Tuesday, May 19, 2009
The Great Bridge
Among the topics for term papers that I provide for my students is a list of New York City landmarks. By far the most popular every semester is the Brooklyn Bridge. I've probably read a score of papers of widely varying quality on the Bridge for this semester alone, and I still have more to go. I'm always amazed at how little my students know about their own city, and how little they've seen of it.
I presume they like the Bridge because it's familiar to them, it's still the most spectacular span across the East River (the Williamsburg is slightly longer. but it's such an ugly duckling compared to the Brooklyn), and because its construction history is so dramatic.
Crossing between New York and Brooklyn used to be very difficult with constant ship traffic, irregular ferry service, and worst of all, ice floes in the winter, like those on the Hudson river pictured above.
John Roebling, an engineer from Germany, first got the idea for the bridge while stranded in a ferry caught in the ice. He watched frustrated people risk their lives trying to walk across the moving ice to shore.
Roebling persuaded the City of New York and the City of Brooklyn that a bridge over the East River was a matter of necessity with traffic increasing between the 2 rapidly growing cities. He drew up plans for a massive suspension bridge, the largest yet built, and the first to cross 2 relatively level land masses rather than over a chasm or valley. Roebling invented steel cable which he used in previous bridge construction projects with great success. Steel cable proved to be much stronger than the iron chains used in earlier suspension bridges.
While surveying the site for the future bridge, an arriving ferry boat from Manhattan crushed John Roebling's foot against the dock. He died of tetanus days later, fatally demonstrating the need for a bridge. His death brought to a halt plans to build the bridge.
His son Washington Roebling, still a young man just out of the military, took over the design and construction of the bridge.
The first things to be built were the two great towers on either side of the river. The first stage in that construction was the construction of great wood and iron caissons; huge structures as high as the river was deep that were water sealed and bottomless. They were built in the Brooklyn navy yard and towed out and sunk over their respective sites on the Brooklyn and Manhattan side. Compressed air was pumped into the chamber at the bottom to keep out the river water. Construction crews cleared out the mud and rock from the bottom by hand, digging down to bedrock. As crews dug below, the stone and concrete base of the tower was built on top. When the caissons reached bedrock, the work chambers would be filled with concrete.
Work inside the caissons was dark and dangerous. Most of the men who worked excavating the foundation were Irish laborers paid pennies per day. There was the constant risk of fire and flooding. One of the caissons did catch fire. The fire was so intense and spread out through the wooden hull that the caisson had to be flooded to extinguish it.
An even worse danger came in the form of "caisson's disease." Perfectly healthy men would suddenly start vomiting and convulsing. Some would end up partially paralyzed, others died. This was "the bends" caused by the sudden change in air pressure when emerging out of the caisson. Nitrogen bubbles would form in the blood, causing convulsions and excruciating pain. Washington Roebling himself would be permanently invalided by "caisson's disease." He frequently visited the caissons, sometimes working beside the laborers.
Washington's wife, Emily, became the de facto supervisor and chief engineer of the project after her husband became incapacitated.
When completed, the towers were the tallest buildings in the city, and the first structures to top out the spire of Trinity Church, previously the tallest structure in the city. Then came the task of building the cable web and the 135 foot high span across the river. This work was slowed by corruption and by catastrophe. Much of the cable had to be remade and rebuilt when it was found out that a corrupt manufacturer cut corners and shorted the quality of the steel in some of the cable. Worse happened when one of the cables suddenly snapped, killing 2 men and injuring several more. A total of 27 men died while building the Brooklyn Bridge.
The completed Bridge was opened on May 24, 1883, Queen Victoria's birthday. Emily Roebling was the first to cross, leading a delegation including the governor of New York, the mayors of New York and Brooklyn, and the President of the USA, Chester Arthur (who?). They crossed the bridge to congratulate the bedridden Washington Roebling at his home on his accomplishment.
A lavish fireworks display lit up the night sky, followed by electric lights illumining the bridge for the first time.
The Irish laborers were not invited. Some boycotted the festivities because of the concurrence with Queen Victoria's birthday.
On May 30, 1883, over 20 people died in a panicked stampede on the bridge when a rumor spread that the bridge was about to collapse.
As you can see, the bridge didn't collapse.
John Roebling always intended the bridge to be a great work of art as well as a prodigious work of engineering. In the design of the towers, he used the pointed Gothic lancet arch to invoke the memory of those earlier accomplishments of engineering and collective enterprise, the medieval cathedrals. A great steel web between 2 stone towers holds up the span across the East River forming one of the most stirring structures ever built in New York.
Most of the information in this post comes from several semesters worth of student papers on the Brooklyn Bridge. See? You can learn from your students.
Posted by Counterlight at Tuesday, May 19, 2009