Fechner's double sound pendulum for testing aural discrimination
1898-1908
1898-1908
c.1963
1871-1900
1920-1939
1892
1850-1900
1876
1871-1900
1871-1900
1901-1910
1900
1923
1900-1920
1929
1831-1870
1875-1900
1875-1900
1870-1930
1801-1900
1913
1870
1889
1909
1875-1900
1850-1930
1926
1900-1980
circa 1892