Holtz-type influence machine

Holtz-type influence machine

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Description (Brief)
People from ancient times knew that rubbing certain materials and then touching something caused a spark. Studying what is called electrostatics laid the groundwork for understanding electricity and magnetism. Natural philosophers, scientists, and instrument makers created many ingenious devices to generate electrostatic charges starting in the 1600s. These machines varied in size and technique but all involved rotary motion to generate a charge, and a means of transferring the charge to a storage device for use.
Many early electrostatic machines generated a charge by friction. In the later 19th century several designs were introduced based on induction. Electrostatic induction occurs when one charged body (such as a glass disc) causes another body (another disc) that is close but not touching to become charged. The first glass disc is said to influence the second disc so these generators came to be called influence machines.
This machine—with two plates, one fixed and one that rotates--was made by Heinrich Ruhmkorff (1803-1877) of Germany in his Paris workshop. He is best known for the development of an induction coil still known as a Ruhmkorff coil. Designed by Wilhelm Holtz (1836–1913) four glass rods mounted on a mahogany base support two glass discs about 22" (56 cm) in diameter. The operator cranks driving pulleys to spin one plate. An extra set of combs are set at right angles to the ones typically seen in the basic Holtz design. One plate has two holes and paper tabs.
Research indicates this 2-plate machine may have been purchased by Joseph Henry for research use at the Smithsonian. Another Ruhmkorff machine with four plates designed in the 1870s is catalog #328747.
This machine was repaired in late 1958 and the parts replaced included the stationary plate, stationary plate holding-support screw, stationary plate positioning knob and ferrule, and the drive belts for the rotating plate The original glass plates are in storage.
Currently not on view
Object Name
Electrostatic Machine
electrostatic generator
influence machine
Other Terms
electrostatic generator; Electrostatic Devices
date made
ca 1875
ca 1870
associated person
Ruhmkorff, Heinrich Daniel
overall: 27 1/4 in x 27 1/2 in x 17 in; 69.215 cm x 69.85 cm x 43.18 cm
ID Number
catalog number
accession number
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Work and Industry: Electricity
Science & Mathematics
Data Source
National Museum of American History
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