Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
1898
1902-1907
1898
1934
1899
1906
1955; 1830
1898
circa 1897
after 1903
1908
1901
circa 1900
1900
1899
1905
circa 1900
1903
1902
1900
1901
1906
1902
1898
1901
circa 1905
1906
circa 1900
1898
1899
1901
1901
2000-100 BCE
1898-1899
1899
1899
1903
1904
1901
1900
1904
1899-1901
1903
1902
1904
1872 (original); 1909 (model)
1897
1898-1900
1901