James Eads was an anomaly among bridge builders, in that his involvement with the genre began and ended with a single example, albeit one of historic proportions. His first and most ardent love was the Mississippi River itself, and he appears to have backed into bridge building more because of his civic involvement with the mercantile movers and shakers of St. Louis than because of any long-harbored dream to build a bridge greater than any other. Eads was, however, a consummate engineer, and once he got involved with the problem of bridging the Mississippi, it was as driving a challenge as was raising wrecks from the river’s bottom or channeling the river itself to the Gulf.
Most engineers involved with bridge building in the late part of the nineteenth century and the early part of the twentieth could not have such a fleeting romance with iron and steel. With the railroads continuing to expand and to increase the power of their locomotives and the size of their rolling stock throughout this period, there was a constant need for stronger, larger, and more innovative bridges, and for engineers to do everything from creating their designs to putting up their superstructures. In America, these engineers were by and large of a different generation from Eads. Theodore Cooper was to be among those of the newer generation who rose to the top of the profession and became involved with building what would have been the greatest bridge in the world.
Theodore Cooper, as a member of Rensselaer’s Class of 1858 (photo credit 3.1)
Theodore Cooper was born in 1839 in Cooper’s Plain, in the western New York State county of Steuben, which would give its name to the finest products of the Corning Glass Works, now located nearby. Unlike Eads, who came from an itinerant family with a precarious financial future, Cooper was born into one of permanence and purpose. The son of John Cooper, Jr., a practicing physician, and Elizabeth M. Evans, young Theodore was one of nine children who grew up on land their parents settled on shortly after their marriage in Pennsylvania. The Coopers, among the earliest settlers of Steuben County, developed an estate there on land inherited from the elder Cooper’s maternal grandfather. When young Theodore decided that he wanted to study engineering, he did not have to rely upon a benefactor’s library for books. Rather, he traveled about 150 miles east-northeast to attend Rensselaer Institute and study toward the degree of civil engineer in that still-young institution. He graduated in 1858, in the class after Washington Roebling, who was two years older.
Washington Roebling was, of course, the son of a famous engineer, who not only served as the young man’s mentor but also provided him with opportunities to gain invaluable work experience as an assistant on such projects as the Allegheny suspension bridge in Pittsburgh and, after service in the Civil War, on the bridge between Covington, Kentucky, and Cincinnati, over the Ohio River. Such privileged apprenticeships prepared Washington Roebling well to take over construction of the Brooklyn Bridge after his father died. Beyond his Rensselaer degree, Theodore Cooper had no such personal entrée into engineering. Rather, he started his career as an assistant engineer on the Troy & Greenfield Railroad and on the Hoosac Tunnel project in northwestern Massachusetts.
A tunnel through Hoosac Mountain, which would be an important link on the route between Albany and Boston, had been proposed as early as 1819. In 1825, the younger Loammi Baldwin had identified a location near North Adams, Massachusetts, at which a five-mile tunnel could be driven almost due east through the mountain at a cost, he estimated, of no more than a million dollars. At the time, this was too dear for the Massachusetts Legislature, but the Boston & Albany Railroad Company began the task in 1848. It was expected to be a five-year project, but that was overly optimistic. In 1856, when little progress had been made, Herman Haupt, a seasoned engineer who had been trained at the U.S. Military Academy and gained much experience on railroad bridge and tunnel projects, was prevailed upon to help with the Hoosac Tunnel, by raising funds for it as well as overseeing its completion, and he resigned from the Pennsylvania Railroad to do so. It was in 1858, the year Haupt attacked the mountain with renewed vigor and with an improved pneumatic drill, that Theodore Cooper came on board to begin his engineering career. After three more years of work on the tunnel, however, it was only 20 percent complete, and, amid charges of corruption and mismanagement, the commonwealth of Massachusetts took over the project. With the outbreak of the Civil War, Cooper, who had risen to the position of assistant engineer, left the tunnel project to join the U.S. Navy. (The tunnel was not to be finally blasted through until 1874. After it opened to rail traffic the next year, its route could be advertised as the “shortest line between the east and west.”)
As an assistant engineer in the navy, Cooper was ordered to the gunboat Chocura, then still under construction in Boston. He spent almost four years attached to the Chocura, which saw action at the siege of Yorktown and the battle of West Point, served as a guardship on the Potomac, and took part in the blockade off Fort Fisher and along the Texas coast, among other campaigns. Cooper was ordered to the Naval Academy, then at Newport, Rhode Island, in June 1865, and then to Annapolis, Maryland, where the academy reopened that fall, as an instructor in the recently formed Department of Steam Engineering. He was in charge of all new construction at Annapolis for the three years he spent there, then undertook a two-year tour of duty in the South Pacific on the Nyack. Finally, after returning to Annapolis for two more years, he resigned his position as first assistant engineer to work for James B. Eads, with whom he may have become acquainted during the latter’s many trips to nearby Washington.
Cooper was appointed by Eads in mid-1872, first as inspector of the steel being made at the Midvale Steel Works, and later as inspector of construction at the Keystone Bridge Company, where the parts were finished and tested before being shipped to St. Louis. These were important responsibilities; if the steel was not made to specified standards and did not have the same strength and flexibility as assumed in the design calculations, then all the engineering predictions of the finished bridge’s behavior were invalid. Such assignments in Pittsburgh were common beginnings for promising young engineers, but Cooper was already approaching his mid-thirties, and he must have been anxious for even more responsible work. By the end of the year, he was sent to the construction site in St. Louis to supervise the erection of the parts whose quality he had assured, and it was in this position that his reputation among bridge builders became more visible.
When Cooper arrived in St. Louis, the superstructure of the bridge was well along, the trussed ribs arching almost one hundred feet over the river. Walking about on the incomplete superstructure must have been nerve-racking and was certainly dangerous, but Cooper gained a reputation for personally inspecting the erection of the superstructure daily. Indeed, he was absent only on one “wet, snowy day, when everything was covered with ice,” because he was “too stiff in the joints” from a fall he had taken a few days earlier. According to Cooper’s own account, he “tripped on an unbalanced plank” and fell ninety feet into the river, but “escaped uninjured, excepting a stiffness resulting from the shock.” He afterward elaborated on the incident to Calvin Woodward, the principal historian of the Eads Bridge, who related the story as follows:
He was conscious (he said) of its taking him a long time to fall 90 feet. He thought of the probable force with which he would strike the water, and rolled himself in to the shape of a ball as much as possible. He struck the water he hardly knew how, and went very deep into the river,—nearly to the bottom, he thought. After what seemed another long interval, he reached the surface and struck out vigorously for shore. He then found that he still held in his hand the lead-pencil which he was using when he stepped on the treacherous plank. A boat from the East Abutment soon picked him up. In an incredibly short time he changed his clothes and walked into the office of the company as though nothing had happened.
Several weeks after his fall, Cooper examined a tube that a workman had reported broken and found another tube broken also. With Henry Flad sick in bed at the time, Cooper ordered emergency measures taken to keep the unfinished bridge from collapsing, and he telegraphed Eads in New York of the alarming development. Eads first wondered if all their calculations had been in error, and if somehow extremes of temperature were straining the metal beyond its limits. After reflection, however, he recognized that relaxing somewhat the cables supporting the unfinished arches would relieve the tubes in the arch ribs of part of the strain that was causing them to break, and he telegraphed instructions back to Cooper. The cables were adjusted accordingly, and the danger passed. This incident was prophetic of a similar one thirty-five years later, when Cooper’s career was at its zenith. However, in that case, the absentee chief engineer would not be so fortunate in getting his telegram through to his assistant.
After the Eads Bridge was completed, Cooper moved about for a while, in a manner not unfamiliar to engineers today. He served as superintendent of the shops for the Delaware Bridge Company, in Phillipsburg, New Jersey; worked as assistant general manager of the Keystone Bridge Company, in Pittsburgh; designed and built (i.e., oversaw the building of) the Laredo Shops of the Mexican National Railroad; remodeled and rebuilt the furnace plant of the Lackawanna Coal and Iron Company, in Scranton, Pennsylvania; and designed and built the Norton Cement Mills at Binnewater, New York. He was approved for hiring as an assistant to Wilhelm Hildenbrand, who had made the first drawings of the Brooklyn Bridge under the direction of John Roebling and who served as principal assistant engineer of the construction of the bridge under Washington Roebling, but it is not clear how extensively Cooper worked on that project. Nevertheless, with his broad and varied experience, he was able to establish himself as a consulting engineer in New York City in 1879.
The year 1879 is among the most infamous in the history of modern bridge building, for it was on the last Sunday of that year, December 28, that the Tay Bridge disaster occurred, an event that immediately affected the character of bridge design and construction endeavors throughout the world, was to affect Cooper in the twilight of his career, and to this day influences the way bridges are built and look. As with all bridges, the history of the Tay begins long before its name became familiar, even to engineers, and the nature of the bridge itself, or its influence on subsequent bridges, cannot be completely understood without understanding the circumstances surrounding its origins, design, and construction.
In the 1850s, travel to the east coast of Scotland above Edinburgh was a grueling ordeal. Although the town of Dundee was only forty-six miles north of Edinburgh as the crow flies, even in the best of weather a railroad journey took over three hours, because there were two wide and unbridged estuaries to cross. Passengers who left Edinburgh on the 6:25 a.m. to Grafton had to change there to a paddlewheel steam ferry, which carried them across the Firth of Forth to Burntisland; here they boarded a train that took them through Fifeshire to Tayport, then disembarked and boarded another ferry to carry them across the Firth of Tay to Broughty Ferry, where they finally caught a train that took them to Dundee. This was largely the route of the North British Railway—a successful line in the south, but one that was fast losing business in Scotland to the Caledonian Railway. The Caledonian route to Dundee was a much more comfortable journey, albeit a longer one, taking passengers well westward out of their way, through towns like Stirling and Perth, where the two firths had narrowed to rivers and were more readily bridged.
The word “firth” means “estuary” and is related to the old Norse word “fjord.” Unlike the Scandinavian arms to the sea, however, the Scottish firths are located not so much between steep cliffs as between gentle hills. This made ferry landings rather easily established, and would have made bridges and their approaches relatively uncomplicated, if the firths were not so wide near Edinburgh and Dundee. It may hardly have crossed the minds of railway directors and shareholders in the middle of the nineteenth century that bridges could be thrown across such great stretches of water, no matter how shallow these might be, and they accepted the limitations of “floating railways,” in which railroad cars fully loaded with coal or other commodities would be uncoupled at the water’s edge and rolled onto ferries, to be carried across the firth and then coupled to new locomotives for the continuation of the journey.
Thomas Bouch, who devised the scheme of the railway ferries, was born to a sea captain and his wife in Cumberland in 1822. At the age of seventeen, young Bouch became associated with the famous Stockton & Darlington Railway, designed and constructed by the engineer George Stephenson, whose portrait now appears on the English five-pound note. Railroads had been used for some time to move loads of coal and other heavy materials between mines, forges, shipping points, and the like, often in small hand-pushed or horse-drawn cars. When steam locomotives came to be used, it was clear that railroads could also serve to transport goods and people between towns. The Stockton & Darlington was among the first railways authorized by Parliament to be operated also for public transport, and September 27, 1825, when the first ticket was sold on the line, is often taken as the birthdate of the railways as we know them—true competitors of canals and carriage roads.
