Fresnel Lens

At the great northern elbow of California, in the days when the state's entire coastline was yet "lost," a stocky little lighthouse shouted a powerful warning to the Pacific. It is the great Fresnel lens of this lighthouse that is the subject of this narrative. On December 1, 1868, the 16-sided Cape Mendocino Lighthouse began to signal one white flash every 30 seconds by way of a slowly rotating, 16-sided first-order Fresnel lens manufactured by L. Sautter et Cie of Paris, France. The tower stood on top of a concrete-filled hole dug into rock at 425 feet of elevation.

Surely these were words spoken, or similar expressions of relief, gratitude, and amazement, for the better part of nine decades, as legions of mariners navigated around the deadly dangers of Diamond Shoals. For more than 25,000 nights, this light flashed from a lighthouse at Cape Hatteras, delivering its signal of assurance, caring, and guidance through the green-tinted crown-glass of its French Fresnel lens.

Historic Fresnel lenes are probably one of the most valued and admired artifacts in the lighthouse community. Mostly built in the 1800s, they are not only engineering marvels but also works of art. The industry faded away in the early 1900s, and even with today's technology, building a Fresnel lens is a challenge.

This is a continuation of the story of the Fresnel lens makers. In this article the Barbier, B6nard and Turenne (BBT) Company in France is described from its beginnings as a Fresnel lens maker for the world market, to its final demise when it was broken and merged into several other companies.

Louis Sautter (pronounced So-tay) completed engineering school at the Central School of Arts and Manufactures in 1846. Helped by one backer, Fernand Raoul-Duval, Sautter entered the navigation aids business in 1852, when he assumed ownership and management of the company that would carry his name. The business was previously wwned by Francois Soleil Sr., which by this time had passed from him to his son-in-law Jean Jacques Francois and ultimately to Francois' son-in- law Theodore Letourneau. The factory was then located at 37 Avenue Montaigne on the Champs-Elysees in Paris.

One might think this is a trick question, similar to "Who's buried in Granet's Tomb " There really was a question about the inventor of the famous lighthouse lens. From 1822, when Augustin Fresnel first published his paper Memoire sur un Nouveau Systeme d'Eclairage des Phares, Sir David Brewster, in Scotland, claimed that he was the true inventor, and his claims were not fully resolved until after his death in 1868. This story will discuss the various claims made by Brewster and the counter arguments made by Alan, David, Thomas Stevenson and others.

There are few things made by man that are more impressive or beautiful than a Fresnel lens. This crystal cage of glass sparkles in the sun splitting the light into tiny rainbows of glorious iridescent color like a precious diamond, and at night it sends forth its magnificent spokes of light to warn the mariner. Yet, all of this beauty comes from a mundane source, ordinary beach sand, with a few other ingredients, a process that was itself a bit of magic  rought by the hand of ancient craftsmen.