Electromagnetic lever apparatus
date: label: date made
content: ca 1865
name: label: user
content: Henry, Joseph
label: maker
content: Hall, Thomas
notes: label: Description (Brief)
content: Hearder's Magnetometer, an electro-magnet steel-yard and weight on wooden base used as an experimental electromagnetic lever apparatus. A 13 inch lever arm is pivoted at one end near an electromagnet. A 1 kilogram weight can slide along the arm to different positions. The electromagnet shows a dual-coil construction wherein each leg of a U-shaped magnet is wrapped with an inner coil of heavy wire overlaid with an outer coil of fine wire. There are four connector posts, two stamped "C" and connected to the heavy inner coils, and two stamped "F" and connected to the fine outer coils. It is not clear if the coils are interconnected but they appear to be separate.
label: Description (Brief)
content: Jonathan Nash Hearder (1809-1876) was an electrician in Plymouth, England, who, in the early 1840s, developed a magnetometer for ascertaining the rate of magnetic development in iron. Instruments of this sort would later be used to test the strength of magnets, largely for telegraphic purposes. This example was used by Joseph Henry, the physicist who served as founding Secretary of the Smithsonian Institution. The “T. Hall” inscription on this example refers to Thomas Hall (1826-1919), an immigrant from England who apprenticed with Daniel Davis in Boston, and took over the instrument business following Davis’ retirement in around 1850.
label: Description (Brief)
content: "Mr. Hearder, of Plymouth, had some very beautiful electro-magnetic apparatus of great power, which he frequently described to his visitors in his lucid and interesting manner." One was a powerful rotary electro-magnetic engine. Another was the "Magnetometer for ascertaining the conditions which modify magnetic development in iron, surrounded by a coil of wire conducting electricity." (This is the steelyard device, as we have). Also a cast iron magnet, and a vibrating magnetic engine. Reference: “Royal Cornwall Polytechnic Society,” <i>Cornwall Royal Gazette</i> (Aug. 30, 1844).
label: Description (Brief)
content: Additional references:
label: Description (Brief)
content: J. N. Hearder, “Description of the Apparatus Shown at the London Institution,” <i>The Electrical Magazine</i> 2 (1845): 133-137.
label: Description (Brief)
content: Henry Noad, <i>A Manual of Electricity</i> (London, 1859), volume 2, 684-686.
label: Description (Brief)
content: Taliaferro Preston Shaffner, <i>The Telegraph Manual</i> (New York, 1859), 126-128.
label: Description (Brief)
content: Daniel Davis, <i>Manual of Magnetism</i> (Boston: published by Thomas Hall, 1865), 191-195; here the device is termed an axial magnetometer.
label: Description (Brief)
content: <i>Exhibits of the Smithsonian Institution and the United States National Museum at the Alaska-Yukon-Pacific Exposition, Seattle, Washington, 1909</i> (Washington, 1909), 21.
label: Location
content: Currently not on view
setName: label: See more items in
content: Work and Industry: Electricity
creditLine: label: Credit Line
content: from the Smithsonian Institution Collection of Apparatus, thru William C. Winlock
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: EM.181448
label: catalog number
content: 181448
label: accession number
content: 2006.0177
objectType: label: Object Name
content: magnetometer
label: Other Terms
content: Balance, Electric; magnetometer; Magnetic Devices; Electromagnetic Devices; Electromagnetic Devices
physicalDescription: label: Measurements
content: overall: 5 in x 18 1/4 in x 6 in; 12.7 cm x 46.355 cm x 15.24 cm