East coast of Scotland, showing railway connections around the Firth of Forth and the Firth of Tay, circa 1890 (photo credit 3.2)
In 1849, when he was twenty-seven, Bouch went to Scotland to become traffic manager and engineer of the Edinburgh & Northern Railway. He went on to design railway viaducts in the highlands, a tramway system for Edinburgh, and the railway ferries across the firths of Forth and Tay. When the Edinburgh & Northern was taken over by the North British Railway in 1854, Bouch proposed to the directors a bridge across the Firth of Tay, but some considered a two-mile-long structure “the most insane idea that could ever be propounded.” Opposition to the idea of a bridge at Dundee was not so much ridiculed as feared, however, in the town of Perth, about twenty miles up the Tay, where shipping interests worried about a bridge downstream blocking their access to the sea and their livelihood on the interior railroad. And one naysayer presciently articulated the fears of many along the wide, cold, and windy estuary: “The tremendous impetus of the icy blast must wrench off the girders as if they were a spider’s web, or hurl the whole erection before it.” In the final analysis, the long struggle between the Caledonian and North British railways for the Scottish traffic was the deciding factor.
It is said that the first time Bouch looked across the firths of Forth and Tay, he was convinced that they could be bridged, and subsequently spent his energies trying to convince others. The economic value in opening up a continuous rail link along the eastern Scottish coast was evident to all, and the final decision turned on the uncertain balance between projected cost and potential benefit. According to one account, at least, Bouch was driven by more than economics:
[T]he simple reason for his enthusiasm was that he was a dreamer, and the most determined type of dreamer who must build what he dreams. Perhaps in the darkness at night he already believed it built, and could have put out his hand from the sheets and touched its cold iron and masonry. All creative work has its greatest reality while it is still in a man’s mind, before he begins to execute it.
In July 1870, “after some twenty years of hawking his dream,” Bouch learned that royal assent had been given to the bill authorizing what was effectively a North British undertaking to bridge the Tay, and one year later he watched the laying of a cornerstone. The bridge was to consist principally of latticed girder or truss spans not unlike those that engineers like Simeon Post had only a few years earlier proposed to cross the Mississippi River at St. Louis. At Dundee, however, the Tay was over a mile wide, and since the combined railroad and firth alignments necessitated an oblique crossing with a wide turn at the northern bank, the Dundee side, the full length of the bridge over water was about two miles. Because of its width, however, the waterway was generally no deeper than about fifty feet, and no more than twenty feet of sand and gravel was believed to cover bedrock.
Until bridges are actually financed and begun, there usually remains a degree of uncertainty about the real conditions upon which physical foundations must rest, for there is seldom enough money to explore every square foot of bottom for a bridge that is as yet only some engineer’s dream. In the case of the Tay, excavation was to take place within large cylindrical caissons. Unlike those of the St. Louis Bridge, these caissons were not pressurized with air, and workers protected only by diving bells prepared the bottom for the construction of heavy brick piers. Once work was begun, however, it was soon evident that the riverbed conditions were not so substantial as test borings had indicated, and Bouch redesigned the piers to consist of groups of cast-iron columns on a wider base. This reduced the pressure on the sandy bottom to less than half of what was originally intended. The girders for the superstructure were fabricated near the shore, floated next to piers, and jacked into place. After about six years of work, in September 1877, the first train passed over the bridge.
The Tay Bridge consisted of eighty-five individual spans, the eleven greatest of which were 245 feet in length and known as the “high girders,” so designed to allow trains to pass through rather than over, and thereby to offer the least impediment to shipping. While no one of its girders was anywhere near record length, the Tay Bridge was overall the longest bridge in the world by far when it opened officially on June 1, 1878. A year later, Queen Victoria crossed the bridge and knighted Bouch for his accomplishment. A half year after that, during a fierce storm, the high girders of the bridge fell or were blown into the Tay, carrying with them the evening train from Edinburgh to Dundee and all of its seventy-five passengers. There were no survivors.
Though Bouch maintained that the “capsizing” of some of the cars of the train off the track and into the sides of the high girders brought them down, a court of inquiry discovered major flaws in the design and construction of the Tay Bridge. It was found, for example, that Bouch had grossly underestimated the effect of the strong winds that could develop along the firth. Upon being questioned about this during the inquiry, he gave no sign of having reconsidered the issue:
The Tay Bridge after the collapse of its high girders, on December 28, 1879 (photo credit 3.3)
Q: Sir Thomas, did you in designing this bridge, make any allowance at all for wind pressure?
A: Not specially
Q: You made no allowance?
A: Not specially.
Q: Was there not a particular pressure had in view by you at the time you made the design?
A: I had the report of the Forth Bridge.
The Forth was, of course, the other firth that had to be crossed by a bridge, and early in his design considerations Bouch had learned indirectly from Astronomer Royal Sir George Airy how great a wind force might be expected to push against each square foot of bridge area that might be thrown across the Firth of Forth. Airy, writing from the Greenwich Observatory, acknowledged that “for very limited surfaces, and for very limited times, the pressure of the wind does amount to sometimes 40 lb. per square foot, or in Scotland to probably more.” He suggested that, on average, the entire bridge would experience a pressure of ten pounds per square foot, which led Bouch to believe he could for all practical purposes ignore the effects of the wind on any firth, even though French and American engineers of the time were assuming wind forces five times Airy’s average amount and accordingly designing bracing and connections to resist them. The Tay inquiry concluded that “the fall of the bridge was occasioned by the insufficiency of the cross bracing and its fastenings to sustain the force of the gale.”
In addition to the inadequacy of the superstructure of the Tay Bridge to resist the wind, its piers were found to have been poorly constructed. After the accident, the iron was discovered to have been badly cast. It had tapered boltholes, resulting in loose connections; it had uneven thicknesses, causing unintended variations in strength; and it had large voids left by cast-in air pockets that were subsequently filled in at the Wormit Foundry with mixtures known there as Beaumont Egg, consisting of “beeswax, fiddler’s rosin, and the finest iron borings melted up, and a little lamp black.” The filler material was smoothed down and painted over—resulting, of course, in weak spots that were merely cosmetically sound.
As authorized by the Regulation of Railways Act of 1871, the Board of Trade had appointed a court of inquiry comprising three members: William Henry Barlow, president of the Institution of Civil Engineers; Colonel William Yolland, chief inspector of railways; and Henry Cadogan Rothery, wreck commissioner. Only the first two were engineers, and professional loyalties appear to have surfaced when the time came to draft the final report “upon the circumstances attending the fall of a portion of the Tay Bridge.” Though there seemed to be no substantial disagreement as to contributing factors to the failure, the two engineers could only conclude that they had “no absolute knowledge of the mode in which the structure broke down,” and hence were reluctant to place blame too squarely and explicitly on Thomas Bouch. Rothery, on the other hand, had no such uncertainty, and he chose to write a separate report. (The official report, which was issued in June 1880 and circulated “to both Houses of Parliament by Command of Her Majesty,” consisted of both views.) Rothery felt it was his duty to call it as he saw it:
We find that the bridge was badly designed, badly constructed and badly maintained and that its downfall was due to inherent defects in the structure which must sooner or later have brought it down. For these defects both in the design, the construction, and the maintenance, Sir Thomas Bouch is, in our opinion, mainly to blame. For the faults of design he is entirely responsible. For those of construction he is principally to blame in not having exercised that supervision over the work, which would have enabled him to detect and apply a remedy to them. And for the faults of maintenance he is also principally, if not entirely, to blame in having neglected to maintain such an inspection over the structure, as its character imperatively demanded.
Sir Thomas went into seclusion and died four months later, at fifty-eight. He would be remembered in history not for his legacy of three hundred miles of railway functioning properly in England and Scotland but for the failure of his Tay Bridge. Not only a successful bridge across the Tay, but also one across the Firth of Forth were the legacies Bouch must have dreamed about. Indeed, his design for a bridge across the deeper Firth of Forth had been under construction for over a year when the Tay fell. Bouch’s scheme for a suspension bridge of two great spans of sixteen hundred feet each might have resulted in an accomplishment that would have overshadowed the Brooklyn Bridge, then under construction in New York. With the disaster at the Tay, however, work at the Firth of Forth was suspended, and there was a general loss of confidence in the project, especially when it came out that Bouch had designed his bridges, on average, for only ten pounds of wind pressure. Even then, Bouch’s design was not formally abandoned by the Railway Board until a full year after the Tay disaster, and six months after the court of inquiry’s report, in part because there was still a great desire for bridges across the Scottish firths.
The Tay Bridge had, after all, operated successfully for more than a year, and it had demonstrated the great economic value of bridges across the firths. It should not be surprising, then, that a new Tay Bridge, which would have two tracks rather than one and would accordingly be wider and more substantial, was soon proposed. Less than eighteen months after the first Tay Bridge collapsed, plans for a new one were submitted for parliamentary approval, which was required for all civil-engineering works. The new undertaking was overseen by the firm of Barlow, Son & Baker, and the engineer was to be William H. Barlow himself, with his son, Crawford Barlow, as his assistant. The second Tay Bridge was to be constructed sixty feet upstream from the first, with piers spaced the same distance apart so that the sound girders, which did not fall, could be easily reused. The high girders were redesigned to much more substantial standards than Bouch’s, including the ability to resist a wind pressure of fifty-six pounds on every square foot, and all cylinders of the supporting piers were to be tested well beyond the load they were expected to carry. There was naturally great local interest in the design of the replacement structure, and the piers of the “New Viaduct” and the “Old Bridge” were contrasted in the October 18, 1881, issue of the Dundee Advertiser as follows:
The massive character of the new structure as compared with the old is obvious at a glance, especially (1) the greater lateral stability from the substitution of twin piers for the single pier below, and the increased width for the double line of rails above; and (2) the greater vertical stability from the diminished height of the superstructure and the arched formation at the upper junction of the piers.
As in the wake of all major failures, the design of the new structure had improved features that far exceeded correcting the deficiencies of the old. With favorable public opinion thus assured, tenders were invited, and that of William Arrol & Company of Glasgow was accepted late in 1881. Construction began the next year and was completed in 1887. The stumps of the original bridge piers remain in place today, serving as tidal breakwaters for the much more substantial piers of the second Tay Bridge, and as a stark reminder of the accident and its victims.
When the time came, in 1881, to have a new bridge designed for the Firth of Forth, proposals were invited by the Railway Board from its consulting engineers, Sir John Fowler, William Barlow, and Thomas E. Harrison, who had been set up as a panel to reexamine Bouch’s scheme. John Fowler, then approaching sixty-five years of age, was younger by almost five years than Barlow and by almost ten years than Harrison. Fowler had begun his training as a civil engineer at sixteen, given evidence before Parliament by the time he was twenty-one, and been in charge of a railway-construction project at twenty-two. In his mid-forties, he had been involved in seventy to eighty “major schemes” a year, and it has been estimated that he must have been involved in over a thousand jobs over the course of a professional career that spanned more than sixty years, working with at least fifty different assistants. Talented assistant engineers were clearly essential to someone like Fowler, and his assistant on the Firth of Forth project, Benjamin Baker, was among the best. Baker, thirty years Fowler’s junior, began work in his London office on the Metropolitan Railway project, the first link in the London underground when it opened in 1863, but preferred designing long-span bridges.
