Henley needle galvanometer, 1855-1860
1855-1860
1855-1860
1858
1865-1866
1843-1897
1858
1830-1870
1854
1858
1864-1886
1881-1926
1890-1930
1920-1930
1943-1970
1900
1910
1955
1959-1961
1910-1920
circa 1902-1925
1890-1891
1890
1926
1878-1900
1852-1870
1880-1920
1858
1963
1898-1913
1926
1906
1935
1900
1920-1955
1920
1850-1924
1888
1921
1901-1908
1859
1908
1960
circa 1910