Engineers of Dreams: Great Bridge Builders and the Spanning of America

by Henry Petroski

  The most sustained effort was begun in 1824 at Troy, New York, by Stephen Van Rensselaer, who, as lord of over three thousand farms totaling almost half a million acres in New York’s Rensselaer and Albany counties, was “the last patroon in full authority.” Van Rensselaer founded the Rensselaer School “to qualify teachers for instructing the sons and daughters of farmers and mechanics, by lectures or otherwise, in the application of experimental chemistry, philosophy, and natural history, to agriculture, domestic economy, the arts and manufactures.” By 1835, the Rensselaer Institute was authorized by the New York State Legislature to give instruction in “Engineering and Technology,” and the new degree of “civil engineer,” the first such in Britain or America, was granted that same year, to a class of four. By 1849, Rensselaer was the leading civilian engineering school in the country.

  In the South, engineering was taught at the University of Virginia, which Thomas Jefferson had established in 1814 to teach natural philosophy, military and naval architecture, and technical philosophy. The first course in civil engineering at Virginia was offered by one of the school’s original faculty members, Charles Bonnycastle, in 1833. He was joined in the newly established School of Engineering in 1835 by Barton Rogers, who in 1865 would become the first president of the Massachusetts Institute of Technology. Instruction in civil engineering was begun at the University of Alabama in 1837 by order of the board of trustees, who saw it as beneficial to the growth and maintenance of an increasingly important railroad network throughout the South. Among its first professors was Frederick Augustus Porter Barnard, who eventually became president of Columbia University. A School of Civil Engineering was begun at the College of William and Mary in 1836; Virginia Military Institute, which was modeled after the famous French Ecole Polytechnique, was started in 1839; and the Citadel was established in 1842 to teach both military and civil engineering.

  But young James Eads was in no position even to dream of attending such schools. The more common route to becoming an engineer throughout the first half of the nineteenth century was to work on a project like the Erie Canal, begun in 1817, “completed” in 1825, and widened, deepened, and extended in the 1830s, when it had become jammed with traffic. Accordingly, “many of the fledgling surveyors and assistants who planned and completed the canal ‘graduated’ from the project as highly skilled engineers.” Young men of more substantial means did go to Europe to study, rather than build, the great works of engineering, or specifically to France to learn engineering from a still more theoretical point of view. Many an engineer of the early nineteenth century also absorbed a great deal from his self-taught father.

  One such engineer was Loammi Baldwin, who became widely known for his hydraulic works, and who was responsible for the navy drydocks at Charlestown, Massachusetts, and Norfolk, Virginia. Even though it would be said that he had “learned engineering through self-study and by working under his father, Loammi Baldwin I, on the construction of the Middlesex Canal,” the younger Baldwin also studied mechanical subjects at Westford Academy, was a member of the class of 1800 at Harvard, and studied law. He practiced engineering before being admitted to the Massachusetts bar, then operated a law office in Cambridge from 1804 to 1807, and finally abandoned law to return to civil engineering. Following a visit to Europe to inspect public works, he opened an engineering office in Charlestown and became involved with the extension of Beacon Street beyond the Boston Common, the Union Canal, and other significant works. Though steeped in practical experience, he was also among the earliest of American engineers to call for state-supported schools to teach engineering theory.

  Baldwin spent the period 1824–25 in a concerted effort to enlarge his father’s civil-engineering library by augmenting it with British and French books, and he strongly advised that anyone “who would become an engineer must collect books.” Although the young James Eads was in no position to buy, let alone collect, books, he did have access to Barrett Williams’s library, where he could read well into the night. In this way, Eads, like many of his contemporaries, was able to lay the theoretical foundation for his own engineering education, which in his case would be completed on the river.

  In time, the elder Eads joined the family in St. Louis, and his general store prospered modestly. But the restless Thomas Eads, evidently not content with that business venture, went into partnership with another man to buy some property up the river, near Davenport, Iowa, where they planned to open a hotel. In the meantime, eighteen-year-old James had become a salesman at the dry-goods store and elected to stay in St. Louis, where he had some cousins, and where he knew he had a steady income and the run of a fine (if necessarily limited) library. Before too long, perhaps when he began to exhaust the resources of Barrett Williams’s books, James was drawn again to the river, and he signed on as a second clerk on the steamboat Knickerbocker. On a voyage, while rounding the bend from the Mississippi into the Ohio, the boat hit one of the countless snags in the water and went down.