The high girders of the rebuilt Tay Bridge, as they stand today, with the stumps of the original bridge still visible in the water (photo credit 3.4)
A truss- or girder-bridge design was not appropriate for the Firth of Forth, because the many piers that would have had to be sunk in deeper water would have presented an engineering challenge and an unwanted expense. Besides, it was a girder bridge across the Tay that had failed, so adverse public opinion would have had to be overcome. Suspension bridges had long been suspect in Britain for rail traffic, but John Roebling’s successful one over the Niagara Gorge had put the form in a new light. However, the problems with wind, and the fact that the now abandoned design of Bouch had been of the suspension type, again cast it in disfavor. Fowler and Baker were thus inclined, for both technical and nontechnical reasons, to look to different bridge forms entirely.
The location that Bouch had identified was ideal, in that the firth was relatively narrow there, albeit relatively deep, and in that about midway between the shores, at Queensferry and South Queensferry, was an island, or “garvie” in Scots. It was said to be named Inchgarvie because its representation on a scale map was an inch long; coincidentally, its shape also resembled that of a small herringlike fish called a garvie. According to the engineer Baker, who later lectured on the design of the bridge, the area “should be well enough known to every reader of fiction,” for it was the setting of Robert Louis Stevenson’s Kidnapped, whose hero was taken “at the very spot where the bridge crosses.” However, what presented themselves here to Baker and Fowler were not fictional settings but physical conditions for a bridge with piers only on the island and on or near the shores, which thus required two free spans each on the order of seventeen hundred feet. No such bridge had ever been built anywhere in the world.
What was being constructed in recent years in Europe and America, however, was a somewhat new type of bridge that was being used to span increasingly greater distances with as few supports in the water as possible. One of the earliest of these bridges was completed in 1869 over the River Main at Hassfurt, Germany, by the Bavarian engineer Heinrich Gerber, who a few years earlier had been granted a patent for the design, which came to be known as a Gerber bridge. In his bridge, which looked not unlike the high dark bridge that today carries the Pulaski Skyway over New Jersey marshland, the girder depth varied along the length of the bridge, which was articulated at strategic locations in order to simplify design calculations and to allow for minor settlement of the piers without exerting undue stress on the superstructure.
Gerber’s concept had considerable appeal to engineers, and many other “Gerber bridges” were built according to similar principles, in part because bridge engineering generally had evolved to the point where this bridge type was a natural solution for supporting the increasingly heavy loads of commerce. Thomas Bouch had, in fact, designed and built one of the first such bridges in England in 1871, at Newcastle. This was apparently forgotten when the Tay disaster occurred; otherwise Bouch’s involvement might have given this genre a bad name as well, at least among the general public and politicians.
In America, the expanding railroads presented many opportunities to build new bridges, and by 1877 a Gerber-type bridge with three 375-foot spans was carrying the Cincinnati Southern Railway over the Kentucky River. The engineers of this bridge were Louis G. F. Bouscaren, who had been an assistant engineer on the Eads Bridge, and Charles Shaler Smith, who was responsible for the Illinois approach to that bridge. Shaler Smith was born in Pittsburgh in 1836 and was to die in St. Louis fifty years later. As a child, he attended private school, but he apparently had no formal engineering training. Nevertheless, his work with Gerber-type bridges was instrumental in introducing the form to America, and his writings on comparative analyses of different truss types and on wind pressure on bridges were important contributions to bridge design in America.
In 1883, as construction was beginning on the Firth of Forth bridge, a Gerber-type with a 495-foot span was completed, built for the Michigan Central and Canada Southern railways. It was almost 240 feet above the Niagara Gorge and just south of Roebling’s suspension bridge, also known as the Grand Trunk Bridge. The chief engineer was Charles Conrad Schneider, born in 1843 in Saxony, where he was trained and practiced as a mechanical engineer before coming to America in 1867. He began work here, as many immigrant engineers then did, as a draftsman. His early work with the Rogers Locomotive Works in Paterson, New Jersey, led to his involvement with railroad companies, and before long he was in charge of engineers in the New York office of the Erie Railroad, whose chief engineer was Octave Chanute. Born in Paris in 1832, Chanute moved to America with his family when he was eight years old, attended private schools in New York, became an assistant chainman on the Hudson River Railroad while still a teenager, and worked his way up the railroad ladder. In the process, he had gained enough experience in matters of the maintenance of ways to become involved in extending existing railroads. From 1867 to 1869, Chanute designed and oversaw construction of the first bridge over the Missouri River, at Kansas City. Later in life, he became interested in the nascent field of aviation, which led ultimately to the association of his name with an air-force base in Illinois.
In Chanute’s office, Schneider had the responsibility for checking the bridge plans submitted by bridge companies, a practice not generally carried out by railroads at that time. In particular, Schneider was responsible for checking the strain sheets, which showed the portion of the load that each member of a bridge was designed to carry. It was a natural development for bridges also to come to be designed in railroad offices. Once designs became specified by the railroad, rather than as part of a lump-sum contract that included everything from design to construction by a bridge-building company, the Erie Railroad began to buy its bridges by weight, for the price of materials was the chief determinant of cost. The practice of letting bridge contracts by the pound soon became widespread.
John Roebling’s Suspension Bridge and the cantilever bridge over the Niagara Gorge, with Whirlpool Rapids in the foreground, in an etching from one of the many late-nineteenth-century tour guides of the area (photo credit 3.5)
The invitation to the opening of the bridge below Niagara Falls was signed by Chanute’s protégé, Schneider, as chief engineer of the project. The engraving on the invitation shows Schneider’s bridge in the foreground and the famous suspension bridge in the background—symbolic and prophetic of the relative positions the two bridge types were to hold, in the minds of some at least, for the next three decades or so. Also indicative of the climate in which bridge building was taking place in the closing decades of the nineteenth century, the 1883 invitation associated no personal name with the great structure, which was called simply, directly, and technically the “Canti-lever Bridge below Niagara Falls.”
The hyphenation of the word “canti-lever” attests to how newly coined it was, at least with reference to bridge building; it required explanation, especially when applied to Fowler and Baker’s bridge, under construction across the Firth of Forth, less than fifty miles south of where the Tay Bridge had collapsed. Though Eads had in fact begun his explanation of the principle of his arch bridge with a discussion of a canted lever, that fifteen-year-old report to the Illinois and St. Louis Bridge Company had been generally forgotten. In fact, the cantilevered method of construction used in erecting the Eads Bridge, once the most striking visible feature of the project, was now seldom referred to.
With the growing publicity in both Britain and America surrounding the supposedly new type of bridge, the hyphen was quickly dropped—but not the curiosity about the form. A reader of Engineering News, who wrote to the editor in late 1887 from an engineer’s camp near Danielsville, Georgia, asked, “Whence comes the term ‘Cantilever’ as applied to bridges; or in other words what is a Cantilever bridge?” The editor responded:
This is a question quite frequently asked and we might as well answer once for all. The term, as applied to a bridge, is of comparatively recent origin, but the principle is as old as the Hindoos and the art of building itself. It has been applied to wooden bridges for centuries, and it is only its later scientific solution by modern builders of steel and iron bridges that has brought it forward again prominently. Its advantage over other forms of truss construction is, that by a proper method of anchoring or balancing and the arrangement of its tension and compression members, it can be erected over space without supporting false-work. The Niagara and the Forth bridges are the latest examples of its application to a site where the conditions made false works impossible, or very expensive.
The idea of a cantilever played a central role in a remarkable lecture that Baker delivered at the Royal Institution in 1887, in which he also gave some indication of the public scrutiny under which the new bridge was being built. Eight years after the Tay Bridge disaster at Dundee, he felt it necessary to preface his remarks with a declaration that the Forth and Tay bridges were quite different structures, albeit still confused in the public’s mind. He related an exchange he fully expected to have with every second Britisher: “ ‘How are you getting on with the Tay bridge?’ I suggest ‘Forth Bridge,’ and the correction is generally accepted as a mere refinement of accuracy on my part.” Not surprisingly, Americans were no more sure about Scottish geography. A report in Scientific American in early 1888 on the progress of construction on the cantilever bridge at Poughkeepsie, New York, misidentified the setting of the Forth cantilever as “between England and Scotland.”
It was not just the location of the bridge that Baker was at pains to explain; he had also to convey a sense of its great size, each span being almost four times as long as the longest tubes in Stephenson’s famous Britannia Bridge. Baker appealed to common points of reference to enable his London audience to appreciate the size of the Forth’s spans:
To get an idea of their magnitude stand in Piccadilly and look towards Buckingham Palace, and then consider that we have to span the entire distance across the Green Park, with a complicated steel structure weighing 15,000 tons, and to erect the same without the possibility of any intermediate pier or support. Consider also that our rail level will be as high above the sea as the top of the dome of the Albert Hall is above street level, and that the structure of our bridge will soar 200 ft. yet above that level, or as high as the top of St. Paul’s. The bridge would be a startling object indeed in a London landscape.
Benjamin Baker, circa 1890 (photo credit 3.6)
The image of the bridge amid familiar projections into the London skyline, as well as transported landmarks such as the Great Pyramid at Giza, St. Peter’s in Rome, the Cathedral at Chartres, and a host of others, was to be made real in a mural in the South Kensington Museum. But Baker wished to convey to his audience not only the monumental size of his bridge but also the principles by which it stood. He asserted that it had “excited so much general interest” in part because it was “of a previously little known type.” He would “not say novel, for there is nothing new under the sun,” but made no references to Gerber’s bridge, the American examples, or the cantilever method of construction of the Eads Bridge.
Baker did acknowledge that a visitor being shown about the construction site had suggested a Chinese precedent, to which the engineer replied, “Certainly.” He went on to elaborate:
The Forth Bridge drawn to scale before familiar structures and landmarks (photo credit 3.7)
Indeed, I have evidence that even savages when bridging in primitive style a stream of more than ordinary width, have been driven to the adoption of the cantilever and central girder system, as we were driven to it at the Forth. They would find the two cantilevers in the projecting branches of a couple of trees on opposite sides of the river, and they would lash by grass ropes a central piece to the ends of their cantilevers and so form a bridge. This is no imagination, as I have actual sketches of such bridges taken by exploring parties of engineers on the Canadian Pacific and other railways, and in an old book in the British Museum, I found an engraving of a most interesting bridge in Thibet upwards of 100 ft. in span, built between two and three centuries ago and in every respect identical in principle with the Forth Bridge. When I published my first article on the proposed Forth Bridge some four years ago, I protested against its being stigmatised as a new and untried type of construction, and claimed that it probably had a longer and more respectable ancestry even than the arch.
