Lighthouses of the world

A.L.🗼🗼Donaghadee Lighthouse is a lighthouse in Donaghadee County Down, Northern Ireland. Donaghadee is probably best known for its lighthouse and harbour. There has been a haven for ships at Donaghadee (locally known colloquially as the 'Dee') for centuries, and there has also existed a harbour since at least the 17th century.
Constructed 1836

Pigeon Point Lighthouse, West Coast, California, USA.

Point Abino Lighthouse , Lake Erie

Florence Oregon, Lighthouse! Heceta Head Lighthouse is a working 19th-century lighthouse is now home to a B&B with 6 rooms offering scenic views.

We were able to walk the beach next to  this lighthouse some years ago. 

Beautiful Cana Island Lighthouse.

I was able to climb this Door County, Wisconsin lighthouse a few years ago. 

Esopus Meadows Lighthouse during sunset in Port Ewen, New York, USA.

The Chicago Harbor Lighthouse was built in 1893 for the World's Columbian Exposition. It resides near the mouth of Chicago River in Illinois, US 🇺🇸

Eagle Harbor Lighthouse in Michigan.

The Fresnel Lens:

The heart of a lighthouse!

In the 1700 and 1800’s open water shipping was the lifeline of commerce – it was the only way to transport goods between the continents, but it wasn’t easy. Among the many difficulties was the problem of ships, and all of their precious cargo running aground and being smashed on unseen rocks.

This necessity brought about the creation and design of many lighthouses on the coastlines, which would let ocean navigators see when they were getting too close to dangerous outcrops. The issue was, the lights were essentially a large candle or oil lamp, and many times they were so dim that when the boat Captain saw the light, it was already too late. So scientists of the day searched for ways to focus and project the light much further.

French physicist and engineer Augustin-Jean Fresnel developed the multi-part Fresnel lens for use in lighthouses. His design allowed for the construction of lenses of large aperture and short focal length, without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can also capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one, to be visible over greater distances.

Sambro Island Lighthouse

Nova Scotia, Canada 
Photo by @Archer10