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  The Mississippi River was notorious for claiming boats laden with personal and mercantile treasures, and Eads had had plenty of time while clerking on the Knickerbocker to reflect upon what was beneath the muddy waters. Many a person realized that whoever could salvage even a small fraction of the treasure sunk there could make a fortune, for shippers and insurance underwriters would pay anywhere between 20 and 75 percent of the net value of cargo salvaged, and anything sunk more than five years became the property of whoever could raise it. However, the treasure was elusive, for the constantly shifting sandy bottom of the river quickly covered up wrecks and their cargo and made them very difficult to locate—never mind to raise.

  When he was twenty-two years old, Eads conceived of a scheme that would enable a diver to work underwater for extended periods of time, thereby allowing him not only to walk about the river bottom and locate wrecks but also to free valuable cargo. Eads effectively worked as an engineer by developing, in his head and on paper, the early ideas for his “sub marine” and diving bell. What he had read in Barrett Williams’s books may have given him full assurance that enough air pressure could be pumped to a submerged diver to make the concept work, but since Eads did not possess the capital to realize the scheme by himself (a position quite familiar to engineers with dreams grander than their material resources), he took his design to potential investors and other entrepreneurs. In 1842, Eads approached Calvin Chase and William Nelson, St. Louis boatbuilders, and offered them a partnership. His investment would be the idea and the operation of the salvage craft, theirs the capital and experience to build the boat. They agreed, and Eads soon began the first of over five hundred explorations on the river bottom.

  Eads’s scheme involved the use of a modified snag boat, a double-hulled craft familiar on the Mississippi and so named because it was used to remove the many obstacles, or snags, that developed in the water. A diver was to descend to the river bottom in a diving bell supplied with air from the boat that served as the base of operations on the water. Divers had used diving bells successfully in calm lakes, and Eads engaged an experienced man to help him try out the scheme over a sunken barge loaded with about a hundred tons of pig lead. However, the swift currents of the Mississippi proved too much for the light equipment, and the diver found it difficult to maintain control underwater. Seeking a means of improving the operation, Eads went to the nearby town of Keokuk and obtained a forty-gallon whiskey barrel; he weighted its top down with a few hundred pounds of lead, and across its open bottom he attached a strap upon which the diver could sit. When the designated diver declined to use the contraption, Eads himself descended in what must have looked like so many mad Victorian inventions that would be illustrated years hence in the pages of Scientific American. He successfully gathered a quantity of lead into the barrel before signaling to be hoisted up, but by then he had ranged so far from the snag boat that the line to the derrick on the boat was overextended, and it capsized in the process. There were a few anxious m
oments before Eads was hauled to safety by hand, but once out of the water he commenced to modify the procedure and make improvements in the salvaging system. Future snag boats would carry not only an air pump but also a sand pump to expose wrecks and their cargo, in addition to heavy hoisting machinery to bring up safely the diver, the loot, and, in later modifications, whole riverboats.

  Not only did Eads and his partners make a fortune in the salvage business, but he grew to know the nature of the river bottom between St. Louis and New Orleans perhaps better than any of his contemporaries. He was intimately familiar with the stretch of river below Cairo, Illinois, where he once spent four hours a day for two months, Sundays excluded, walking back and forth over a three-mile stretch of the river, until he found the wreck of the Neptune. Years later, in his 1868 report as engineer-in-chief of the Illinois and St. Louis Bridge Company, he would write from experience of the action of undercurrents and other phenomena along the river:

  I had occasion to examine the bottom of the Mississippi, below Cairo, during the flood of 1851, and at 65 feet below the surface I found the bed of the river, for at least three feet in depth, a moving mass, and so unstable that, in endeavoring to find footing on it beneath the bell, my feet penetrated through it until I could feel, although standing erect, the sand rushing past my hands, driven by a current apparently as rapid as that at the surface.…

