Old Third-order Fresnel lens from the New Point Loma Lighthouse.
It was installed in 1891 and cost $4,000 at that time.
At its peak it has 120,000 candle power and could be seen at a distance in excess of 30 miles.
The incandescent oil-vapor light used one gallon of oil per night.
It is basically a twelve sided rotating box of glass with walls made of prisms designed to shine light as far possible.




The image above was taken for the Weekly Informal Challenge (Week 88): "Complex"

You can read the rules and check out images of other participants here