Counter for Magnetic Coils

Description
As the eminent British physicist James Clerk Maxwell pointed out in his Treatise on Electricity and Magnetism, it was important for 19th century scientists to count the number of turns of wire laid down in constructing galvanometer coils and similar electrical instruments. To do this, Maxwell used a string attached to a shaft turned by the same lathe that held the wheel on which the wire of the coil was wound. Nails helped count the turns of the shaft marked by the string. A device linked to the wheel measured the wire as it turned on the wheel to form the coil, detecting changes in circumference.
This instrument has a brass wheel 18 cm. in diameter. The wheel turns in a steel yoke with a wooden handle. According to the accession file, it was designed by James Clerk Maxwell for measuring the wire in a coil. It lacks a counting element and has no maker’s marks.
References:
Accession File 218174.
James Clerk Maxwell, A Treatise on Electricity and Magnetism, 2, Oxford: Clarendon Press, 1873, p. 314. Subsequent editions of the book contained the same image.
Location
Currently not on view
Object Name
counter, analog
counter
date made
ca 1880
Physical Description
wood (overall material)
brass (overall material)
steel (overall material)
Measurements
overall: 8 cm x 18.3 cm x 39.4 cm; 3 5/32 in x 7 7/32 in x 15 1/2 in
ID Number
MA*315174
catalog number
315174
accession number
219145
subject
Mathematics
Science & Mathematics
Counters
See more items in
Medicine and Science: Mathematics
Counters
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

Visitor Comments

Add a comment about this object

**Please read before submitting the form**

Have a comment or question about this object to share with the community? Please use the form below. Approved comments will appear on this page and may receive a museum response (but we can't promise). Please note that we generally cannot answer questions about your own artifacts or tell you how much they are worth.

Have a question about anything else, or would you prefer a personal response? Please visit our FAQ or contact page.

Personal information will not be shared or result in unsolicited e-mail. See our privacy policy.

Image CAPTCHA
Enter the characters shown in the image.