
Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
1901-1913
1914-1918
1914-1918
1872 (original); 1909 (model)
1914-1918
circa 1900
1914-1918
1900
1903
1903
1898-1899
1900-1920
1920
1914-1916
1904-1914
1916
1901
1906
1898
1906
1912
1915
1910
1917
1910
1918
1907-1917
1912
1907-1917
1907-1917
1915
1921
1906
1901
1900-1910
1915
1899
1899
1910-1920
1934
1901
1902-1907
1920
1907
1914
after 1903
1900-1920
1898-1900
1914