Counter for Magnetic Coils
date: label: date made
content: ca 1880
notes: label: Description
content: As the eminent British physicist James Clerk Maxwell pointed out in his <I>Treatise on Electricity and Magnetism</I>, 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.
label: Description
content: 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.
label: Description
content: References:
label: Description
content: Accession File 218174.
label: Description
content: James Clerk Maxwell, <I>A Treatise on Electricity and Magnetism</I>, 2, Oxford: Clarendon Press, 1873, p. 314. Subsequent editions of the book contained the same image.
label: Location
content: Currently not on view
topic: label: Subject
content: Mathematics
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Counters
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content: Science & Mathematics
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.315174
label: catalog number
content: 315174
label: accession number
content: 219145
objectType: label: Object Name
content: counter, analog
label: Object Name
content: counter
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: steel (overall material)
label: Measurements
content: 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