Brooklyn Bridge

The story of the Brooklyn Bridge is the stuff of legend and it would certainly by easy to focus the entire unit, if not a good portion of a semester teaching it in all its glorious details. For the purposes of this unit, however, it is only necessary to focus on certain significant elements that illustrate the basic historical trends of industrialization. The design John Roebling proposed that would satisfy the necessary criteria for crossing the East River was a suspension bridge of such size that it would remain the largest of its type in the world for 20 years after its completion. Its essential feature is a single uninterrupted span 1595 feet in length held 133 feet above the water at its highest point with no obstructions to navigation below it. The building of the bridge entailed two great technical challenges which should for the basis for the lessons on this bridge. The first was the building of the colossal stone towers that bear the entire weight of the bridge high enough for the necessary clearance beneath. The second was the construction of the four enormous cables with the strength to support the central span and anchorages strong enough to hold them in place. These two elements of the bridge, one working in tension and the other in compression, needed to be in balance for the bridge to stand. At 268 feet, the towers were certainly the "most conspicuous features" of the bridge, but the most compelling part of the story of their construction took place out of sight in the pneumatic caissons where the digging of the foundations took place. It is absolutely imperative that illustrations be used when teaching about caissons because they are so fantastic that they literally defy description. The best are contemporary sketches that appeared Harpers Weekly and Scientific American which show both cutaway drawings and illustrations of the type of work carried out by the men inside. One particularly dramatic photograph shows the immense size of the Brooklyn caisson prior to launching with the scale provided by the comparatively small men standing on top. Washington Roebling described the caisson as a huge diving bell built of wood and iron, shaped like a gigantic box with a heavy roof, strong sides and no bottom. Filled with compressed air, it would be sent to the bottom of the river by building up layers of stone on its roof. The compressed air would keep out the water and make it possible for men to go down inside and dig out the riverbed while the tower continued to be built on top. Eventually the caisson would reach bedrock at which point it would be filled with concrete and become the foundation of the tower. Using the drawings as a guide, the students should list all the technological advances that were necessary for the caissons to work. This should include steam power, air compressors, air pressure gauges, air locks and inventions specific to this task such as the ingenious method of removing the dredged material from the caisson without losing pressure or using time consuming air locks.

The actual work in the caisson however tells a different part of the story. Like most industrial workers of that era, the men in the caissons worked long hours six days a week under horrendous conditions for only two dollars a day. Only when the Brooklyn caisson reached a depth of twenty-eight feet did management decide that the work was so hazardous that the pay should be raised to $2.25 a day. That men would be willing to risk their lives in such obviously dangerous circumstances while putting their trust in a new and largely untested technology is astonishing. Although Washington Roebling was in fact very concerned for the safety of his workers and took all the same risks himself, his attitude was an anomaly for this era and may well have resulted in part from the continual public scrutiny his project was under. Students should understand that benefits for workers did not exist in this era so when laborers in the caissons did begin to suffer from the dreaded "caissons disease" (better known today as the bends) they received little more than short term treatment by the company doctor and then were simply sent home. If a worker's injuries were bad enough to make it impossible for him to work he was out of a job. Aside from the physical risks, working in the caissons was extremely unpleasant. The air was heavy and dank while the temperature never dropped below 80 degrees and was frequently higher. There was a constant stench from the black East River mud which covered every interior surface. Roebling's master mechanic, E.F. Farrington, describing the scene in the caissons said that "one might, if of a poetic temperament, get a realizing sense of Dante's inferno."

Under such conditions it is no surprise that the men in the caissons quit in droves. Over 2500 different individuals worked in the Brooklyn caisson from start to finish. That comes to about one man in three deciding to walk off the job or about 100 a week. What is surprising is that so many were willing to take their places. For every man who quit there were at least a dozen willing to take his place. Most of them were Irish, German or Italian immigrants so poor and desperate for work that they were willing to take any risk for almost any wage. Many were described as thinly clothed and undernourished which made their chances of enduring the conditions in the caissons less than likely. Students should consider all the circumstances that might lead a recent immigrant to take a such a job and write a first person fictional account of why the decision was made and what the work was like.

