Description: Spring balance electrometer.

Caption: This instrument weighed a static electric charge or 'potential' now known as 'voltage'. However, it suffered from small errors caused by frictional forces in the mechanism, non uniformity of the electric charge on the plates and moisture in the glass leyden jar. It is unsigned, but was probably made by James White of Glasgow, in 1855.

Introduction: Kelvin's greatest achievement in the field of static electricity was the development of a series of electrometers, beginning with this instrument in 1855. They were used in the laboratory as standards for calibrating other instruments. They were also used for measuring potentials of both static and direct current electricity.

Background: Static electricity, which for all intents and purposes discharges instantaneously, had been known since ancient Greek times, as the mysterious force produced from rubbing amber with a cloth. the word electricity is itself derived from the Greek word for amber - 'elektron'.

Reference: Green, George & Lloyd, John T.. "Kelvin's Instruments and the Kelvin Museum", 1970 p. 59

Reference: Holbrook, Mary. "Science Preserved A Directory of Scientific Instruments in the collections in the United Kingdom and Eire", 1992 p. 132

Reference: Thomson, William. "Mathematical and Physical Papers", Vol I Art. LXII 1882

Historical Context: Design of the Coulomb balance - When: 1874 - Where: France - Who: Coulomb, Charles Augustin de (1736-1806) French physicist

Historical Context: Design of this form of the attracted disc electrometer - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Design of this form of the attracted disc electrometer by Lord Kelvin - When: 1853-1855 - Where: Glasgow, Scotland

Historical Context: Invention of the attracted disc electrometer - Who: Harris, William Snow, Sir (1791-1867) Physician, gentleman scientist and electrician

Historical Context: Invention of the attracted disc electrometer by Harris - When: 1834 - Where: England

Historical Context: Manufacture - When: 1855 - Where: Glasgow, Scotland - Who: James White & Company

Historical Context: Publication of the invention of Gilbert's "versorium" in "De Magnete" - When: 1600 - Where: London, England

Historical Context: Publication of the ivention of the electroscope Gilbert called a "versorium" in "De Magnete" - Who: William Gilbert (1540-1603) English physician

Historical Context: Used at the Gilbert Scott Buildings in lecture demonstrations in the Department of Natural Philosophy - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Used in the Department of Natural Philosophy now called the Department of Physics and Astronomy - Where: Natural Philosophy Lecture Theatre, Gilbert Scott Building, University of Glasgow, University Avenue, Glasgow, Scotland - Where: Natural Philosophy Lecture Theatre, Gilbert Scott Building, University of Glasgow "Old College", High Street, Glasgow, Scotland

Historical Context: Used in the Gilbert Scott B'lding by Prof. William Thomson in the Department of Natural Philosophy now called the Department of Physics and Astronomy - When: 1870-1899 - Who: Thomson, William, Professor (1824-1907) Sir William Thomson from 1866 and Ist Baron Kelvin of Largs from 1892 better known as Lord Kelvin

Historical Context: Used in the Old College by Prof. William Thomson in the Department of Natural Philosophy now called the Department of Physics and Astronomy - When: circa 1855-1870

Historical Context: Event - "Lord Kelvin: A life in science" exhibition, Hunterian Museum, University of Glasgow. Object on display in this exhibition.