
High-sensitivity mirror galvanometer
circa 1920
circa 1920
1924
circa 1890
1940
1916
1895
1930
1910
1914
1940
1905
1920
1920
1938
1930
1888
1924
1925
1955
1959
1925
1897
1936
1910
1924
1933
1930
1943
1911
1932
1935
1941
1928
1960
1930
1930
1910
1946
1928
1904
1955
1910
1920
1890