Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
after 1903
1895
circa 1900
circa 1900
1903
1902
circa 1880
1900
1884
1901
circa 1885
1895
1896
1906
1902
1898
1901
circa 1905
1886
1906
1896
1904
1901
1885
1898
circa 1890
circa 1890
circa 1890
circa 1890
1898-1899
1902-1907
1903
1892
1934
1906
1903
1889
circa 1900
1898
1899
1901
1904
1897
1887-1903
circa 1897
About 1890
1884
1892-1900
1880-1900