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Crossing the Mississippi

Inside the control room of a unique swing span

Photo: HENRY PETROSKI - students on Numerous campuses have benefited from Duane Ellifritt’s artwork.I recently traveled to the Quad Cities, an area that comprises Davenport and Bettendorf, Iowa, and Moline and Rock Island, Illinois. It was my first visit there, and I was grateful for the opportunity to learn firsthand about places I knew only indirectly.

When I was in graduate school at the University of Illinois, faculty members regularly flew up to the Quad Cities to lecture in extension courses taken mostly by engineers working at the Rock Island Arsenal and the John Deere Co., both of which remain major employers in the area. It was the pre-Internet age, and there were few alternatives to face-to-face teaching. Students in early morning classes the next day could guess which professor had taken the midnight flight back to Urbana.

The Quad Cities area is steeped in history, which my hosts were happy to relate. It was there in 1856 that the first railroad bridge to cross the Mississippi River was completed. Fifteen days later, it was struck by a steamboat and partially destroyed by the ensuing fire. Like most innovations, the bridge had met with opposition from those wedded to established ways of doing things. Steamboat interests strongly opposed the new mode of transportation, and they challenged the railroads’ right to obstruct the river. In a legendary court case, Abraham Lincoln defended the railroads against the riverboat industry. He lost the case in circuit court, but won on appeal in the U.S. Supreme Court.

Even before the bridge, the river had been difficult to navigate. The water was shallow and the rocky rapids hazardous. It was these conditions that led to the construction of a lock and dam, which at the same time removed one obstacle and introduced another. The original bridge was replaced by an iron one in 1872 and that by a steel one in 1896.

This bridge, known as Government Bridge, is historically significant on several counts. It was the first commission for the engineer Ralph Modjeski, who went on to design and build major spans across the country. The Rock Island bridge is a two-deck structure, with road traffic below rail. It is unique in having its swing span capable of rotating a full 360 degrees in either direction.

During my visit, I was given the rare opportunity to climb up to the control room, from where bridge and river traffic are monitored and the swing span is opened to allow boats and barges through the lock. This is a complex operation. Before the bridge can be swung open, all vehicle, foot, and rail traffic must be halted; rail joints uncoupled; and the ends of the 365-foot-long movable span freed from their bearings.

The centerpiece of the control room is a set of enormous hundred-year-old gears. Much of the structure and the machinery in the room is original, but it has over the years been repaired and supplemented with modern parts and equipment, including an air conditioner, television monitors, and, of course, computers. The bridge operator works more comfortably, safely, and efficiently now, but does pretty much the same things his predecessors did.

I don’t know how many Illinois professors might still travel to the Quad Cities, but I expect that if they do so it is more to consult than to teach. Understandably, most extension courses today are taught remotely, using online and video conferencing technology that has developed with the Internet and electronics industries. Yet to many an instructor, a course is still a course, involving lectures and quizzes. Whether in teaching a new course or operating a century-old bridge, technological upgrades do not necessarily change the fundamentals.

Henry Petroski, the Aleksandar S. Vesic Professor of Civil Engineering and a professor of history at Duke University, is the author of An Engineer’s Alphabet: Gleanings from the Softer Side of a Profession.




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