The Birmingham age-herald., 1907-10-22


 permanent one. Cast iron bridges came into use when railways became sure things. Italian engineers had thought of iron as a bridge material as carly as the sixteenth century, and England built one of iron in 1777. The first In America was at Frankfort, N. Y, in lSio, though Washington had correspondence on the subject as early as 1196. Now all America's bridges placed end to end would more than span the width of the continent.
 Bessemer's experiments msde steel cheaper than wrought iron and d new era dawned in bridge building A dls- tlnctive type has arisen in which the architect will have to consplfe With tue engineer before perfect bit ot art IS attained. For while stone bridge, Wl1h it's usual complement of moss and vines is always picturesque, and wooden bridge gathers grey hue from the weathery an iron or steel structure mas to be kept aggressiYely new in a coat of paint to protect it from the raVases of wind and rain. A German afehitecl claims that America has sacrificed beauty to utility in bridge making, but the most modern structures are disproving thls. American bridge builders lead the world. When the great Gokteik viaduct over the C,h,ln gzoune river in Burma was pro- iected it was American skill ana Amer ican steel that perfected 1t under tnA spur of English capital.
 The first use of steel in large arches in America was when Captain Eads hrideed the Mississippi at St. Louis. The manufacture of steel was not then so nearly perfected as it is now and the task was enormous. This was the hfst applcatio of the pneumatic process on a large scale, and it was here that phssi- | clans began making the first studE or | the effect of air pressure on the podles | of workmen in the caissons, marVelihs | over the great pressure, which they | found to be h pounds to- the square HIGH | and increasing with depth. Calssohs l had by this time superseded cofferdams | in pier building. and marked many cen tllries change since Queen Semirahs Hdo l deflected the course of the Euphrates .o | build her bridge and raise Babylon to | inc grandeur of Nnevoh. The St Lotus | bridge was begun in 1867 and nnlshed Ill l seven years at cost or Slo,VVv'VVo'
 | snenension bridges are very, very old. 1 Ants and monkeys in living chains gave l the idea to South American ana Airican II | natives, who developed 1t in vines anu boughs. Roeblng's famous bridge at Niagara was the first of the Kind Tn lhis country Then came one at fittspurs' and Cincinnati astouned the world Wl.ii one having a span of 10S5 feet. lheh ] poebline's Brooklyn bridge "the eighth wonder of the world" it was called, marked the climax of suspension bridge l work in the United States. It swung 1 clear of the waterway by l3o feet with central span of l59o feet, the largest Ill the world, though the projected Nor.i. river bridge expects to have a span ol nearly 5000 feet >-. The new East river bridge of New | York cost 80 900. The cables of steel 1 are of six tlmes~~the strength usuaily | reouirea and one the size Of man E | thumb will support car containing looo l men. The main cables are the size or barrel and cost s1,9sS,Ooo each, thous- ands of fine wires being woven into cyiino a lao | ders each of which can support oV,Vo'voo ] pounds. The foundations are laid iV i feet below water level and the two-story | nIatform. twice as wide as city street. | carries six trolley and elevated tracks | two wide carriage tracks, two bicycle | paths and two promenades
 In 1920 Ithlel Towne patented wooden | lattice bridge; in 1880 Long patented d | truss bridge called for him, and In ls4o | Howe an improved wood bridge Tor rall- ways When the Ohio was bridged in lstS 1 with a S2O-foot iron span the beginning l of long spans for railroads was marhed' 1 Since 1870 most railway bridges nave | reached a span of over o0os rect. me | Conemaughy Viaduct on the fehhsNi- 1 vania road and the Carrollton viaduct on | the Baltimore and Washington, famous Tn their day are now surpassed py more ! wonderful structures Improved facilities l have made quick work possible. Whoie | steel span was replaced not long ago on 1 the Pennsylvania road over the Schuyi- | kill at Philadelphia in 15 minutes, there being not a seconds delay In trains. l Brohe replaced the cables on Niagara
 in steel towers instead of errupting the traffic.
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