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Show i GETTING i M ACROSS - - -t j j j J ; ) I I l v i , getting i -M ACROSS - Celebrating the Opening of a New Bridge In Sydney, Australia. Bridges, or Lack of Them, Have Determined the Course of History Prepared by National Geographic Society, Washington, D. C VNU Service. 'THE completion of the new steel bridge across the Golden Gate recalls some of the old metal spans, many of which have been in use for two or more centuries. To England, in 1776, fell the honor of erecting the first iron bridge. There Abraham Darby cast a bridge at the Coalbrookdale Iron works and erected it across the Severn. Don Antonio de Ulloa describes various va-rious Inca bridges he found there. One of them, the. tarabita, is much like the greasy buttered bridge of Tibet. "The tarabita Is only a single sin-gle rope made of bejuco," says Ulloa, Ul-loa, "or thongs of ox hide . . ; This rope is fastened on each bank to strong posts. On one side is a kind of wheel, or winch, to straighten straight-en or slacken the tarabita to the degree required. From the tarabita hangs a leathern hammock capable of holding a man." Thomas Telford, a Scotsman who lived between 1757 and 1834, is known to students of engineering the world over for his achievements in canal, harbor, road, and bridge construction. He was engineer for the parliamentary commissioners for road making and bridge building build-ing in the highlands of Scotland, under un-der which organization 1,200 bridges were erected. In England he helped build five bridges over the Severn, and was employed on canals and highways by the Swedish and Polish governments. The Menai suspension bridge in Wales, connecting Carnarvonshire with the island of Anglesey, is the best-known monument to his pioneering pio-neering genius. It was opened in 1826, after seven years of work, and was, at that time, the world's largest larg-est suspension bridge, being 1,710 feet long, with a main span of 579 feet. Ancestors of Brooklyn Bridge. Telford was a shepherd's son. Apprenticed Ap-prenticed to a stonemason at fifteen, he studied engineering in his spare time and published verse. A man of amazing industry and versatility, Telford invented the pavement which bears his name.. Cables spun in place to swing a suspension bridge were tried in 1831 by Vicat, a French engineer, for a bridge across the Rhone. Later Roebling developed this method at Niagara Falls, Cincinnati, and final- Using another rope, the passenger pulls himself back and forth. Ulloa saw mules moved the same way. At Baghdad years ago, when the Turks were still waging their long war against desert tribes, their artillery ar-tillery used to lumber noisily across the Tigris on a bridge of boats, on its way to bombard some Arab mud town that had not paid its taxes. From a safe distance, when Turkish guns opened fire on the mud-walls guns opened fire on the mud-walled village, observers could see dust and timbers fly high into the air. Sometimes the Turks came back across the bridge of boats driving long lines of camels confiscated from delinquent nomads. One quiet, qui-et, very hot Sunday morning, the Bedouins, shooting and shouting, . rushed suddenly over the bridge, and stole their camels back again. At Mosul on the Tigris, hard by old Nineveh and in the shadow of Jonah's tomb, is another such bridge of boats. Millions of Shiah pilgrims have crossed these swaying sway-ing structures, carrying their dried and salted dead relatives and friends- to sacred burial grounds around the desert holy cities of An Najaf and Karbala. In Arabic Al Kantarah means "The Bridge." That old Roman bridge, the Alcantara, over the Ta-gus Ta-gus in Spain, stands today as proud and stout as when its huge arches were built, some 1,800 years ago. Bridge Into the Sea. Look at the mass, the heavy weight of these ancient bridges! They were built in, and for, one particular place. Today man cuts his steel bridges to order, ships them 5,000 miles, 10,000 miles, and erects them, by standardized practice, prac-tice, wherever they may be needed. The pieces are all shaped, numbered, num-bered, and packed in a ship's hold like the pieces of a child's construction construc-tion toy in a Christmas box; blueprints blue-prints are the "directions" for setting set-ting up! Rocketing from rain clouds on an air trip around Brazil, passengers come suddenly upon an enormous suspension bridge that seems to run out into the Atlantic ocean. It does. ly at the Brooklyn bridge. In Europe, as in America, the Nineteenth century saw vast advance ad-vance in iron bridge building, especially espe-cially stimulated by new railways. The Newcastle and Berwick railway alone required 110. Progress in design de-sign sometimes was costly. A new iron bridge across the Firth of Tay, near Dundee, Scotland, collapsed in a gale. Rushing at night into the open gap a mail train was wrecked, killing some four-score passengers. Today's bridge excels not only in design, foundations, and methods of erection, but especially in materials. I Now iron yields to steel. The Bessemer, Besse-mer, and later Siemens-Martin processes, proc-esses, gave bridge builders something some-thing new and stronger a steel cheaply produced. At any army field dav vmi mav 11 cunnecis tne mainland state of Santa Catharina with its capital, Florianopolis, which stands on an off-shore island. The American Bridge company erected this structure, struc-ture, shipping all the parts ready-made. ready-made. No other field in American overseas over-seas trade demands more ingenuity than does the bridge man's calling Orders come in for new bridges which may be wanted in any land from Alaska to Ecuador. No facts may be at hand about floods, river traffic, health and food conditions or the nature of the river bed and banks, whether rock, clay, sand or mud, at the spot where the new bridge is to be built. Since no tools, eaninmct see the speedy work of engineers, showing how emergency bridges are built, wrecked, and repaired in wartime. war-time. Washington Bridge Beats George. Homer tells about pontoon bridges used in war. Darius, Cyrus, Xerxes, Xer-xes, Alexander the Great, all employed em-ployed them. In 1781, it took General Washington Washing-ton four days to ferry only 4,000 men across the Hudson when he moved his army south from New York to Virginia. Now, over the George Washington bridge at New York, a whole army corps or 97,-000 97,-000 men, 23,105 animals, and more than 11,000 gun carriages, trucks, and other vehicles could be put across in eight hours! Chinese classics relate that a certain cer-tain king once crossed a river by walking over a bridge formed by ihe backs of a long line of big, accommodating ac-commodating turtles! In west China and Tibet, to this day, men "coast" across rivers on tightropes, sitting in a seat slung under the rope and sliding along it. To make the underslung seat slide faster the rope is often greased with butter. Dr. Joseph Rock, exploring for the National Geographic society, reports his own use of yak butler on such bridges. "I always tried to find a bridge made of new rope," says Dr. Rock, "for the rope soon wears out." In his "Vcyage to South America," Ameri-ca," written many iecades ago. building supplies of any kind may be available there, the American builder must take everything with Problems of language, food, and climate must be met. One American Ameri-can engineer arrived in Peru on his first visit to Latin America to build a bridge. Anxious to gain a Spanish vocabulary 0f brid words, he chose a personal helper from among the workers and practiced prac-ticed diligently. Imagine his chagrin cha-grin when he finally discovered that his bridge vocabulary could be used only in India, for he had picked a Hindu as a teacher! On another ob food shipments ,.ore so del d hat one American foreman was found subsisting on popcorn fricO with bananas. |
