One, and only one, of the interesting things to see in the Calhoun County Museum is the Lighthouse lens that was in the Matagorda Island light house. It is a huge thing and is full of rings and ridges. That type of lens is called a Fresnel Lens and was and still is popular in light houses after 1822 or so when a French engineer, Auguste Fresnel invented it. They were popular because the beam will be visible twenty or so miles out from the light.
Like all really popular inventions there is a little controversy about who did the actual invention. A Frenchman, Buffon, suggested it back in the 18th century. A Scotsman, David Brewster, worked on it early in the 19th century. Fresnel won the prize because he experimented, built and put it together. Personally, I think Brewster should get more credit but that is because he did invent one of my favorite toys, the Kaleidoscope. His best contribution to the lens deal was to convince England to use the Frenchman’s ideas in their lighthouses.
As big as the lens in the Museum is, it would be huge if it were a conventional lens. By some very clever mathematics with prisms and angles the designers can collapse a huge spherical lens into that thing that will shoot light from a electric, or in the case of this lens, a whale oil lamp, as a beam 20 some miles in the sea so ships can see the location the lighthouse is built to locate. I wonder who built the lens that lets me see a star that is lightyears away.
But that is only part of the wonder of the Fresnel invention. This almost 200 year old invention has thoroughly modern uses. The light house version has a lamp in its middle and through its rings shoots a beam out. With a little reverse engineering you can collect light from a solar source, concentrate it onto a solar panel and you have a really good way to make “green” power.
Another use is in tail lights of cars. You can stamp all those ridges in circles into the plastic of the tail light cover and it will take that little bulbs light shine that bright red beam back a long way. They once used them in headlights but invention marches on and the have a different way now to make the headlight shine brighter as well as further.
Some of you have flat little magnifying glasses slipped into your wallet or purse. They use the Fresnel effect. If you really want accuracy of detail the full spherical curvature, rather than the flattened groovy ones, are better.
In any case, I doubt that Mr. Fresnel had any idea back then just how useful what he invented would be. It is also one of the things to remember when one looks at exhibits in museums. There is often quite an interesting story behind the exhibit you are being shown.
