For almost all the years that man has taken to the sea, shipwrecks were the norm, rather than the occasional happening. As brave and heroic the efforts of world-wide, shore-based lifesaving services were, shipwreck most often meant death for those onboard. Sadly, even if you could see the shore, and you were in a shipwreck, you didn’t know how to swim. No one did.
Not only that, the first “onboard lifeboat” or rescue vessel was first carried on an English merchant ship in 1894, way too late for so many souls.
Actually, only a few ships overpowered by storms were lost “at sea,” that is the open sea. Almost all ships wrecked by running into hazards closer to the shore, usually in the dark of night. As frightening as is the vast unknown of the blue horizon, mariners knew that it was land that would kill you.
It is impossible to really know how many ships went down, because governments did not keep records until the latter part of the eighteenth century. Horrifically, just in the narrow sea alley known as the English Channel alone, on the average during the early 1800’s, it is estimated that more than 250 ships were lost per year.
Hugging the coast, yet wary of the unseen hazards which lay in their path, seafarers were guided by local and recognizable on-shore landmarks during the day. Open fires on the beach or on a cliff were, no doubt, the earliest mariner’s night-time warning or welcome. We do know that Egyptians constructed the first known lighthouse, the Pharos of Alexandria during the third century B.C. During the Roman Republic and Empire, Rome’s Legionnaires, each and every one a mason as well as soldier, built light towers throughout the empire. Forever after, so did civilized countries which depended on international trade to prosper economically.
Not much changed over two thousand years. The Roman designed open-topped light towers dedicated to guiding ships at night. These “stone towers” burned whatever was most handy: wood, coal, dried vegetation soaked in tar, even olive oil. Later, and often tended to by monks, hermits, or religious penitents, the open fires were practically useless of course on rainy and windy nights.
History also tells us that in the late seventeenth century the Eddystone Lighthouse, built on a rock 13 miles southwest of Plymouth, England, had the first glass-enclosed lantern room. The light source was a chandelier of many one pound candles made of animal fat. At about the same time in Sweden, parabolic, polished metal reflectors set behind a light source were first used in a lighthouse. Toward the end of that century, mineral (kerosene) oil-fired lamps became the choice of fuel. However, the use of oil brought other problems to keepers like frequent trimming of the wicks and soot all over every surface, especially the polished reflectors.
A Swiss scientist, Aimee Argand, fundamentally transformed lighthouse illumination with his relatively smokeless, strong, and steady lamp set in front of such reflectors. His use of tubes of thin brass with a wick between forced a more beneficial flow of air circulation and evened the temperature, giving a more concentrated flame. Later, dozens of these Argand lamps would be used on large rotating wheels or “chandeliers” to allow lighthouses to exhibit flashing characteristics. Further, his and other’s use of a “convex glass magnifier lens” in front of the light source and a reflector behind helped a bit more. The invention and use of Argand’s lamps was a step in the right direction, but not the complete answer.
Even with the best of polished mirrors, improved flow of air, fuel, and curved glass, the Argand apparatus loses more than half of its light due to dissipation. Light waves, as we now know them, radiate from the light source. Light waves, unless harnessed and focused, scatter above and below where light from a lighthouse lantern is supposed to go – straight out to sea. This was the real dilemma. was that in its hands-on application atop a lighthouse in a lantern room, there was the nightmare of the proper geometry of alignment of the many mirrored surfaces, each with a single light from whatever source, fronted by a “magnifier.” Needless to say, maintenance of these clumsy apparatus by keepers was difficult. And as end result, mariners were still pretty much unable to use or even see most of the lights which existed. The consequences remained as deadly, as shipwrecks continued to occur with calamitous regularity.
While improvements in the mixture of air and fuel, plus the use of glass and reflectors had somewhat of an impact on the quality of the light produced from the top of the towers, the biggest practical problem remained. How did one harness the light produced, and especially the light lost, in order to “aim” it straight out from a lighthouse in the direction of ships out to sea?
Augustin-Jean Fresnel Changes Everything
In an era of revolutions, political, economic, industrial, technical, and scientific, a sickly second son, Augustin Fresnel, was born in Broglie, Normandy, France to his successful architect father, Jacques Fresnel, and his mother, Augustine, the daughter of an influential lawyer. Augustin was raised in a strict religious home.
A frail and consumptive childhood augured a lifetime of ill health. He died of the disease at the age of 39. By the age of eight, he could barely read his native French, and never mastered the scientific languages of the time: English and Latin. He was, according to family legend and his teachers, a slow child, behind in his lessons. He had difficulty with words and communication, and seemed to have trouble with the concepts of the “classical” education. It is said that his childhood learning style presented today would be identified as autistic. Quite by luck, he was sent to accompany his older brother, Louis, the most scholarly one in the family to Caen, to study at a science-mathematics school. Despite his inability to communicate easily, he showed remarkable mathematical proficiency and he frequently astonished his teachers. In 1804, he and his brothers were selected to attend Ecole Polytechique in Paris, the best of all French engineering universities. It was here that he flourished at geometry, graphic arts and technical drawing. In this, the Napoleonic era in France, many of Fresnel’s classes dealt with artillery and plotting strategy, chart and map making, and geography. Since he was not considered robust enough for the rigors of military life, Fresnel, was selected to attend the French National School of Bridges and Highways, the world’s oldest school of civil engineering.
