THE LENGTH OF DAYS
After the method of M. Carlier, Ingénieur des Arts et Manufactures.
Figured for the latitude of Paris, but applicable so far as the automobilist is concerned to most of continental Europe.
The deeply shaded portions represent night.
The lightly shaded portions twilight.
The white portions daylight.
Generally speaking, lamps must be lighted at the hour indicated by deeply shaded portions in the respective months.