Baker seemed willing to acknowledge the ancient roots of his bridge, but nowhere in his lecture did he emphasize the precedents of his near contemporaries, Gerber, Shaler Smith, or Schneider. Indeed, after establishing the time of his first publication on the topic, Baker made remarks that cause the modern reader to wonder whether he read nothing but old books or simply did not wish to acknowledge the competition. Charles Schneider’s fifty-page article on a cantilever bridge at Niagara Falls, followed by even more pages of discussion, had appeared in the Transactions of the American Society of Civil Engineers two years before Baker’s lecture. However, at the time, British engineers generally seemed little interested in recognizing or acknowledging American precedents. In a passage remarkably reminiscent of Eads’s feud with Roebling in the pages of Engineering, Baker continued:
An Asian cantilever bridge with a central girder span, which Baker found identical in principle to the Forth Bridge (photo credit 3.8)
The best evidence of approval is imitation, and I am pleased to be able to tell you that since the first publication of the design for the Forth Bridge, practically every big bridge throughout the world has been built on the principle of that design, and many others are in progress.
Interestingly, Baker avoided the use of the term “cantilever” in this passage, perhaps to make his assertions literally correct. Earlier in his lecture, however, he had introduced the new term with some elaboration, and reservation as to whether his bridge was a true cantilever:
One of the first questions asked by the generality of visitors at the Forth is—why do you call it a cantilever? I admit that it is not a satisfactory name and that it only expresses half the truth, but it is not easy to find a short and satisfactory name for the type. A cantilever is simply another name for a bracket, but a reference to the diagram will show that the 1700 ft. openings of the Forth are spanned by a compound structure consisting of two brackets or cantilevers and one central girder.
The anthropomorphic model that Baker used in his lectures on the Forth Bridge (photo credit 3.9)
Baker then described how, in preparing for his lecture, he “had to consider how best to make a general audience appreciate the true nature and direction of the stresses on the Forth Bridge, and after consultation with some engineers on the spot, a living model was arranged.” The elusive Baker did not make clear whether he, the engineers, or all together came up with the idea, but the striking anthropomorphic model was very effective and often reproduced, both literally and visually, at the time:
Two men sitting on chairs extended their arms and supported the same by grasping sticks butting against the chairs. This represented the two double cantilevers. The central girder was represented by a short stick slung from one arm of each man and the anchorages by ropes extending from the other arms to a couple of piles of brick. When stresses are brought on this system by a load on the central girder, the men’s arms and the anchorage ropes come into tension and the sticks and chair legs into compression. In the Forth Bridge you have to imagine the chairs placed a third of a mile apart and the men’s heads to be 300 ft. above the ground. Their arms are represented by huge steel lattice members, and the sticks or props by steel tubes 12 ft. in diameter and 1¼ in. thick.
Nor did Baker mention who represented the “load on the central girder” in the human model. In fact, it was Kaichi Watanabe, a young Japanese engineer, apparently among the first from his country to study in Britain, who was sitting, hands to his sides, grasping what looks like a very narrow swing-like seat representing the central span of the bridge. He was a student of Fowler and Baker and “was invited to participate in the human model of the cantilever to remind audiences of the debt the designers owed to the Far East where the cantilever principle was invented.” In fact, New York’s Engineering News actually reproduced the “ingenious illustration of the cantilever bridge principle” a full six weeks before it appeared in London’s Engineering and called the model “a Japanese idea, as may be suspected from the central figure,” Watanabe. The American journal also reported that the model was “received with loud and general applause” during Baker’s lecture.
The report in Engineering News was no anomaly, for in America there was considerable interest in the design and construction of the Forth Bridge and large and unique engineering projects generally, even if their American precedents were not acknowledged. Engineers and information could and did travel freely and relatively quickly by ship across the ocean, as Eads and Roebling knew, and the transatlantic cable had been operational for two decades. In the case of the human model of the Forth Bridge, Engineering News acknowledged its indebtedness to Thomas C. Clarke, a former director and future president of the American Society of Civil Engineers, for the use of the original photograph from which the illustration could be reproduced only weeks after Baker’s speech. This makes Baker’s silence about the existence of not insignificant contemporary cantilever bridges in America all the more inexcusable, and it reinforces the judgment that he at least, if not the entire British engineering profession, was unwilling to acknowledge that there was much to be learned from contemporaneous American experience. If anything, Baker offered a bit of gratuitous ridicule of the eighteen-hundred-foot cantilever bridge that the American Thomas Pope had proposed in 1810 to join New York and Brooklyn. He called his bridge a “flying lever pendant” and, reminiscent of a more famous Pope, described it in heroic couplets. Baker quoted from these in his lecture, no doubt because they gave so apt a description of his own project:
Two of many possible ways proposed to bridge the Firth of Forth, with the accepted design below (photo credit 3.10)
Each semi-arc is built from off the top,
Without the aid of scaffold, pier, or prop;
By skids and cranes each part is lowered down,
And on the timber’s end grain rests so sound.
Sure all the bridges that were ever built,
Reposed their weight on centre, pier, or stilt;
Not so the bridge the author has to boast.
His plan is sure to save such needless cost.…
Baker admitted approvingly that, should he have thought of describing his own bridge in verse, he would have “appropriated bodily Mr. Pope’s lyrical version.” However, Baker chose “sober prose” to describe the Forth Bridge, which after all was soon to be a completed reality rather than the unrealized dream of an American poetaster.
Construction of the Forth Bridge began, as did that on the Eads and Brooklyn spans, with the sinking of caissons, and Baker again avoided mentioning the singular achievements of those recently completed American bridges except to note that almost one out of every five men who worked on the foundations of the St. Louis Bridge was attacked by some form of caisson disease, with sixteen deaths, whereas his bridge had “no deaths directly attributable to the air pressure.” There were accidents, of course, especially among workers assembling the superstructure. Baker closed his speech by speaking of the risk that the “zealous and plucky workmen” performed high above the firth. Speaking on behalf of the engineers, he said, “we never ask a workman to do a thing which we are not prepared to do ourselves, but of course men will, on their own initiative, occasionally do rash things.” He concluded, rather insensitively:
Happily there is no lack of pluck among British workers; if one man falls another steps into his place. Difficulties and accidents necessarily occur, but like a disciplined regiment in action we close up the ranks, push on, and step by step we intend to carry on the work to a victorious conclusion.
The Forth Bridge under construction (photo credit 3.11)
Construction of the Forth Bridge was under the personal direction of the contractor William Arrol, whose company built the second Tay, but here he was in partnership with Joseph Phillips, who had considerable experience building large bridges, and with Sir Thomas Tancred and Travers H. Falkiner. Work was concluded in 1890, and early that year the definitive and comprehensive account of the project was written by Wilhelm Westhofen, the engineer who had supervised the building of the central section. Among the “chief desiderata,” according to Westhofen, was the need for the “maximum attainable amount of rigidity,” not only vertically, under railroad trains, but also horizontally, against wind pressure, so that the completed bridge “may by its freedom from vibration gain the confidence of the public, and enjoy the reputation of being not only the biggest and strongest, but also the stiffest bridge in the world.” This was necessary, of course, because the memory of the decade-old Tay disaster was still fresh. It might not have been necessary, however, for Westhofen to remind his readers that Bouch’s “original suspension-bridge design complied with none” of the desiderata, which also included assurances of fully tested materials, facility of erection (during which time the incomplete bridge was expected to be as safe against the wind as the completed structure was to be), and maximum economy consistent with safety.
The Eads Bridge is generally acknowledged as the first to use steel, and its success may have led to the Board of Trade’s 1877 lifting of its ban on the use of steel in British bridges. The Forth was thus the first major bridge to be made fully of steel, which was manufactured using the Siemens-Martin open-hearth process. The bulk of the material was supplied by the Steel Company of Scotland, with some also coming from Wales. The Clyde Rivet Company in Glasgow supplied the forty-two hundred tons of rivets required. Although steel was 50 percent stronger than wrought iron, Baker assured his audience at the Royal Institution that the material used in the bridge was “not in any sense of the word brittle, as steel is often popularly supposed to be, but it is tough and ductile as copper.” He went on to make the point in more familiar terms: “You can fold ½ in. plates like newspapers, and tie rivet bars like twine into knots. The steel shavings planed off form such long, true and flexible spirals, that they are largely used for ladies’ bracelets when fitted with clasps and electro plated.”
The completed Forth Bridge, showing Inchgarvie under the central pier and the South Queensferry landing (photo credit 3.12)
For all the flexibility of the steel shavings, the bridge certainly was stiff—even during construction, when its great cantilever arms grew out symmetrically from each pier. It looked not unlike the Eads Bridge during its construction, but whereas the towers and cables that held up the Eads could be removed once the arches were complete, there would be no such extraneous falsework to be removed once the Forth Bridge was completed. Only the riveting cages and cranes would have to be taken off the finished bridge. Baker had predicted that each 1,710-foot span would deflect no more than four inches under the heaviest train, and measurements on the finished bridge showed an actual deflection of only three and a half inches.
The bridge was built “straddle legged” not only to achieve a great stiffness against the wind but also to look as if it did. The columns over the piers are as much as 120 feet apart at the base but only thirty-three feet apart at the top, giving the bridge the appearance of being able to withstand the severest blow. The bridge has been referred to as having a “Holbein straddle,” after the stance that characterized male portraits by the German artist Hans Holbein. Fowler was apparently quite aware of this, reportedly having once remarked to the Scottish-born mechanical engineer James Nasmyth, at a London exhibition of Holbein’s work, that the Tay might not have fallen had its piers had such a straddle.
The question of the aesthetic qualities of cantilever bridges in general and the Forth Bridge in particular was a much-discussed subject in the late 1880s. In a letter to Engineering News, F. J. Amweg, a civil engineer from Philadelphia, admitted that “the ‘cantilever fever’ is prevalent at the present time.” However, he defended the design of his city’s Market Street Bridge, in response to an article by the Pittsburgh engineer Gustav Lindenthal, who alluded to the bridge as just “another ugly looking cantilever bridge.” Such an aversion to the form foreshadowed the career of Lindenthal, who was to play a dominant role in late-nineteenth- and early-twentieth-century American bridge building, but that is a topic for the next chapter.
In another of his many lectures on the Forth Bridge—this one in 1889, before the Library Institution of Edinburgh—Baker contended that the beauty or ugliness of the bridge had to be considered in the context of its size. He was reported to have said that “it was useless to criticise the design on paper, because the mental emotion arising from its enormous size was absent.” His remarks were in response, at least in part, to growing criticism from the likes of William Morris, who had recently said that “there would never be an architecture in iron, every improvement in machinery being uglier and uglier until they reach that supremest specimen of ugliness—the Forth Bridge.” Baker argued in his lecture that it was not possible to judge an object’s beauty without knowing the functions it was designed to satisfy. Though the marble columns of the Parthenon were beautiful in their place, for example, they would cease to be so if bored through and used as funnels for an Atlantic steamship; he admitted, however, that, “of course, Mr. Morris may think otherwise.” Baker stated that he and Fowler had indeed considered aesthetics in their design.
Other critics of the Forth Bridge faulted it for its structural excess and its consequent great cost. Not the least among these critics was Theodore Cooper, who shortly after the great Scottish bridge was finished would make comments upon it that years later would come back to haunt him:
You all know about the Firth of Forth bridge, the clumsiest structure ever designed by man, the most awkward piece of engineering in my opinion that was ever constructed, from the American point of view. An American would have taken that bridge with the amount of money that was appropriated and would have turned back 50 [percent] to the owners, instead of collecting when the bridge was done, nearly 40 [percent] in excess of the estimate.