After completing his studies, Fresnel was assigned by the government to repair canals and highways. Napoleon was especially concerned with a new network of roads which would enable his soldiers to easily travel the length and breathe of France in order to put down revolts and show when necessary the Imperial flag. Fresnel worked hard at his projects and did well, but was uncomfortable in communicating with the men working for him. On his own and in collaboration with family members, he continued with scientific research, specifically experiments with light and optics.
At the time, opposition to Newton’s theories was considered sacrilegious
At that time, the world-wide scientific community embraced the theories espoused by Isaac Newton. Fresnel’s professors at the Ecole Polytechnique were strict adherents of light as a particle or a “swarm of tiny corpuscles” moving through Aristotle’s “ether.”
For a hundred and fifty years, scientists ignored the problem of Newton’s problematic investigation of diffraction. No one, including Newton was able to successfully explain it. Fresnel believed that he could shed light on the issue by considering light as a wave rather than a small particle. This was highly unorthodox and contrary to the accepted Newtonian theory of the day. Fresnel sent his ideas in the form of an essay to Andre Ampere (the physicist from whom we get the term ampere). Deliberately or not, Ampere lost the unread essay. However, young fellow-physicist Francois Arago, a member of the French Academy of Science, welcomed Fresnel theory, urged Fresnel to continue on with his study, and began to champion it.
Over the next two years, turmoil in France worked in Fresnel’s favor freeing him for a time from his mundane “day” job. Even without access or the benefit of accurate, sophisticated scientific instruments, Fresnel began working on experiments. His correspondence succeeded in convincing several prominent French scientists that he was on to something of a breakthrough in light and optics. From time to time, he also was relieved of his highway duties and brought to Paris to work with more state-of-the-art instruments. One setback was the submission of a paper which strongly disputed Newton’s theories. Again, the mere suggestion to scientists of the time that Newton was wrong was considered blasphemy. As a punishment, Fresnel was transferred two hundred miles to a menial job overseeing a workhouse for the indigent and debtors.
Finally, some of his theories began to gain acceptance and he was transferred closer to Paris. His classical papers of 1819 and 1821 succeeded in convincing many skeptics. He was appointed Secretary to the Commissioner of Lighthouses in 1819, and while still responsible for some road and canal design, he was able to devote much more time to his work with lighthouse illumination.
The Fresnel lens is Invented
In 1819, Fresnel first proposed a practical and urgently needed application of his theory of light traveling in waves. The world needed someone to build a lighthouse light apparatus that sailors could actually see, something other than the balky collection of mirrors and smoke. He theorized that if he replaced reflectors with lenses to reflect and refract light waves lost due to the problems with just mirrored surfaces, it would certainly work. Fresnel also correctly thought a lens of glass would be more efficient than a mirror taking all the light from a source and directing it into a beam. Yet, there were problems with this: the sheer weight of such a giant single piece of glass, and theoretically, the distance to place it from the light source. His answer to the dilemma to was “stack” concentric sections of individual prisms or triangles of glass mathematically aimed to catch the light waves, bend the waves and force the light waves straight out in a steady, parallel lines. The group of separate prisms collectively would do the job of a big lens, and yet weigh much less. He called this concept “step lenses,” made with segments of rings of prisms.
To convince the French Lighthouse Commission, he knew he had to construct a model or even a lens that worked. His next and truly most vexing problem was the quality of glass available to him. Flint glass was at the time the choice for optics. Flint glass is also known as leaded crystal, and because of its high lead content, was almost perfect save for the fact that it was heavy and dense. The total weight of a lens, especially one that had to move or rotate in place, at the top of a lantern room was a concern. Fresnel chose what is called crown glass. It was hard, lighter than flint, had fewer bubbles and imperfections, and was easier to mold. For the lens to work both scientifically and realistically, he needed glass shaped and in sizes and forms that had never been manufactured before by anyone in the world. Fortunately, he had the help of a superb Parisian optics and instrument maker, Francois Soleil, in fashioning the lens. Fresnel first used rectangular panes of crown glass, thinking that they might be cheaper and more easily manufactured than curved ones, but he was soon convinced that curved ones could be made almost as cheaply. Soleil actually perfected a method of reheating the glass, still not entirely understood today, in molds which eliminated most of the blemishes.
Next, Fresnel worked on the light source, a lamp needed to be as brilliant, and efficient as possible, but also small in size. Along the way, he discovered that several concentric wicks in a lamp emitted a brighter light than a single one, and used about the same amount of oil.
In his own words (and echoed by all who saw Fresnel’s demonstration in March of 1820 of his single lens panel), the members of the Commission of Lighthouses were, “dazzled by the spectacle I gave them.” The single panel worked so well that the chief commissioner immediately ordered a full apparatus be constructed of seven identically shaped and sized panels to be arranged in an octagon surrounding the light source.