  It is a fact well known to those who were engaged in navigating the Mississippi twelve years ago, that the cargo and engine of the steamboat America, sunk 100 miles below the mouth of the Ohio, was recovered, after being submerged twenty years, during which time an island was formed over it and a farm established upon it. Cottonwood trees that grew upon the island attained such size that they were cut into cord-wood and supplied as fuel to the passing steamers. Two floods sufficed to remove every vestige of the island, leaving the wreck of the America uncovered by sand and 40 feet below low-water mark.…

  This kind of knowledge and experience would be invaluable later, when Eads had to determine how deep the piers would have to go to support a bridge over the Mississippi at St. Louis, and, still later, how to channel the waters at its mouth so that it would remain navigable past New Orleans and into the Gulf of Mexico. By observing the motion of the river bottom at many locations and under various conditions, he was able to formulate an unsurpassed theory of its behavior.

  When he was not working on or in the Mississippi, Eads would sometimes return to St. Louis to visit his cousins Susan and Martha Dillon, especially Martha, whom he wished to marry. Although the salvage business was profitable, her father questioned James’s financial and physical future in so risky an endeavor, and the marriage did not occur till 1845, after Eads had sold his part in the salvage business to invest in the land-based enterprise of running the first glassmaking factory west of the Mississippi. However, a poor financial climate and a scarcity of skilled workmen soon put Eads $25,000 in debt, and he returned to the salvage business in 1848.

  James and Martha had two daughters and a son, but the boy lived only about a year, and Martha died of cholera shortly thereafter, in 1852, leaving Eads heartbroken. He immersed himself in work and became very rich and famous, but soon his own health began to deteriorate, and he was ordered by doctors to take a complete rest. He married his cousin’s widow, Eunice Eads, traveled to Europe, and came back to work on the river again. After three more years, however, at the age of thirty-seven, with the Eads & Nelson Sub Marine No. 7 raising wrecks of all kinds, and with the salvage business one of the most prominent in the country, Eads became exhausted and was forced to retire. He did so in St. Louis, where he entertained some of the most famous visitors to the city and talked of politics, secession, and slavery, which Eads opposed. He did not agree with his second cousin, James Buchanan, who was then in the White House, on the Dred Scott decision, and when the Civil War came, Eads was happy that Missouri voted not to leave the Union.

  Soon after the surrender of Fort Sumter in 1861, Eads, the expert on Mississippi River craft, was summoned to Washington by his friend Attorney General Edward Bates, for a conference regarding the use of gunboats on the river. Eads recommended that a base be established at Cairo, Illinois, that Confederate commerce be blockaded, and that a snag boat be converted into an armed steamer protected by cotton bales. The proposal was referred to the War Department, but instead of a snag boat three wooden steamers were employed as the nucleus of the Mississippi fleet. Eads became the successful bidder to build seven five-hundred-ton, 175-foot-long armored wooden gunboats, whose hulls were to be divided into fifteen watertight compartments, and whose boiler and engines were to be protected with iron plates two and a half inches thick. Though the boats were supposed to be completed in two months, the last of them took over twice that time to finish.

  The first gunboat completed, the St. Louis, was launched on October 12, 1861, and fought in the battle against Fort Henry on February 6, 1862, thus predating the more famous battle between the ironclads Monitor and Merrimac by over a month. In the meantime, independent of the War Department, General John Charles Frémont ordered the conversion of two steamboats to ironclads. Thus Eads was able to implement his own plans to convert a snag boat, which resulted in the “most powerful of the western ironclads,” the Benton, with sixteen guns protected by as much as three and a half inches of iron. He later wrote to President Lincoln that “the St. Louis was the first ironclad built in America. She was the first armored vessel against which the fire of a hostile battery was directed on this continent, and so far as I can ascertain, she was the first ironclad that ever engaged a naval force in the world.”

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  Before the war, the Baltimore & Ohio Railroad had reached Illinois Town, later known as East St. Louis, Illinois, thus establishing a continuous rail line from the East to the Mississippi River. Proposals followed to build a bridge across the Mississippi into St. Louis, Missouri, thus opening a rail route to the West that would compete with the one through Chicago. It would be hard to say when exactly the first idea for a bridge might have crossed anybody’s mind, but as early as 1839 at least one engineer had not only thought about it but done enough preliminary calculations to write to William Carr Lane, the mayor of St. Louis, outlining a proposal for a bridge that would cost no more than 00,000 to erect.

