flat spiral (or ribbon) coil
Date: 1842-1855
Inventory Number: 0101
Classification: Induction Coil
Dimensions:6 × 25.2 × 22.5 cm (2 3/8 × 9 15/16 × 8 7/8 in.)
Bibliography:A Manual of Magnetism
Davis's Manual of Magnetism
Davis's Manual of Magnetism
Daniel Davis, Jr. and the Elecromagnetic Instrument Industry: A Field with Great Potential in the Early 19th Century
Catalogue of apparatus to illustrate magnetism, galvanism, electrodynamics, electromagnetism, magneto-electricity, and thermo-electricity, manufactured and sold by Daniel Davis, magnetical instrument maker
DescriptionA one-inch wide strip of copper ribbon is wound into a spiral, making a flat surface, with painted fabric intervening each winding. Two brass binding posts make battery connection with the inner and outer end of the long strip.
This is how Davis described this instrument in his 1842 book on magnetism: "The copper ribbon may be an inch wide and one hundred feet long, the strips being cut from a sheet, and soldered together. Being then wound with strips of thin cotton, it is coiled upon itsef, like the mainspring of a watch; in[s]tead of covering it with cotton, it may be coiled with a strip either of cotton or list intervening. Two binding screw cups are soldered to the ends of the ribbon; the internal end, for convenience, is brought from the centre, underneath the spiral, to its outside, care being taken to insure insulation where it passes the coils. The whole may be firmly cemented together, if desired, by a solution of shellac in alcohol." (pp. 73-74)
The device was sold by Davis $0.75 to $1.00 per pound in 1848.
Signedunsigned
FunctionThe self-induced spark and shock in an electrical circuit is augmented by including a spiraled winding. These spiral coils (see also 0102 and 0103) were used to demonstrate that effect, as well as the induction of third and higher order induced currents, as first demonstrated by Joseph Henry around 1838.
From Davis's description (1842): "The spiral being connected with the battery, its two faces will exhibit strong polarity: a dipping needle placed on any part of its surface or near it will always direct one of its poles towards the centre..." (p.74)
Primary SourcesDaniel Davis, Jr., Davis's Manual of Magnetism (Boston: Daniel Davis, Jr., 1842), 73-75, 145-153.
Daniel Davis, Jr., Catalogue of Apparatus, to Illustrate Magnetism, Galvanism, Electrodynamics, Electro-Magnetism, Magneto-Electricity, and Thermo-Electricity (Boston: Daniel Davis, Jr., 1848), 14, fig. 167.
Daniel Davis, Jr., A Manual of Magnetism, 2nd ed. (Boston: Daniel Davis, Jr., 1848), 172-173, 254-263.
Daniel Davis, Jr., Davis's Manual of Magnetism, 7th ed. (Boston: Palmer and Hall, 1855), 172-173, 254-263.
ProvenanceFrom the Department of Physics, Harvard University.
Related WorksSara Schechner, "Daniel Davis, Jr. and the Electromagnetic Instrument Industry: A Field with Great Potential in the Early 19th Century," unpublished manuscript (1978), available in the CHSI Library (Lib.4884).