Monsieur Fresnel’s Brilliant Invention

At the mouth of the Columbia River and along the coast of Oregon, there are many  lighthouses built on prominent headlands in the late 1800s by the former US Lighthouse Board. These historic buildings not only command fabulous views, but also represent a classic period of American architecture. After installing modern automated beacons on steel lattice towers in the 1960s, the Coast Guard began transferring the old structures to local groups that work to preserve them for future generations and keep open them to the public. All these lights have now been placed on the National Register of Historic Places. 

Each lighthouse was built a different design and height, but they all had the same type of lens. invented by a Frenchman named Augustin Fresnel (pronounced Frey-nell) who had made a remarkable scientific breakthrough in 1820 that dramatically improved inshore navigation. At the start of the 19^th century, new inventions like the steam engine and riveted iron construction were being tested by ship builders, but navigation still relied on simple aids to navigation that were only effective in daylight: a white flag on top of a hill or perhaps prominent trees with their branches trimmed and tops cut off. The first primitive lighthouses relied on giant oil-burning wicks with polished reflectors and only 20% of their light was actually directed towards the horizon, limiting the range to a few miles

In 1820, the French government commissioned a young engineer to investigate ways to increase the brightness of navigation lights. Fresnel had studied the new science of optics in his workshop and published a paper on the subject in a scientific journal. He realized that to achieve the necessary long range, a conventional convex lens of large aperture and short focal length would have been impossibly large. Within a few months, he had devised a “brilliant” and elegant solution that would make his name famous.

He reduced the amount of glass required by breaking it into a set of concentric annular sections known as “Fresnel zones.” At each zone, the overall thickness of the lens was decreased and each prism had a different angle. Together, these zones magically bent the light into a narrow focused beam. His invention was a scientific marvel of its time: a complex array of dazzling concentric glass prisms with a bull’s-eye lens at its center, all mounted in a gleaming brass framework that looked like a glass beehive.

The first full-scale trial was in the Cardovan Tower on the Gironde River in southwest France. Tests showed the Fresnel lens was five times as effective in capturing the light and could produce a beam of 80,000 candlepower. The light could be seen from more than 20 miles out.  A century later, when lights were electrified, it was found that a 1000-watt bulb shining through a first-order lens could generate a 680,000 candlepower beam! Fresnel’s system worked by bending and focusing the rays to form a single, concentrated beam of high intensity light.

The new lens was quickly put into production in Paris. It was so popular that it was offered in six sizes, called ”orders.” The weakest, the sixth order, was used in lights on lakes and in harbors while the largest, first-order lenses were used in major lighthouses on fog-bound coasts. A first-order lens, made up of over 1000 prisms, stood 12 feet tall, measured 6 feet in girth, and weighed 3 tons. It cost the huge sum of $12,000, plus shipping costs from France.

In Europe the new lenses were quickly adopted, but the head of the U.S. Lighthouse Board, Stephen Pleasonton, strongly resisted, feeling that it was just a fad. It was not until the 1850s that the first Fresnel arrived in the U.S, but its superiority was soon appreciated. The Columbia River was the scene of numerous shipwrecks in the 1800’s, and ended up with two major lighthouses within two miles. The first was the Cape Disappointment light,built in 1856– the first lighthouse on the entire west coast,

All of the early lighthouses were built to the same basic design: a Cape Cod house with the tower rising through the center. The design was simple, but delivering the materials to the site was often a challenge since they were perched on cliff tops with no access roads. In the case of Cape Disappointment, the first load of materials arrived on the bark Oriole in September 1853, but the ship wrecked directly below the cape on and the entire cargo, including the precious Fresnel lens was lost.

Two years passed before another ship arrived with the materials after weathering Cape Horn. A road was cleared to allow ox teams to pull wagons up the hill and construction began. The final cost was $38,500–a huge sum at that time.This made the entrance to the Columbia River safer, but captains of ships sailing south from Puget Sound complained that they could not see the light unless they stood far out to sea. In support of their argument, they cited wrecks of such ships as the Whistler (1883) and Grace Roberts (1887) on beaches north of the cape.

In response, the Lighthouse Board in 1893 dispatched a lightship to the mouth of the Columbia. Lightship No. 50, built at San Francisco’s Union Works, which took station four miles southwest of Cape Disappointment that same year. The 120-foot sail-powered vessel served until 1909 when replaced by steam-powered Lightship No. 88, which remained at the mouth of the Columbia for 30 years.

Also in 1909, the board asked Congress for $50,000 to build a first-order light to the north of Cape Disappointment, on the North Head, to give ships a third light to enable them to accurately fix their position regardless of their course when approach the entrance. Five years later, a 65-foot high tower of brick was completed. To distinguish the two towers in daylight, a distinctive black band was applied to Cape D in the early 1900’s, reminding us that visual identification is still important. The two lighthouses were both fitted with a Fresnel lens that can now be seen in a nearby museum.

The strongest light on the Oregon coast is Heceta Head on the central coast, 205′ above the water and visible for 21 miles in good visibility. This is the only light that still uses the original Fresnel lens.  It features 640 prisms and eight bullseyes. The government agency that built and ran the nation’s lights, the U.S. Lighthouse Service, disappeared long ago. (Another agency, the U.S. Life-Saving Service, manned the shore stations that were equipped with seaworthy rowing boats. The first life-saving station was built at Willapa Bay in 1877, followed by Neah Bay in 1878.)

Exposed to the worst of the weather, all these old light structures are showing their age, and the Coast Guard has found itself burdened with the task of historical preservation. However, this has begun to change recently, as they have been transferring ownership of all the lighthouses to the Washington State Parks & Recreation Commission or local bodies. This has the benefit of allowing the lights to be open to the public for tours, which are already available at the North Head Light,

Other lighthouses in Washington are also changing hands: the Westport Lighthouse with its elegant 107’ tower, properly referred to as the Gray’s Harbor Lighthouse, has been maintained by the local maritime museum since 2000. It featured a unique third order design with opposed red and white lenses. This light is the tallest lighthouse structure in Washington State. The museum also houses the best example of a first order lens: the impressive Destruction Island lens contains 1176 lenses, 24 bullseyes, stands eight feet tall and burned 2½ gallons of lamp oil (kerosene) a night.

The West Point Lighthouse SW of Shilshole Marina, also known as the Discovery Park Lighthouse, was turned over to Seattle’s Department of Parks and Recreation in October of 2004. West Point opened in 1881 with a fourth-order Fresnel lens. It was the first manned light station on Puget Sound and cost $25,000 to build. It was illuminated with a kerosene lamp until 1925, when it was connected to Seattle’s electric grid. And today, the Fresnel lens is still used in optical devices like traffic signals and overhead projectors.