The Forth Bridge has continued to have its aesthetic and structural champions and detractors, which is not surprising considering the scale and unusualness of the structure. To give a sense of the bridge’s scale, Engineering published in 1889 a diagram that compared the size of the Forth Bridge with that of the Eiffel Tower, then recently completed in Paris. Two Eiffel Towers were drawn on their side, balancing each other foot to foot, with two equally large half-spans of the Forth Bridge superimposed. Not incidentally, this comparison with the tower widely known to have been designed to resist principally the force of the wind, could do little but reinforce the impression of a sturdy and safe bridge. However, neither this exhibition of scale or stance nor the human model demonstrating the structural principles involved, represented the bridge in full. Whereas the Eiffel Tower diagram showed only one pier and two half-spans, and whereas the human model showed two piers and their respective four half-spans, plus a suspended span, the actual Forth Bridge has three piers, six cantilever arms, and two suspended spans. Were the three towering column structures not such a dominant visual feature of the bridge, it might have been criticized as having an even number of full spans, something many bridge engineers believe makes for an inferior visual composition. However, in the Forth Bridge, the light suspended spans are not so much the focus of attention as are the heavy, straddling towers and their symmetrically cantilevered arms, so the bridge appears to bound across the firth in an odd number of leaps that works both visually and structurally.
The completed bridge was tested in January 1890, during a severe gale, with two trains, each comprising three seventy-three-ton locomotives pulling fifty cars full of coal, with another three locomotives bringing up the rear. The total weight on the bridge was eighteen hundred tons, under which the ends of the cantilevers deflected only about seven inches. Though the trains ran side by side on the two-track bridge, they were not allowed to cross it completely—that first full crossing would not occur until January 24, when it was achieved by a special passenger train carrying the chairmen of the railroad companies. The formal opening of the Forth Bridge occurred on March 4, when the Prince of Wales, accompanied by his son, Prince George, and the dukes of Edinburgh and Fife, rode across in a train and declared the bridge opened. In a ceremony on the occasion, the prince announced that knighthood had been conferred by Queen Victoria upon Benjamin Baker and William Arrol—Sir John Fowler had already been so honored—for their work on the Tay and Forth bridges, which signaled the progress that was being made in bridge building worldwide.
The cover of the souvenir program showed a North British Railway locomotive labeled “Progress” pulling a through passenger carriage labeled “Aberdeen to New York, via Tay Bridge, Forth Bridge, Channel Tunnel, and Alaska.” Dreams are always in advance of reality, however, and a Channel tunnel, the boring of which had in fact begun years before, would not be completed for more than a hundred years. Prior to the 1990 centennial of the Forth Bridge, it was given a thorough inspection and declared to be in fine shape, a result of its having been conscientiously maintained throughout its first hundred years; and it was predicted that “given reasonable care and maintenance [the bridge] will last for another 100 years.” Thus the Aberdeen–to-New York through train might still someday be achieved, for a trans-Siberian railway was officially completed in 1991, and a bridge connecting Siberia and Alaska across the Bering Strait was for some time the dream of such engineers as Joseph Strauss and Tung-Yen Lin. Though none of these would realize their dreams, that is not to say that their successors will not take the project up; but it will be one for another century.
While the Forth Bridge was being built in Scotland, American bridge construction was also continuing to advance. Octave Chanute had overseen the building of the two-thousand-foot-long, three-hundred-foot high Kinzua Viaduct, carrying the Erie Railroad’s new division into the mining region of northwestern Pennsylvania. Originally constructed out of wrought iron in 1882 by the Phoenix Bridge Company of Phoenixville, Pennsylvania, the structure would be replaced with a stronger steel design in 1900. (It now stands unused in Kinzua Bridge State Park.)
The Brooklyn Bridge was completed in 1883, under the supervision of Washington Roebling and his wife, Emily Warren. With a clear span of 1,595 feet between stone towers with Gothic arches, it was famous for being the longest suspension bridge in the world, but it was soon so congested with traffic that talk of other bridges across the East River began almost immediately upon its opening. Furthermore, the bridge, designed for the lighter trolley and road traffic of almost twenty years earlier, was not structurally able to carry heavy locomotives, and for years elaborate schemes of switching cable cars at the New York and Brooklyn terminals would be an almost constant topic of discussion in the pages of Engineering News.
The Kinzua Viaduct, as it looked in the late nineteenth century, in northwestern Pennsylvania (photo credit 3.13)
Expanding cities and railroads needed more and more bridges, and the steadily increasing volume and weight of traffic they were being required to carry made bridge design an ever-challenging endeavor, whose practitioners welcomed new and better ways of determining the loads that various kinds of vehicles and trains imposed on a structure. There is seldom a single method that is all things to all engineers, and different individuals at a given time often have different views of how best to design a bridge. In the late nineteenth century, a technical paper published in the Transactions of the American Society of Civil Engineers, which was a principal forum for such discussions, was often followed by at least as many pages of discussion by a dozen or more of the author’s prominent contemporaries (as had Schneider’s 1885 paper on the Niagara Falls cantilever). The pages of Engineering News and its successor, Engineering News-Record, also often contained exchanges between engineers, like those that had appeared in Engineering between Eads and Roebling over the design of caissons, but these tended to be more one-on-one serial debates and could be less dignified professionally.
The bulk of what the likes of James Eads and the Roeblings wrote about bridge design appeared in the form of reports to those from whom they wanted initial or continuing financing. They published relatively little about bridge building in professional journals; therefore, with a few notable exceptions, their theoretical outlook tended not to be so influential as their practical achievements in construction. Those engineers who wrote more constantly and openly about bridge design and construction tended to have a much more immediate influence on the nature of design as practiced within the profession. Having technical papers noticed and discussed in the Transactions of the American Society of Civil Engineers was a guarantee for gaining recognition among engineers, but an alternative way to disseminate one’s ideas and methods was book publication.
Theodore Cooper was a frequent contributor of papers to meetings and journals of the American Society of Civil Engineers, and he twice received that society’s prestigeous Norman Medal for his contributions. His 1880 medal-winning paper, “The Use of Steel for Railway Bridges,” showed him to be innovative, for no major bridge had yet been built entirely of the relatively new material. In the mid-1880s, he first published his book, General Specifications for Iron Railroad Bridges and Viaducts, which has been described as comprising “the first authoritative specifications on bridge construction that had been published and circulated.” The title soon expanded to include steel bridges. Cooper’s book was issued in its seventh edition in 1906.
Among the things that made Cooper’s name most well known among engineers was his system of accounting in the design process for the loads of railroad trains on a bridge structure. He represented the heaviest locomotive then known by means of the forces it exerted through its driving wheels, and represented the train it pulled as a single, uniformly distributed load related to those forces. This made it convenient to modify earlier bridge designs as locomotives and the cars they pulled became heavier, which they seemed constantly to do. Cooper’s system was widely adopted, and by the early twentieth century had become “the almost universal standard for railway bridge design in America.” As convenient as his method was for dealing with trains of increasing weight, Cooper also strongly advocated the more accurate method of representing the load of a train on a bridge by the individual loads transmitted through each wheel. He published tables that made it possible for design engineers to carry out such analyses rapidly and conveniently. All such refinements in calculation meant, of course, that railroad bridges could be designed more accurately, and therefore more economically. No undue iron or steel needed to be added because of uncertainties as to how the bridge might be loaded by a heavy train moving across it.
Cooper’s 1889 paper on American railroad bridges constituted a concise history, beginning with seventeenth-century wooden bridges and concluding with a section on the failure of bridges, then a matter of increasing concern to the railroads and their passengers. What the disaster of Tay Bridge was to Britain, the collapse of the Ashtabula Bridge almost three years to the day earlier, on December 29, 1876, had been, even more immediately, to American bridge building. The bridge had been erected in the mid-186os across a deep gorge at Ashtabula, Ohio, about fifty miles east of Cleveland on Lake Erie, on the Lake Shore & Michigan Southern Railroad. It was basically what is known as a Howe-type truss design, but with additional diagonals, and with cast iron replacing wooden members. The design had been modified by Amasa Stone. Born in Charlton, Massachusetts, in 1818, Stone began his career as a carpenter and, with his brother-in-law, William Howe, the inventor of the truss type, acquired a contract to build the first railroad bridge over the Connecticut River, in 1840, and with a partner, acquired patent rights to the Howe truss in 1842. He went on to a remarkable railroad career, which included being president of the Cleveland, Painesville & Ashtabula Railroad, which he had built, and which had merged with the Lake Shore & Michigan before the bridge collapsed. The 165-foot span was being crossed by a train of two locomotives pulling eleven railroad cars westbound at fifteen miles per hour, when the driver of the first locomotive felt the bridge sinking. He opened his throttle wide and got safely across, but the other locomotive and all the cars went down with the bridge. At the time, it was still snowing after a recent blizzard; eighty people died in the icy wreck.
According to some accounts, Stone had been warned by engineers that the structure would be unsafe, and it was generally assumed that the bridge was cheaply built. However, after the accident it was found that, at $75,000, the bridge had actually been relatively costly to build. The engineer responsible for inspecting the structure became so disturbed by the blame heaped upon him that he committed suicide. Although Stone and his design were eventually condemned by the American Society of Civil Engineers, the exact cause of the failure is still not known with absolute certainty. One possible explanation is that a car or cars became derailed, perhaps when the driver lurched his locomotive forward because he thought the bridge was falling, and the truss was so damaged by the impact of the wheels that it could no longer support the unusual load. Whatever the cause, increased attention was devoted to bridge building in America after 1876.
Cooper wrote, more than ten years after the Ashtabula accident, that it “not only alarmed the general public, but also shook the blind confidence of the railroad companies in their existing bridges,” and he outlined how the situation had changed in the meantime. Subsequent inspections of bridges and procedures uncovered weaknesses, not only in existing bridges but also in existing ways of designing and building them. Cooper was especially critical of designs that did not balance careful analysis with judgment about constructability. He documented how the loads that railroad trains exerted on longer bridges had about doubled from 1873 to 1889, and he called for more precise methods of analysis. In particular, Cooper advocated the adoption of his method based on locomotive wheel loadings, which he acknowledged had been “worked out independently but simultaneously by Mr. Robert Escobar, C.E., of the Union Bridge Company,” in 1880.
Cooper called attention to an 1878 publication of his own as being “the first paper on bridge construction in which that relic of ignorance, the ‘factor of safety,’ was entirely omitted.” He recognized that bridges should be built with a considerable measure of strength beyond that calculated, but he believed that safety should be based upon rational calculation coupled with careful material testing and inspection, rather than upon an arbitrary numerical multiplier. He opposed “stringent rules,” what today would be called codes of practice, that placed mandatory numerical requirements on such things as factors of safety. Good bridge building, he maintained, could not be based “merely upon a theory of stresses.” Rather, it “must provide for all those requirements of stability and solidity which are instinctively recognized by the practical engineer, and which cannot be complied with by merely using a large factor of safety.” Cooper could not have known at the time how ironic his own words would become.
