Dolezalek quadrant electrometer
1913
1913
1876
1890
1895
1801-1825
1902
1895
1946
1924
1857
1886
1900
1890
1929
1886
1867
1912
1900
1891
1924
1891
1857
1861
1780
1780
1945-1954
1902
1960-1979