Show 7 za 1 1 7 6 J GETTING ACROSS I 1 Z J az 4 N A 1 P I 1 W 0 celebrating the opening ot of a new bridge in sydney australia bridges or lack of them have determined the course of history pre prepared ared by national society D C service THE HE 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 Coal brookdale iron works and erected it across the severn thomas telford a scotsman who lived between 1757 and 1834 Js known to students of engineering the world over for his achievements achievement in canal harbor road and construction he was engineer tor for the parliamentary commissioners for road making and bridge building in the highlands of scotland under which organization 1200 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 menal menai suspension bridge in wales connecting Carnarvon shire with the island of anglesey is the best known monument to his pioneering genius it was opened in 1826 after seven years of work and was at that time the worlds largest suspension bridge being 1710 feet long with a main span of feet ancestors of brooklyn bridge telford was a shepherds son apprenticed 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 a french engineer for a bridge across the rhone later roebling developed this method at niagara falls cincinnati and finally at the brooklyn bridge in europe as in america the nineteenth century saw vast advance in iron bridge building especially stimulated by new railways the newcastle and berwick railway alone required progress in design 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 fourscore four score passengers bridge excels not only in design foundations and methods of erection but especially in materials now iron yields to steel the bessemer and later siemens martin processes gave bridge builders something new and stronger a steel cheaply produced at any army field day you may see the speedy work of engineers showing how emergency bridges are built wrecked and repaired in wartime washington bridge beats george homer tells about pontoon bridges used in war darius cyrus xerxes alexander the great all employed them caesar built his 1400 foot wooden bridge across the rhine in ten days in 1781 it took general washington four days to ferry only 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 corp sor or men animals and more than gun carriages trucks and other vehicles could be put across iacross in eight hours I 1 chinesa classics relate that a certain king once crossed a river by walking over a bridge formed by the backs of a long lne line of big accommodating commo dating turtles lest 1 turkish and chinese bridges in west china and tibet to this day men coast across rivers on tightropes tigh tropes sitting in a seat slung under the rope and sliding along it to make the 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 butter on an such bridges 1 I always tried to find a bridge made of new rope says dr rock for the rope soon son wears out in his voyage to south america it written m any decades ago don antonio de ulloa describes various inca bridges he found there one of them the ta is much like the greasy buttered bridge of tibet the ta is only a single rope made of bejuco says ulloa 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 or slacken the ta to the degree required from the ta hangs a leathern hammock capable of holding a man 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 used to lumber noisily across the tigris on a bridge of boats 0 on n its way to bombard some arab mu mud d town that had not paid its taxes from a safe distance when turkish guns opened fire on the mud walled villages 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 q quiet ui i very hot sunday morning the bedouins Bedou ins shooting and shouting rushed suddenly over the bridge and stole their camels back agam again at on the tigris hard by old nineveh and in the shadow of jonass tomb is another such bridge of boats millions of shiah pilgrims have crossed these swaying structures carrying their dried and salted dead relatives and friends to sacred burial grounds around the desert holy cities of an najat najaf and barbala Kar bala bridge into the sea jn in arabic al A kantaras Kan tarah means the bridge that old roman bridge the alcantara cantara AI over the tagus in spain stands today as proud and stout as when its huge arches were built some 1800 years ago look book at the mass the heavy weight of these ancient bridges 1 they were built in and for one particular place today man cuts his steel bridges to order ships them miles miles and erects them by standardized practice wherever they may be needed the pieces are all shaped numbered and packed in a ships hold like the pieces of a childs construction toy in a christmas box blueprints are the directions no other field in american overseas trade demands more ingenuity than does the bridge mans 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 equipment or building supplies of any kind may be available there the american builder must take them with him |