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