  Charles Ellet, Jr., was born in Penn’s Manor, Pennsylvania, in 1810 and studied in Paris at the Ecole Polytechnique before commencing engineering work on railroads and canals in America. Around 1836, he turned his attention to the study of suspension bridges, perhaps inspired by the completion in 1834 of the 870-foot wrought-iron wire suspension bridge across the Sarine Valley at Fribourg, Switzerland, then the longest bridge span in the world. In 1842, Ellet would complete the Fairmount Bridge across the Schuylkill River in Philadelphia, the first suspension bridge in America to employ strands of wire rather than iron chains or eyebars to hold up the roadway, and in 1849 he would build the record 1,010-foot-span wire suspension bridge across the Ohio River at Wheeling, West Virginia. The deck of this latter bridge was to be destroyed by the wind in 1854, but in his 1839 proposal for St. Louis, Ellet had the utmost confidence in such designs.

  Upon receipt of Ellet’s letter, the mayor submitted it to the members of the St. Louis City Council with the request that a committee report on the proposal. Since the mayor noted that “Mr. Ellet promises leaving the city in a few days,” a speedy report was clearly his wish, and the joint committee of three delegates and two aldermen reported within six days. According to Calvin Woodward, dean of the Polytechnic School of Washington University, in his definitive history of the St. Louis Bridge published in 1881, the committee’s recommendation was to accept Ellet’s “proposition to make surveys and soundings, and to furnish full drawings and estimates, and present three hundred printed copies of the same to the city for the sum of $1,000.”

  Ellet evidently stayed on in St. Louis to investigate three possible locations for his bridge, all of which had rock on the St. Loui
s side of the river, thus ensuring firm foundations there. In midstream and on the Illinois shore, he found that the sounding auger could not be driven more than twenty feet below the water, and thus Ellet reported that the riverbed was “superior to the soil which sustains some of the most celebrated stone bridges in Europe” and firm enough to drive piles into for the foundations of piers. The proposed bridge was to have three towers, with a central suspended span of twelve hundred feet and two side spans of nine hundred feet each. The length of cables required would thus be within the limits of a suspension bridge, which Ellet calculated to be one and one-fifth miles, and for the Mississippi spans he specified ten cables, each comprising twelve hundred one-eighth-inch-diameter wires gathered into a cylinder of about five inches in diameter. Though the final estimate of $737,566 was less than 25 percent higher than the original one, which they seem not to have balked at, the mayor and City Council used cost as an excuse to reject what they must have feared was an overly ambitious technical scheme: “The time is inauspicious for the commencement of an enterprise involving such an enormous expenditure of money.” Their instincts were correct, of course, for, as Eads would soon discover on the turbulent bottom of the Mississippi River, the foundations of Ellet’s bridge would have been scoured away, possibly even before the cables were in place.

  The state of bridge building at midcentury was changing as rapidly as the bed of the river itself. As the railroads spread their routes throughout Britain, America, and elsewhere, they came to use ever heavier and more powerful locomotives to carry ever-increased loads, and thus the suspension bridge was generally thought to be too flexible and too susceptible to wind damage to be considered a viable and reliable railroad structure. This is what led Robert Stephenson, in the mid-1840s, to design and build in northwestern Wales a revolutionary bridge type of such massive proportions and strength that it carried trains not over but through its great tubular girders, which spanned almost five hundred feet between piers and about fifteen hundred feet total over the Menai Strait. The Britannia Bridge was a marvel of engineering, but it was an extremely expensive undertaking, costing a total of 600,000 pounds sterling by the time it was completed in 1850, and so improvements, by way of spanning similar distances with lighter structures, became imperative. Yet, though British engineers like Isambard Kingdom Brunel and Thomas Bouch designed lighter and lighter girder bridges that carried heavier and heavier railroad trains, the British generally shied away from the suspension bridge for railway applications. Some Americans, however, did not.