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