Toward the end of his authoritative paper, Cooper summarized the benefits that had accrued from “the American system of competitive bridge construction,” which, according to him, involved aspects of evolution of truss designs, economy of details, and advances in theory absent from British practice. But Cooper also acknowledged some limitations of the competitive system, including “the American idea of building cheap railroads far in advance of the immediate demands of the regions through which they run, to settle those districts and build up a future paying traffic,” which “compelled the use of cheap and light bridge structures,” thus “favoring the lowest bidder.” He insisted, however, that bridges used for the traffic originally designed were safe, and that it was as irresponsible for engineers to build excessively strong bridges as excessively weak ones. He approvingly quoted a Professor Unwin:
If an engineer builds a structure which breaks, that is a mischief, but one of a limited and isolated kind, and the accident itself forces him to avoid a repetition of the blunder. But an engineer who from deficiency of scientific knowledge builds structures which don’t break down, but which stand, and in which the material is clumsily wasted, commits blunders of a most insidious kind.
In other words, Unwin, like Cooper, believed that bridges should be made strong enough to perform their function but not so strong that they are heavier and more expensive than they have to be. This view has always been and always will be shared by the best of engineers, for they recognize that in the final analysis engineering is part of a much larger social enterprise, and money spent unnecessarily for civil-engineering structures becomes unavailable for other civic endeavors, or for initiatives of a humanitarian kind. The line between too little and too much safety is not always very clear and distinct, however, and that is what makes the best engineering also the most difficult. It is also what can lead to the worst engineering.
Cooper’s reputation was so solid in 1894 that he was appointed by President Grover Cleveland to a commission of five expert engineers that was to recommend the length of span which would be safe and practical for a bridge across the Hudson River at New York City. Two competing bridge companies had proposed two competing bridge types, one a cantilever and one a suspension bridge. The cantilever would have had a span greater by three hundred feet than the recently completed Forth Bridge, and the suspension bridge, with a thirty-one-hundred-foot main span, would have been almost twice as long as the Brooklyn Bridge. The commission’s rejection of a cantilever in favor of a suspension bridge for this dramatic site touched off a debate that was to last for years, and would include considerations relating to the interference with shipping, the length of the maximum possible suspension bridge, and the alternative of tunnels under the Hudson. That saga will take the entire next chapter to relate.
Engineering News, in part because it was based in New York, took considerable interest in the issue of bridging the Hudson, and the extended discussion of cantilever bridges in its pages prompted one reader, perhaps unfamiliar with the discussion of the word that had taken place years earlier, to inquire as to why that spelling was used, rather than “cantaliver,” as recommended by the Century Dictionary. Engineering News admitted that, whereas it followed that “eminent authority” in such Americanized spellings as “center” and “gage,” it preferred the “cantilever” spelling “as being more euphonious and as least upsetting long-established and well-nigh universal usage.” The editors went on to reopen the question of etymology, admitting that “the origin of the word is uncertain,” an opinion to be echoed by the ponderous and authoritative Oxford English Dictionary, in which “no satisfactory suggestion could be offered” for the word that had become ever more familiar to many engineers and laypersons alike. According to Century, the editors reported, the “probable original … was ‘quanta libra,’ of what weight or balance,” and this led to the dictionary’s spelling preference. Nevertheless, the Universal Dictionary, copyrighted in 1897, was to relegate the spelling “cantaliver” to “unusual” status. Under the definition of the word relating to bridge building, this dictionary credited, perhaps because of the popularity of Benjamin Baker’s lecture and its human model, the Japanese with “the earliest known application of the principle,” and described quite precisely the already “celebrated Forth Bridge” as comprising a “double cantilever (of 1,360 ft. length) … connected by girders 350 ft. long,” thus adding up to the remarkable 1,710-foot spans that impressed Cooper and so many of his contemporaries.
The Forth Bridge had clearly become the cantilever of the world, to the virtual exclusion of its progenitors. Under the entry “cantilever bridge,” for example, the Universal again was quite technically correct in describing such a structure as one “constructed on the cantilever system, the two sides being pushed out towards the centre and supported by a greater weight on land, until they meet and are joined at the centre.” Though the dictionary acknowledged that “numerous important bridges” were built on the principle, none were named in the entry. The temporary superstructure of the Eads Bridge in particular was no more mentioned in this American dictionary than it was in Baker’s lecture. Yet it was Eads who, almost three decades earlier, in his argument for the advantages of the arch over the truss, had so convincingly employed the bent, angled, or canted lever to make his point for his design for a bridge across the Mississippi. Indeed, according to Cooper, who could take personal pride in its construction, the St. Louis bridge was “the first practical solution of the cantilever principle on a large scale.” He went on to observe that “the erection of two balanced cantilevers, each over 250 feet, with ease, safety and economy, made clear to the mind of engineers that the cantilever was the economic method of erecting long spans over deep gorges or rivers, where ordinary methods of scaffolding would be too expensive, or subject to great risks, or where navigation forbids the obstruction of the waterway.” In fact, to the casual observer, photographs of the Eads Bridge under construction can be easily mistaken for those of the Forth Bridge. I once assembled a series of slides for a lecture by squinting at them before a light bulb and was later embarrassed to find that the Eads Bridge under construction had been projected on the screen while I was describing the Forth.
An early proposal for a cantilever bridge across the St. Lawrence River at Quebec (photo credit 3.14)
Cooper would not have made such a mistake. He did, however, near the end of his career, supervise the construction of a great cantilever from such a distance as to lose sight of some of the details that earlier he had written about so authoritatively. The history of his bringing to reality the idea for a bridge across the St. Lawrence River, near the city of Quebec, is, like the history of virtually all great bridges, long and arduous. A span was proposed as early as 1852 by Edward Wellman Serrell, who had by then designed and built the Lewiston & Queenston Suspension Bridge over the Niagara River between New York and Canada. That bridge was advertised as the “Largest in the WORLD!!!” because its stone towers atop the bluffs were 1,040 feet apart, but its deck was only 849 feet long because of the manner in which it joined the shores below the bluffs. Guy wires, mimicking those on Roebling’s nearby Niagara Gorge Suspension Bridge, were added after a storm in 1855, but they were detached in early 1864, when they were threatened by an ice jam that had formed in the river. The guys were still unfastened when a gale struck on the first day of February of that year, and the bridge was destroyed. Serrell’s proposal for a railway and highway bridge at Quebec was not acted upon at the time, but the site he identified was to become the location for another ill-fated bridge more than forty years later.
The Quebec Bridge Company was incorporated in Canada in 1887, with the authority to issue bonds and the right to build a railway bridge that might also serve for pedestrians and vehicles to cross the St. Lawrence River. Construction was to begin within three years, but three extensions were granted by Parliament, with the last due to expire in 1905. Though other legislation changed the name of the organization to the Quebec Bridge & Railway Company, it continued to be known by its shorter name. Legislation also declared the bridge to be for the general advantage of Canada, and so subsidies were granted to allow the work to begin in earnest.
In 1897, E. A. Hoare, chief engineer of the bridge company, wrote to the president of the Phoenix Bridge Company in Pennsylvania and asked that any of its engineers planning to attend the annual meeting of the American Society of Civil Engineers in Quebec that June stop in to see him regarding a bridge project. Among those attending the meeting was John Sterling Deans, chief engineer of Phoenix, and he and many other visiting engineers were taken to the bridge site. Also in the group was Theodore Cooper, and within about a week Deans had written to Hoare that Cooper would be happy to lend his experience to the project, which called for a bridge with piers sixteen hundred feet apart. When invitations to bid were issued in 1898, specifications for a cantilever bridge were included; bidders proposing any other kind of bridge would have to provide their own specifications. Among the tenders received were four cantilever and three suspension-bridge designs, including a cantilever from the Keystone Bridge Company and both a cantilever and a suspended span from the Phoenix Bridge Company. Since any type of bridge at Quebec would necessarily be on a massive scale, the advice of an experienced consulting engineer was sought, and Theodore Cooper agreed to review all the plans and tenders. In spite of his prior relations with Phoenix, Cooper’s integrity as an engineer was believed to be above favoring their design for any but sound technical and economic reasons.
Cooper preferred the cantilever designs, because he believed them to be realizable at a lower cost than suspension-bridge alternatives. In mid-1899, he reported to the Quebec Bridge Company his conclusion that the Phoenix cantilever design was indeed the “best and cheapest” overall. (In fact, Keystone’s design was considerably less expensive per ton of steel, but it was more costly overall, since the bridge itself would have been much heavier.) Along with his recommendation, Cooper called for further exploration of the riverbed, in order to establish the final position of the bridge’s foundations and thus set a final determination of its length. Deeper foundations, for example, could require more time and money to construct than would a longer span. In early 1900, Cooper had the additional information he had requested; after studying the situation for three months, he concluded that the original pier locations, sixteen hundred feet apart, would take a year longer and be accompanied by more “real and imaginary contingencies” than shallower piers farther apart, and he recommended increasing the main bridge span to eighteen hundred feet—thus proposing a cantilever bridge with a span longer than any in the world.
In the meantime, negotiations were going back and forth between the Quebec and Phoenix companies, with the latter concerned about the financial status of the former. Detailed design work did not progress very quickly under such circumstances, for Phoenix was not assured of being paid for its services. It was not until 1903, when plans for a National Transcontinental Railway project were revealed, that a bridge at Quebec became such a necessity that government backing was assured. By then the government had also become more interested because of planning for the Quebec Tercentenary in 1908, and it was intimated that the bridge should be ready for the celebration. Thus the pace of design work was suddenly accelerated in 1903—with consequences that were only to be realized years later.
Cooper’s changes relevant to an eighteen-hundred-foot span were sent to Phoenix, where Peter L. Szlapka, the company’s design engineer, raised some questions about the degree to which some of the steel was stressed. In the final analysis, however, the exceptional magnitude of the structure was invoked as justification for the exceptional loading of its parts. The new specifications were submitted to Collingwood Schreiber, chief engineer of the Department of Railways and Canals, for the required government approval, and Schreiber proposed to his superior that the department “employ a competent bridge engineer to examine from time to time the detailed drawings of each part of the bridge as prepared, and to approve of or correct them,” and submit them to Schreiber for final approval. When Cooper learned of this, he wrote to Hoare at Phoenix: “This puts me in the position of a subordinate, which I cannot accept.… I have written to Mr. Schreiber that I do not see how such an engineer could facilitate the progress of the work or allow me to take any responsible steps independently of his consent.” In other words, Cooper wanted to have the last word on, and the full credit for, the design of the longest bridge in the world. A couple of weeks later, Cooper went to Ottawa to meet personally with Schreiber, after which the minister of railways and canals was advised that, “provided the efficiency of the structure be fully maintained up to that defined in the original specifications attached to the company’s contract, the new loadings proposed by their consulting engineer be accepted.” Though all plans were to continue to be submitted to Schreiber, Cooper was, for all practical purposes, to be the final authority.
