An electrical measuring device, likely a slide-wire Wheatstone bridge. This example is comprised of a richly patinated oak board with a slide wire ruler at the bottom below, and surmounted by eight black Bakelite terminal nut knobs and two switches connected by wires.
A Wheatstone bridge is designed to measure resistance in a conductor by comparing a wire with known resistance to one with unknown resistance. It is used to study the variation of resistance of a conductor with length, diameter and material.
Leeds & Northrup was founded in Philadelphia by Morris E. Leeds as Morris E. Leeds & Company. Dr. Edwin F. Northrup, an educator, scientist and engineer, joined the partnership in 1903. The company produced high quality electrical measuring laboratory instruments. Until then, the best precision instruments came from Germany, but Leeds & Northrop provided an American-made alternative. The company produced a number of innovative measuring devices for education, science and industry, including the world’s first electronic recorder in 1929. Since 1978, the company has been resold and renamed. Since 1995, it has been part of the multi-national Heraeus Electro-Nite Co. and is now known as L&N Metallurgical Products Co., producing industrial molten metal sensors and instrumentation for the international market.
Maker’s metal label: Leeds & Northrup Co./ Scientific Instruments/ Philadelphia/ Ser. No. 216500/ Made in U.S.A.
Condition: Generally very good, the oak nicely patinated, the device with the usual wear and oxidation. Painted number (E-904) under label, probably original owner’s identification. A “0” is later added at the end of each number on the ruler in ink. Tentatively identified by us as a Wheatstone bridge, though this is not our area of expertise. Sold only as a vintage decorative artifact and curiosity, not for use with electricity or other power source.
“L&N Metallurgical Products Co.” Heraeus Electro-Nite. http://www.l-n-metprod.com/interior_h2.html (3 September 2008).“Slide Wire Wheatstone Bridge.” Electrochemical and Electronic Instruments: Institute of Chemistry, The HebrewUniversity of Jerusalem. http://chem.ch.huji.ac.il/instruments/test/bridge_slide_wheatstone.html (3 September 2008).