Link to Home: Lighting A Revolution  


Curator's Choice for Spring 2000:
Edison Demonstration Lamp, late 1879

Photo of 1879 Edison lamp.

Edison used this lamp (and about 100 more just like it) to illuminate Menlo Park on 31 December 1879 when he introduced his invention to the world. It is currently on display in the exhibition Lighting A Revolution at the National Museum of American History.

SI catalog #310,578; negative #13369.


This lamp and a wooden socket (along with several other pieces relating to Edison) were donated to the Smithsonian in 1933 by Frank A. Wardlaw, Jr. of Inspiration, Arizona, and his father Frank A. Wardlaw of New York, New York. The elder Wardlaw had worked for Edison and at the time of the donation was secretary of the Edison Pioneers.

Photo showing components of 1879 Edison lamp. The lamp may look a bit strange -- it shows many features of experimental Edison lamps, features that have long since been modified or replaced. The "base" consists of two copper plates folded against the neck of the bulb and held in place by a string. Edison designed the first of several screw-bases in mid 1880 so that his lamps could be installed upside-down in fixtures.

The filament (broken in this lamp) is a piece of carbonized Bristol-board - a type of paper -  connected to the lead-in wires with tiny screw-clamps made of platinum. The lead-in wires are also platinum. Though expensive, platinum expanded at nearly the same rate as the glass through which it passed, keeping an air-tight seal as the lamp operated.

Any oxygen inside the bulb would cause carbon filaments like Bristol-board to burn, hence the need for an air-tight seal and also the reason for the glass tip on top of the bulb. After assembly the bulb was connected to a vacuum pump with a thin glass tube. After the air was exhausted from the bulb, a torch was used to melt the tube - sealing the lamp and leaving a tip.

This particular bulb was free-blown, but production demands quickly led to the use of iron molds which allowed fast, uniform results without the need for a master glass-blower. Later, machines were developed which could make thousands of bulbs every hour. The globe on this lamp is dark due to a layer of carbon that evaporated from the filament and settled on the inside bulb-wall.

    For more information see:
  • Robert Friedel and Paul Israel with Bernard S. Finn, Edison's Electric Light: Biography of an Invention (New Brunswick, NJ: Rutgers Univ. Press, 1986).
  • Francis Jehl, Menlo Park Reminiscences (Dearborn, MI: Edison Institute, 1936, 1938, 1941). Three volumes.

To Curator's Current Choice:
To 19th
Century Hall
To 20th
Century Hall
Guest Lounge