Hilger wavelength spectroscope, with camera, London, England, 1919
1919
1919
1871-1900
1875-1885
1875
1956
1967-1973
1850-1924
1850-1924
1875-1885
1874
circa 1870
1920
1871-1900
1960-1969
1880
1908-1928
1900-1980
1863
1919
1919
1885-1895
1900
1865-1875
1984
1874
1865-1875
1984
1874-1904
1850-1924
1900