BRIDGE BUILDERS AND SOME OF THEIR ACHIEVEMENTS
In the old days when Rome was supreme a Caesar decreed that a bridge should be built to carry a military road across a valley, or ordered that great stone arches should be raised to conduct a stream of water to a city; and after great toil, and at the cost of the lives of unnumbered labourers, the work was done—so well done, in fact, that much of it is still standing, and some is still doing service.
In much the same regal way the managers of a railroad order a steel bridge flung across a chasm in the midst of a wilderness far from civilisation, or command that a new structure shall be substituted for an old one without disturbing traffic; and, lo and behold, it is done in a surprisingly short time. But the new bridges, in contrast to the old ones, are as spider webs compared to the overarching branches of a great tree. The old type, built of solid masonry, is massive, ponderous, while the new, slender, graceful, is built of steel.
One day a bridge-building company in Pennsylvania received the specifications giving the dimensions and particulars of a bridge that an English railway company wished to build in far-off Burma, above a great gorge more than eight hundred feet deep and about a half-mile wide. From the meagre description of the conditions and requirements, and from the measurements furnished by the railroad, the engineers of the American bridge company created a viaduct. Just as an author creates a story or a painter a picture, so these engineers built a bridge on paper, except that the work of the engineers' imagination had to be figured out mathematically, proved, and reproved. Not only was the soaring structure created out of bare facts and dry statistics, but the thickness of every bolt and the strain to be borne by every rod were predetermined accurately.
And when the plans of the great viaduct were completed the engineers knew the cost of every part, and felt so sure that the actual bridge in far-off Burma could be built for the estimated amount, that they put in a bid for the work that proved to be far below the price asked by English builders.
And so this company whose works are in Pennsylvania was awarded the contract for the Gokteik viaduct in Burma, half-way round the world from the factory.
In the midst of a wilderness, among an ancient people whose language and habits were utterly strange to most Americans, in a tropical country where modern machinery and appliances were practically unknown, a small band of men from the young republic contracted to build the greatest viaduct the world had ever seen. All the material, all the tools and machinery, were to be carried to the opposite side of the earth and dumped on the edge of the chasm. From the heaps of metal the small band of American workmen and engineers, aided by the native labourers, were to build the actual structure, strong and enduring, that was conceived by the engineers and reduced to working-plans in far-off Pennsylvania.
From ore dug out of the Pennsylvania mountains the steel was made and, piece by piece, the parts were rolled, riveted, or welded together so that every section was exactly according to the measurements laid out on the plan. As each part was finished it was marked to correspond with the plan and also to show its relation to its neighbour. It was like a gigantic puzzle. The parts were made to fit each other accurately, so that when the workmen in Burma came to put them together the tangle of beams and rods, of trusses and braces should be assembled into a perfect, orderly structure—each part in its place and each doing its share of the work.
With men trained to work with ropes and tackle collected from an Indian seaport, and native riveters gathered from another place, Mr. J.C. Turk, the engineer in charge, set to work with the American bridgemen and the constructing engineer to build a bridge out of the pieces of steel that lay in heaps along the brink of the gorge. First, the traveller, or derrick, shipped from America in sections, was put together, and its long arm extended from the end of the tracks on which it ran over the abyss.
From above the great steel beams were lowered to the masonry foundations of the first tower and securely bolted to them, and so, piece by piece, the steel girders were suspended in space and swung this way and that until each was exactly in its proper position and then riveted permanently. The great valley resounded with the blows of hammers on red-hot metal, and the clangour of steel on steel broke the silence of the tropic wilderness. The towers rose up higher and higher, until the tops were level with the rim of the valley, and as they were completed the horizontal girders were built on them, the rails laid, and the traveller pushed forward until its arm swung over the foundation of the next tower.
And so over the deep valley the slender structure gradually won its way, supporting itself on its own web as it crawled along like a spider. Indeed, so tall were its towers and so slender its steel cords and beams that from below it appeared as fragile as a spider's web, and the men, poised on the end of swinging beams or standing on narrow platforms hundreds of feet in air, looked not unlike the flies caught in the web.