

 said was impossible. This dynamo is in the collection of the Smith- 

 sonian Institution and was one of the machines on the steamship 

 Columbia, the first commercial installation of the Edison lamp. 



a hundred volts to contend with, the lamp, in order to take a small 

 amount of current, must, to comply with Ohm's law, have a high 

 resistance. He therefore wound many feet of fine platinum wire on 

 a spool of pipe clay and made his first high resistance lamp. He used 

 his diaphragm thermostat to protect the platinum from melting, and, 

 as now seems obvious but was not to all so-called electricians at that 

 time, the thermostat was arranged to open circuit instead of short 

 circuit the burner when it became too hot. This lamp apparently 

 solved the problem, and, in order to protect the platinum from the 



