Historic oil on canvas, contemporary inserts, lacquered wood.
Time worked for an hour of light.
1800 - 6 hours work for an hour of light 1850 - 2.5 hours work for an hour of light 1900 - 11 minutes work for an hour of light 1950 - 8 seconds work for an hour of light 2000 - 2 seconds work for an hour of light