IT WAS an arduous five-week Atlantic crossing in the late 19th century. The passengers were expecting to see land any day. Then a light appeared, a lonely star on the horizon. But it was not a star; it was a lighthouse. "At the sight of the light, we threw ourselves on our knees and gave thanks to God," a passenger later said. The light guided them safely to their destination.Not all those early voyages, however, ended so well. December 22, 1839, was a fair, sunny day on the New England coast of North America. The keeper of the lighthouse at Plum Island, Massachusetts, thought he could safely leave the island in his little rowboat, take his wife shopping, and be back before dark. But while they were away, a wind began to blow. A storm was coming, and fast. Soon sky and sea fused into a gray, howling mass of rain, foam, and spray. The keeper tried desperately to get back to the island but in vain. That night the lighthouse remained dark.
Near midnight, the ship Pocahontas, struggling to find the river and harbor entrance normally signaled by the lighthouse, searched in vain. Instead, the ship hit a sandbar. Its back was broken, and it sank with the entire crew on board. Just before dawn the Richmond Packer, heading for the same port, also came to grief, but only one life was lost, that of the captain's wife. Maritime history is replete with disasters that beacon lights might have prevented. "In olden times, many a ship was navigated safely across the ocean, only to be wrecked as it tried to make port," says the book America's Maritime Heritage. "The most dangerous part of an ocean trip was the last few miles, as a ship approached and finally sighted land."
According to lighthouse historian D. Alan Stevenson, between 1793 and 1833, the average number of ships wrecked annually on British shores increased from 550 to 800. More lighthouses were needed, as were better lights. In some countries, including England and the United States, sailing was made even more dangerous by the infamous moon cussers, villains who set up false lights to lure ships onto rocks, only to plunder them there. Survivors were often killed; moon cussers wanted no witnesses. Under a bright moon, however, their ploy would fail. Hence the name moon cussers. Eventually, though, more and better lighthouses helped put these thieves and murderers out of business.
The earliest mention of beacons is in the Iliad. "At the going down of the sun the line of beacon fires blazes forth," it says. The book Keepers of the Lights says that "the original beacons were nothing but huge fires of logs, sometimes kept in stone cairns, and later in big iron cages, that were allowed to burn out at frequent intervals with tragic results."
Then, about 300 B.C.E., on the island of Pharos, at the entrance to the harbor of Alexandria, Egypt, arose the world's first true lighthouse, the Pharos of Alexandria. A magnificent masonry structure between 350 and 400 feet high (about 40 stories), it was the tallest light-house ever built. One of the Seven Wonders of the World, it lasted about 1,600 years until it was toppled, probably by an earthquake. The Romans erected at least 30 lighthouses, from the Black Sea to the Atlantic. But when the empire fell, commerce slowed and lighthouses fell into darkness and disrepair. Construction began again about 1100. A celebrated lighthouse of the new era was the Lanterna of Genoa, whose keeper in 1449 was Antonio Columbo, uncle of explorer Christopher Columbus.
The first lighthouse erected in the open sea was a wooden one built by Henry Winstanley in 1699 on the treacherous Eddystone Rocks off Plymouth, England. He was proud of his accomplishment. While fishing from his lighthouse, says the video documentary Guardians of the Night, Winstanley would say: "Rise up, sea. Come and put my work to the test." One day in 1703, the sea obeyed. Winstanley and his lighthouse vanished without a trace.
Commemorating the friendship of the peoples of the United States and France, the 302-foot-high Statue of Liberty, in New York Harbor, doubled for some time as a navigational aid. For 16 years three keepers took turns keeping the flames bright in her torch. "From her beacon-hand glows world-wide welcome," says a sonnet at her pedestal.
Another big stride came in 1815 when French physicist Augustin-Jean Fresnel invented the most efficient lens ever to be used in lighthouses. Prior to Fresnel's invention, the best mirror systems—using Argand lamps, which remained popular for over 100 years produced about 20,000 candlepower.* Fresnel lenses boosted this to 80,000—about the same power as a modemday car headlight—and that with just a burning wick! (Now replaced by the candela. Previously, the international candle, measured in candlepower, was the luminous intensity of a light in a given direction as compared to that of a standard candle.)
Pressurized oil burners were invented in 1901, and it was not long before Fresnel units emitted up to one million candlepower. About the same time, acetylene gas came into use and profoundly affected lighthouse technology and automation, thanks largely to the work of Nils Gustaf Dalen, of Sweden. Dalen's automatic sun valve—an off and on switch that regulates acetylene gas flow by responding to sunlight—earned him the Nobel Prize for Physics in 1912. Electric filament lamps became popular in the 1920's and remain the chief illuminant to this day. When mated with a Fresnel lens, a bulb of just 250 watts can emit several hundred thousand candlepower. Nowadays, the most powerful lighthouse in the world, a lighthouse in France, can crack open the night sky with a blinding shaft of 500 million candlepower. A recent innovation is the xenon flashtube. It gives off a brilliant flash just millionths of a second long. Because the light pulse is so brief and intense, it stands out against a background of other lights.
Floating lighthouses, or lightships, were put to work where it was impractical to build a tower. Like towers, though, lightships have a long history. The first was a Roman galley commissioned in Julius Caesar's time. High on the mast, an iron brazier of burning charcoal lit up the night sky—and dropped embers onto the sweating bodies of the slave oarsmen chained to their stations below. The first latter-day lightship went to work in 1732 in the Thames estuary, near London. Thereafter, the number of lightships increased. For many years ships entering and leaving New York Harbor were guided by the lightship Ambrose. In recent years, however, lightships have given way to automatic light buoys and light towers, which are metal structures that resemble offshore oil wells.
Soundwaves, however, are subject to the vagaries of the atmosphere. Differences in temperature and humidity in the layers of air above the water can play tricks with sound, sometimes bending it upward, sometimes downward. Additionally, just as a pebble can be made to bounce on a pond, so a blast of sound can bounce right over a ship and not even be heard! But problems aside, acoustic signals can usually be heard miles away.
This article was taken from the Awake! January 22,1999