rhythm of marks by night
Lights that shine at night; their color and the frequency of their flashing signal various meanings, including the source of the light.
interval 
Duration between two periods at which time the light remains dark.
interval 
Duration between two periods at which time the light remains dark.
period 
Duration between two intervals at which time the light signals.
period 
Duration between two intervals at which time the light signals.
period 
Duration between two intervals at which time the light signals.
light 
The light’s color and brightness vary during the period as a function of the type of light.
darkness 
No light.