One of the things that attracted me to Paris when I was young, was that our west coast lighthouses built in the 1800s were built with glass that came from Paris, France! The glass was cut and put into a lighthouse so that the oil light that was kept lit 24 hours a day by the Lighthouse Keeper and his assistant could be seen for miles at sea, the glass was Fresnel Glass. The glass was built in Paris and then shipped around The Horn to get to its destination of the West Coast of the United States.
Here is a copy out of Wikipedia that explains the glass: “A Fresnel lens (pronounced // fray-NEL or // FREZ-nel) is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses. The design allows 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 capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances.”
Below are a couple pics taken of the glass and first one shows the optical illusion it creates when standing in a lighthouse looking out through the it and how the world looks upside down and an up close view of the glass showing the stamp of made in Paris!