Theodore Cooper, like Benjamin Baker, never married; their bridges were their children. As the Forth Bridge was Baker’s magnum opus, so the Quebec was to be Cooper’s. Cooper had few equals in America, but at the time of his involvement in the Quebec Bridge he was an elderly man in poor health, which pretty much kept him confined to New York. Though he had visited the Quebec site on several occasions while the piers were being constructed, he never once went to Quebec during the erection of the steel superstructure. Cooper may have been “de facto, chief engineer,” and thus ultimately responsible for checking every aspect of the bridge design, but he had no staff in New York to assist him. The design of the bridge, as far as selecting the sizes of members and checking that they were not overloaded, was done to Cooper’s specifications and modifications at the Phoenix Bridge Company by Szlapka, a German-trained engineer who over the course of twenty-odd years with Phoenix had worked on many major projects. Szlapka was, however, a desk engineer, without experience in the erection phase of bridge building, and so was not necessarily in a position to judge the structure itself on his own visits to the construction site. Yet Cooper, who was known for his hypercritical disposition, had full confidence in Szlapka’s work, accepting it on faith when Cooper could not study it thoroughly himself; he had little concern in 1907 that the bridge was progressing in any but a normal fashion.
The south arm of the Quebec Bridge had been cantilevered out about six hundred feet over the St. Lawrence River by early August 1907, when it was discovered that the ends of pieces of steel which had been joined together were bent. Cooper was notified, by letter, by Norman R. McLure, a 1904 Princeton graduate who was “a technical man” in charge of inspecting the bridge work as it proceeded, who suggested some corrective measures. Cooper sent back a telegram rejecting the proposed procedure and asking how the bends had occurred. Over the next three weeks, in a series of letters back and forth among Cooper, chief engineer Deans, and McLure, Cooper repeatedly sought to understand how the steel had gotten bent, and rejected explanation after explanation put forth by his colleagues. Cooper alone seems to have been seriously concerned about the matter until the morning of August 27, when McLure reported that he had become aware of additional bending of other chords in the trusswork and, since “it looked like a serious matter,” had the bends measured; he explained that erection of additional steel had been suspended until Cooper and the bridge company could evaluate the situation.
Yet, even as McLure went to New York to discuss the matter with Cooper, Hoare, as chief engineer of the Quebec Bridge Company, had authorized resumption of work on the great cantilever. As soon as McLure and Cooper had discussed the bent chords, Cooper wired Phoenixville: “Add no more load to bridge till after due consideration of facts.” McLure had reported that work had already been suspended, and so contacting Quebec more directly was not believed to be urgent, but when McLure went on to Phoenixville, he found that the construction had in fact been resumed. Some conflicting reports followed, thanks in part to a telegraph strike then in progress, as to whether Cooper’s telegram was delivered and read in time for Phoenixville to alert Quebec.
In any event, the crucial telegram lay either undelivered or unread as the whistle blew to end the day’s work at 5:30 p.m. on August 29, 1907. According to one report, ninety-two men were on the cantilever arm at that time, and when “a grinding sound” was heard, they turned to see what was happening. “The bridge is falling,” came the cry, and the workmen rushed shoreward amid the sound of “snapping girders and cables booming like a crash of artillery.” Only a few men reached safety; about seventy-five were crushed, trapped, or drowned in the water, surrounded by twisted steel. The death toll might also have included those on the steamer Glenmont, had it not just cleared the bridge when the first steel fell. Boats were lowered at once from the Glenmont to look for survivors, but there were none to be found in the water. Because of the depth of the river at the site, which allowed ocean liners to pass, and which had demanded so ambitious a bridge in the first place, the debris sank out of sight, and “a few floating timbers and the broken strands of the bridge toward the … shore were the only signs that anything unusual had happened.” The crash of the uncompleted bridge “was plainly heard in Quebec,” and the event literally “shook the whole countryside so that the inhabitants rushed out of their houses, thinking that an earthquake had occurred.” In the dark that evening, the groans of a few men trapped under the shoreward steel could be heard, but little could be done to help them until daylight. The sounds of the bridge falling and the moans of the lives it claimed would echo around the world for days, weeks, and years to come.
The south arm of the Quebec Bridge, as it appeared just before its collapse on August 29, 1907 (photo credit 3.15)
Within days, the story of the unread telegram was reported as part of the tragedy. According to one version, Cooper filed it in New York before noon and, though delayed by the strike, the wire did reach Quebec in the middle of the afternoon—in time to save the men, if not the bridge. Cooper was first reported to have said that the message included an admonition to get off the bridge at once, but in fact it called only for halting the addition of any more steel to the structure. The less-than-urgent-sounding message thus lay on Deans’s desk until he returned to his site office at about 5 p.m., shortly before McLure himself returned from New York. Even if it had not been too late to clear the structure, no warning might have been given, for the halt asked by Cooper was in fact to buy time to analyze the anomalies that had developed in the structure. It is not clear that Cooper or anyone else believed that collapse was imminent.
Shortly after the accident, amid speculations as to its causes and as to whether the men might have been saved, Cooper was reported to have reproached himself “for not having visited the work in two years,” and confessed that he had “tried to obtain his release from the responsibility of serving as the consulting engineer” on the Quebec Bridge because of his poor health, but “the builders would not listen to that.” With regard to the ill-fated telegram, Cooper qualified earlier reports regarding its message and pointed out that, serving officially only as consulting engineer to the project, he had no authority to order the workmen off the structure.
A royal commission was formed immediately to inquire into the cause of the collapse of the Quebec Bridge. The commission comprised: Henry Holgate, a civil engineer from Montreal; John G. G. Kerry, a civil engineer from Campbellford, Ontario; and John Galbraith, dean of the Faculty of Applied Science and Engineering at the University of Toronto. The site was visited the day after the accident, and the taking of evidence commenced in Quebec within two weeks. Cooper himself, who remained in New York, was interviewed by the commission there for a week in mid-October. After the confusing and conflicting newspaper reports concerning what he had said about his telegram in the days immediately following the accident, Cooper had remained silent on the matter, until the commission visited “the Nestor of American bridge designers,” as Engineering News identified him in its report on the visit, thus raising his reputation to mythic proportions. Although he was actually sixty-eight at the time, he was described as “now 70 years of age” and as having been “in poor health for several years.” The trade journal’s sympathetic portrait of the engineer was no less deferential than the commission’s treatment of him:
The Canadian Commission, therefore, which spent the week from Oct. 14 to Oct. 19 in New York City, visited Mr. Cooper at his residence, conferred with him concerning the matter on several successive days, as his strength permitted, and finally formulated a series of questions covering the matters pertinent to the inquiry. Replies to these questions were dictated by Mr. Cooper at his leisure, and this testimony, after its reduction to writing, was fully reviewed and revised by the Commission and Mr. Cooper in further conference, until it represented as completely as the Commission could determine, the full testimony which Mr. Cooper was able to give.
By the end of the month, the questions of the commission and Cooper’s responses were reprinted in full in Engineering News. The transcript showed that the commission was looking into the entire history of the bridge project, the involvement and interrelationship of Cooper, the Phoenix Bridge Company, and the Quebec Bridge Company, and the nature of the various organizations and their respective involvement in the design and oversight of the work. Among the leading questions posed to Cooper was whether the plans were approved to his satisfaction or whether he would have given them further study had he been able to do so. His reply was that of a man seeking sympathy:
I should have been glad to have had the physical strength and the time allowed me to have given further study to many parts of this structure, but in my physical condition I have been compelled, and must accept the responsibility for the same, to rely to some extent upon others. I had and have implicit confidence in the honesty and ability of Mr. Szlapka, the designing engineer of the Phoenix Bridge Co., and when I was unable to give matters the careful study that it was my duty to give them, I accepted the work to some extent upon my faith in Mr. Szlapka’s ability and probity.
Engineering News, in a prefatory editorial to its printing of Cooper’s testimony, cautioned engineers to “maintain a judicial attitude in considering the serious question how responsibility should be apportioned for faults in design, construction and erection.” Indeed, the trade publication reminded its readers, “every engineer will recognize the fairness of suspending judgment as he reads Mr. Cooper’s statement until the statements of the Phoenix Co. engineers are presented.”
After taking Cooper’s testimony in New York, the commission traveled to Phoenixville and Philadelphia to collect further information and take testimony from the Phoenix Bridge Company and its officers and engineers, including Szlapka. Here the commission heard “vigorous language directed against Theodore Cooper,” which included charges that he had played down concerns over the incomplete bridge’s structural behavior when it was questioned by the company’s engineers, that he allowed more stress on the materials in this bridge than in any previous structure, that he ordered the main span increased to eighteen hundred feet, and that he refused to visit the Phoenixville plant where the first parts made for the bridge were being assembled.
The commissioners delivered their report, to which was appended a “Report on Design of Quebec Bridge” by C. C. Schneider, within six months of the accident. Among the main findings of the inquiry were that the collapse was initiated by the inability of the lower chords near the main pier to withstand the high though not unexpected compression loads to which they were subjected. Szlapka had designed these chords, and Cooper had examined and approved them, and their failure “cannot be attributed directly to any cause other than errors in judgment on the part of these two engineers.” The report continued:
These errors of judgment cannot be attributed either to lack of common professional knowledge, to neglect of duty, or to a desire to economize. The ability of the two engineers was tried in one of the most difficult professional problems of the day and proved to be insufficient for the task.… A grave error was made in assuming the dead load for the calculations at too low a value and not afterwards revising this assumption.… This erroneous assumption was made by Mr. Szlapka and accepted by Mr. Cooper, and tended to hasten the disaster.
In short, what Szlapka had done was to let stand an educated guess as to the weight of steel that the finished bridge would contain. Such guesses, guided by experience and judgment, are the only way to begin to design a new structure, for without information on the weight of the structure the load that the members themselves must support cannot be fully known. When the loadings are assumed, the sizes of the various parts of the bridge can be calculated, and then their weight can be added up to check the original assumption. For an experienced engineer designing a conventional structure, a final calculation of weights only serves to confirm the educated guess, and so such a calculation may not even be made in any great detail. In the case of a bridge of new and unrealized proportions, however, there is little experience to provide guidance in guessing the weight accurately in the first place; a recalculation, or a series of iterated recalculations, is necessary to gain confidence in the design. (The situation is not unlike that of a veteran weight guesser at a carnival, who might be expected to predict quite well the weights of normal-sized fairgoers but not the weights of dwarfs or giants, who fall outside the range of even sideshow experiences.) According to the findings of the commission, “the failure to make the necessary re-computations can be attributed in part to the pressure of work in the designing offices and to the confidence of Mr. Szlapka in the correctness of his assumed dead load concentrations. Mr. Cooper shared this confidence.” Since Cooper was well known to have a “faculty of direct and unsparing criticism,” his confidence in Szlapka’s design work went unquestioned.
Just as Cooper had confidence in Szlapka’s work, so did the resident engineer at the construction site have confidence in the work of them both. When a construction foreman expressed serious concern over the condition of the fatal member, the resident engineer thought the matter of little importance, telling the foreman, “Why, if you condemn that member, you condemn the whole bridge.” After the collapse, it was reported that the resident engineer “had confidence in that failing chord because it was to him unbelievable that any mistake could have been made in the design and fabrication of the huge structure over which able engineers had toiled for so many years.” As a result of the accident, however, Engineering News reported that mistakes of all kinds had become more believable.