Friday, April 13th, 1821 certainly could have been an inauspicious day to try out the eight-sided, new invention, especially one which disputed Newton’s laws, had it not been for the fact that the single test panel of the year before far out-shown all forms of reflectors. Huge crowds of Parisians including the entire membership of the Commission of Lighthouses, as well as sailors, and curious citizens were gathered at opposite ends of the city, some at the Paris Observatory and some on the distant hills of Montemarte. The event was staged as a competition between manufacturers of “new and improved” mirrored reflectors and Fresnel’s lens. Everyone in attendance marveled at the brilliance of the Fresnel lens. The Argand type reflectors, dim in comparison that night, and in use in lighthouses world-wide, were now rendered completely obsolete.
(As a side note, European lighthouses were quick to adopt the Fresnel lens. Because of the politics involved, stubborn resistance to change, and costs, the United States Lighthouse Establishment continued using the Argand-Lewis Lamp reflector design for another twenty-five years despite the universal condemnation from American mariners who sailed to Europe, saw the lights, and traveled back home to the dismal light from American lighthouses.)
Cordouan the “Versailles of the Sea”
The entrance to the Gironde River, the waterway to the interior of southwestern France, is flanked by two narrow channels alive with hidden reefs, outcropping rocky ledges, and shifting sand banks all completely submerged at high tide. At the mouth of this river, on an island of danger, sits the Cordouan Lighthouse, arguably, the Most Beautiful Lighthouse in the World. Cordouan is four and a half miles out to sea in the middle of the swift, ever-shifting ocean currents, even more bedeviled by the estuary action. Since shipping began, this area has menaced sailors attempting to thread their way to the ancient port of Bordeaux up river, to participate in the wine trade.
The Cordouan Lighthouse stands at 223 feet, to this day, one of the ten tallest traditional towers in the world. Called the Patriarch of Lighthouses,
Le Tour de Cordouan is also the oldest of French lighthouses still operating.
Cordouan’s interior décor is decidedly ornate, even for the period in which it was built. All done in marble, the ground floor contained four apartments for keepers; the second story contained an apartment for King Henry IV of France, and the third level contained a chapel, replete with an altar, four stained glass windows and a domed mosaic. Every floor contains a profusion of gilt, carvings, elegant arched doorways and Renaissance statuary.
Fittingly, it was here that in the summer of 1823 that Augustin Jean Fresnel, despite deteriorating health, personally oversaw the installation of the first Fresnel lens in Cordouan’s lantern room. Lit for the first time on July 23, 1823, this First Order dioptric ushered in a whole new era in safety and navigation for ships. The lens produced an intensity of light far surpassing anything else ever seen, and could be seen some 17 miles out to sea.
In 1854, Fresnel’s first lens was removed and replaced by an updated Fresnel lens which is still in use today. The historic first Fresnel Lens is now safely on exhibit at The Mussee des Phares et Baluses on the Island of Quessant off the coast of Normandy.
In 1862, the Cordouan Lighthouse was designated as one of the first two buildings in France to be classified as a national historic monument. The other monument named that that year was the Cathedral of Notre Dame in Paris.
The winter before, Fresnel produced another series of papers which would provide the framework for much of the Physics of the nineteenth century. Honors from many countries including France’s own Legion of Honor came to him. Fresnel continued to directly supervise the construction of newer lenses and clockwork mechanisms. Since the Fresnel Lens concept was so uniquely his, his personal involvement was necessary in travelling to many of existing lighthouses all along the coast of France. The winter of 1826 saw his cough worsened and his lungs weakened. Fresnel’s symptoms today are recognized as tuberculosis. He became more frail, and died at the age of thirty-nine on Bastille Day, 1827. His chief regret was that his illness and decline took him away from his sense of duty to France and Science. He wrote in the spring of 1827, “I could have wished to live longer, perhaps I might have had the happiness of finding the answers to some [more of these questions].”
The Basis for All Modern Optics
The Fresnel Lens is considered by many to be one of the major inventions of the 19th Century simply because it enabled lighthouses to function to the best of their ability, thus paving the way for safer shipping of goods manufactured during the Industrial Revolution. If you could safely transport goods manufactured in a country overseas to another without fear of shipwreck, the benefits to the worldwide economy and commerce was immeasurable. The lens and Fresnel’s theories mark a departure so radical in thinking that it helped bring about brought the use of concentrated light waves, or lasers, as a tool in medicine, communication, warfare, sensors, bar scanners, and even measurement of distant objects in space.
Fresnel’s lens is still so highly thought of, that his bust is displayed in every French lighthouse. While he was personally supervising the placement of lenses in French lighthouses, he shared his discovery with Robert Stevenson, the Scottish engineer who visited Fresnel and took careful measurements of the lens at Cordouan, and ordered two lenses for the United Kingdom. Stevenson and his family, including his grandson, Robert Louis Stevenson, designed and or built more than one hundred of England’s, Wales, and Scotland’s lighthouses.