Only when the cases of the bends began to occur with increasing frequency in the Manhattan caisson did the workers attempt to improve their circumstances by going out on strike. Although it was the only time there was such a job action during the entire time of construction, the case is illustrative of what workers were up against when they tried to fight for their rights. The entire work force of caisson men refused to go to work on May 8, 1872. They stood out on the street nearby and demanded three dollars for a four hour day because the work had become so dangerous. The bridge company offered $2.75 a day but that was rejected the strikers and a worker who tried to break through their lines was badly beaten. After three days of negotiations, the director of the bridge company simply announced that any man who did not go back to work immediately would be fired. With that the strike ended as the men decided that it was better to take the risks at $2.25 a day rather than have no job at all. The best way to teach this lesson is with a role play. Students should be divided into four groups: one representing the bridge company directors, one representing the caisson workers, one representing unemployed immigrants looking for work and a final one representing "the public." After hearing a report on the recent cases of caissons disease, the workers group will take a vote to strike and explain their demands. The bridge directors should marshal their arguments and limit any offer to no more than $2.75 per day. The unemployed should make it clear that they are willing to work if the others refuse and should be able to explain their desperate reasons. The public meanwhile may be divided along class lines, but certain attitudes of the time should certainly be present. The basic philosophy of the time on these issues was Social Darwinism which taught that those who would compete for jobs such as those in the caissons are the least fit whose eventual demise would only be a benefit to society as a whole.

The story of the construction of the cables is useful to illustrate the fact that the bridge was being constructed at the very cusp of the age of steel. Students should note that the Brooklyn Bridge is the only East River crossing in which the primary supporting towers are made of stone. In the later bridges steel as a building material had matured to the point that it was the only reasonable choice. The cables, however, were to be made of steel and because it was such a new material the choice of which type of steel became a source of controversy.

Washington Roebling's initial specifications for the cable wire set forth certain strength and performance requirements without specifying how the steel was to be made. The lowest bid came in from his own family's wire company, John A. Roebling and Sons for wire made from steel manufactured with the new Bessemer process (Roebling had sold all his interest in the company to avoid a conflict of interest). Confidence in and knowledge of the Bessemer process was weak enough however that a certain individual with a financial interest in one of the other bidders was able to sow doubt about whether that type of steel was the best for the job. The older more expensive type of steel, crucible steel, was considered the finest grade and was used principally for tools. The contract for the cable wire was awarded therefore to the lowest bidder for crucible steel, but the reality was that no wire manufacturer could produce enough wire produced by the old method in enough quantity at the price quoted. The result was a fraud in which wire that had failed inspection, much of which was in fact made of Bessemer steel, was being switched with good wire and sent to the job site. Fortunately the Chief Engineer discovered the fraud before too much defective wire was spun into the cables, but Bessemer steel (now properly inspected) was the steel used after all.

 Those writing in support of the crucible steel should focus on the time tested nature of the method, the high quality of the steel produced and the question of whether the strength of the entire bridge should be dependent on a relatively new cheap mass produced steel. As one editorial writer observed, should the bridge be built with "the cheapest wire, or the best wire at the cheapest rate?" Those writing in support of Bessemer steel should point out that the method had been around for over 20 years, that it had been used extensively in building railroads, that it was the most economical and efficient method of steel production.

The method developed by John A. Roebling for "spinning" the cables in place is another excellent example of the technical ingenuity of this era. Construction of the cables had to be done in place to avoid obstructing river traffic and because once constructed they would be too heavy to pull to the tops of the towers. Pulled by a traveler rope strung over the tops to the towers, a loop of wire was pulled across and over the towers by a big iron wheel which thus laid two wires at a time. As a continuous loop, the traveler rope could carry two of these carrier wheels, one going each direction, at the same time. Like the caissons the system is difficult to describe without illustrations but I have not found any really good ones. The PBS video by David McCauley, Building Big: Bridges, has some excellent film footage, however, of this system being used on the construction of the Golden Gate Bridge. The basic method is so good that it is essentially the one still in use for the construction of suspension bridges today.

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