The underestimation of the true weight of the bridge had actually come to Cooper’s attention earlier in the design process, but only after considerable material had been fabricated and construction had begun. At this time, a recalculation of the stresses in the bridge led Cooper to consider that the error had meant that some stresses had been underestimated by 7–10 percent. All structures are designed with a certain margin of safety; he felt the error had reduced that margin to a small but acceptable limit, and so the work was allowed to proceed. In fact, some of the effects of the underestimated weights were, in the final analysis, of the order of 20 percent, and this was beyond the margin of error that the structure could tolerate.
In its discussions of the various bridge-building organizations involved and their respective faults, the inquiry commission was clear regarding the sense of hubris and overconfidence that success can bring to an organization. In this regard, the Royal Commission anticipated in some ways by eight decades what the Presidential Commission would find in its investigation of the space shuttle Challenger’s accident. Although there do not seem to have been too few assistants in that more recent accident, there certainly seem to have been too many overconfident bosses, or at least too many bosses willing to make compromises for other than purely technical ends. According to the Royal Commission, reporting in 1908:
Mr. Cooper states that he greatly desired to build this bridge as his final work, and he gave it careful attention. His professional standing was so high that his appointment left no further anxiety about the outcome in the minds of all most closely concerned. As the event proved, his connection with the work produced in general a false feeling of security. His approval of any plan was considered by every one to be final, and he has accepted absolute responsibility for the two great engineering changes that were made during the progress of the work—the lengthening of the main span and the changes in the specification and the adopted unit stresses. In considering Mr. Cooper’s part in this undertaking, it should be remembered that he was an elderly man, rapidly approaching seventy, and of such infirm health that he was only rarely permitted to leave New York.
Mr. Cooper assumed a position of great responsibility, and agreed to accept an inadequate salary for his services. No provision was made by the Quebec Bridge Company for a staff to assist him, nor is there any evidence to show that he asked for the appointment of such a staff. He endeavoured to maintain the necessary assistants out of his own salary, which was itself too small for his personal services, and he did a great deal of detail work which could have been satisfactorily done by a junior. The result of this was that he had no time to investigate the soundness of the data and theories which were being used in the designing, and consequently allowed fundamental errors to pass by him unchallenged. The detection and correction of these fundamental errors is a distinctive duty of the consulting engineer, and we are compelled to recognize that in undertaking to do his work without sufficient staff or sufficient remuneration both he and his employers are to blame, but it lay with himself to demand that these matters be remedied.
The issues raised in the report were to reverberate throughout the engineering profession for many years to come, and in some form remain as issues today. Engineering work, especially relating to novel and untried projects, requires considerable time for thinking and rethinking about assumptions and tentative solutions, often among a broad range of colleagues and even in public forums. In cases like the Forth Bridge, the time and openness have been repaid in structures that stand as monuments. The very success of once bold endeavors like the Forth Bridge, however, can lead engineers like Cooper into a sense of security concerning ostensibly similar designs that may not be warranted. Incidents like the Quebec Bridge collapse provide rude awakenings, as Engineering News reported within weeks of the accident: “The Quebec Bridge collapse has been an object lesson to every structural designer; and we risk nothing in saying that in a thousand offices, stress computations are being checked over and details of design are being investigated and discussed with greater care and thoroughness than ever before.”
The collapse of the Quebec Bridge, like that of the Tay, did not remove the need for a bridge at the location. Indeed, one could almost say there was renewed resolve to show that it could be done—and done right. The new design that was finally chosen was described at the time as “commonplace in appearance and costly to build.” This should not have been surprising, for matters of aesthetics and economy, so important when bridges are first planned, come to appear almost as luxuries in the wake of a tragedy of the magnitude of that which occurred on the St. Lawrence River in 1907. The bridge that was finally built at the site of the wreckage reinstated the look of straight bottom chords, which Szlapka had testified had been changed to curved ones “for the sake of artistic appearance.” Its outline did make the structure easier to analyze for load and stress distribution, but what was more significant about the new design was that it was a heavier and more substantial-looking bridge. If Cooper’s Quebec seemed to have the lightness of the Tay Bridge, the redesigned Quebec would appear to have the firmness of the Forth.
The collapse of the first Quebec Bridge in 1907 had a profound and immediate effect on the direction of bridge building worldwide. New York’s Queensboro Bridge, whose more lacy and graceful cantilever design with a maximum span of almost twelve hundred feet is often mistaken for that of a suspension bridge, was under construction when the Quebec collapse occurred. The Queensboro was completed in 1909 amid considerable protest and concern over its safety in particular, as well as over the safety of the entire genre. A second mishap in Quebec—which would occur in 1916, when the closing span of the redesigned structure fell to the bottom of the river while being hoisted into place, would reinforce reservations about the form. In spite of the resolve of the Canadian government to complete a successful cantilever design across the St. Lawrence River and thus vindicate the original decision, no other major cantilever bridge would be completed until the 1930s. To this day, none but the Forth comes within a hundred feet of the eighteen-hundred-foot span of the Quebec.
The incidents at Quebec were naturally the subject of doubting editorials in newspapers and trade journals alike, for both the public and the profession took a keen interest in record-setting bridge building. Nevertheless, according to Engineering News-Record, “Twice the hopes of success have been dashed, but never in the heart of the true engineer was there doubt that the enterprise would be brought to a successful conclusion.” As with all failures, there were lessons learned in the collapse of the first bridge and the subsequent embarrassment during the final stages of the second, and it was the knowledge contained in these lessons that gave engineers the understanding to attack the problem of bridging the St. Lawrence with renewed confidence even in the wake of defeat, and enabled them in the end to “have vindicated the profession before a doubting world.”
A variety of designs submitted for the rebuilding of the Quebec Bridge (photo credit 3.16)
Years before the second Quebec accident, some members of the profession had their own concerns and prejudices about the whole process of choosing a bridge design. Among the most prominent and vocal of these was Gustav Lindenthal, who at the time of the Quebec collapse was a consulting engineer in New York City. Lindenthal had prepared the suspension-bridge proposal that the Phoenix Bridge Company had submitted along with its winning cantilever design in the original Quebec Bridge competition. He had also prepared a modified suspension-bridge design in response to the invitation by the board of engineers constituted to design a new bridge. This board had come up with specifications and with its own official concept, a cantilever structure with a straighter and bulkier outline than that of the collapsed structure. However, when bids were invited from construction companies, they were also given the option of submitting their own designs, though a company that did so had to assume “the entire responsibility not only for the materials and construction of the bridge, but also for the design, calculations, plans and specifications and for the sufficiency of the bridge for the loads” specified.
A comparison of the cross sections of the lower-chord members of various late-nineteenth- and early-twentieth-century bridges (photo credit 3.17)
Three members of the board of engineers for the redesigned Quebec Bridge standing inside one of the lower-chord members (left to right: Ralph Modjeski; C. N. Monsarrat, chairman and chief engineer; and C. C. Schneider)(photo credit 3.18)
Lindenthal, in private practice as a consulting engineer, was personally and professionally outraged by such a condition, and he was greatly disappointed that the design chosen for the second Quebec Bridge was another cantilever, this one proposed by the St. Lawrence Bridge Company. The accepted design differed from the official one mainly in its central span of 640 feet, which was to be fabricated separately about three miles away, floated on barges to the bridge site, and hoisted into place between the 580-foot cantilever arms. After the choice had been made, Lindenthal wrote a lengthy tract entitled “Notes on the Quebec Bridge Competition,” printed in two successive issues of Engineering News, which was published every Thursday in New York City. Although it identified itself at the time as “a journal of civil, mechanical, mining and electrical engineering,” Engineering News concentrated on matters relating to large civil-engineering projects, especially those that had some connection to New York or to New York engineers like Lindenthal. The journal seems to have prided itself on publishing details of proposed, in-progress, and completed engineering projects, and the larger, more visible, and more expensive the projects it could report on, the better.
The second Quebec Bridge accident, showing the central span buckling upon impact with the water (photo credit 3.19)
Lindenthal’s notes on the Quebec Bridge competition had been introduced by an editorial, which had called it “the most important international competition for the design of a great engineering structure which has ever been held.” The potential value of such a competition was, of course, that the various alternative designs emanating from the minds of creative engineers with a wide range of experience and vision provided an excellent opportunity for the comparison of the different proposed bridge types, and thereby the opportunity for understanding their relative strengths and weaknesses. A given engineer, especially within the limited time between the announcement of a design competition and the deadline for submission, may only be able to pursue in sufficient detail one or two designs. Decisions must necessarily be made at the outset as to whether to explore a cantilever or a suspension-bridge design or both, for example. If the engineer or the bridge company he is associated with is without work, considerable time may be available to be devoted to speculation on the competition, in the hopes of winning. If the engineer or his firm is already busy with other projects, a decision has to be made as to whether to hire additional engineers to work on those, so that a new design may be developed for the competition, or to try to find some spare time to think in new directions. In all cases, there is the question of how the time will be compensated for, and this was a point of major and emotional emphasis in Lindenthal’s notes on the Quebec competition.
According to Lindenthal, the official design and the specifications upon which tenders were invited were prepared by the Board of Engineers “after much labor and time” over a two-and-a-half-year period at a cost to the Canadian government of about $500,000. The bidders, on the other hand, “were expected to make their competitive designs without compensation and in four months’ time.” Lindenthal believed that one way such a competition could work was as follows:
If five or more of the world’s bridge firms had been invited to prepare competitive designs, on a proper general specification, in six months’ time, and for a compensation to cover expenses, then at 20% of the cost of the official design (which afterwards was ignored) and in less than one-quarter of the time there would have been a choice from a number of superior plans with tenders thereon, which would have represented the best practice and advance in the art.
Lindenthal went into some detail about the matter of compensation for engineering services for more than pecuniary, self-serving reasons. He had long been an outspoken advocate for structures transcending the utilitarian, and for more respect for the engineering profession. Under a section of his notes entitled “Causes of the Disaster,” Lindenthal stated clearly that “the primary cause of both disasters”—namely, the 1907 collapse of the Quebec cantilever under construction and the 1879 fall of the high girders of the Tay Bridge—was simply “bad engineering.” But, rather than going on to detail technical causes, Lindenthal wrote about matters that were to become increasingly the topic of letters, editorials, and articles in Engineering News and other professional publications of the time. In connection with the Quebec Bridge, he wrote, there was “a contributory circumstance of which it is difficult for engineers to speak without a feeling of humiliation.” This circumstance was not only “the beggarly compensation for engineering services on a work of unprecedented magnitude,” but also “the willingness of an engineer of high reputation and unimpeachable integrity to assume very important and laborious duties for a fee for which they could not possibly and seriously be met.”
Lindenthal admitted that the financial conditions of a company “during the incubation of large work” could be weak, so that the engineers and other professionals “aiding in its promotion” might be quite satisfied to take only nominal compensation until financing was secured and they could be fully paid. His comments vis-à-vis the Quebec Bridge project in particular are well worth quoting at length, because, using Theodore Cooper’s experience as representative, they set down issues that were on the minds of an increasing number of engineers in the early part of the twentieth century, and they provide insight into the practice of engineering generally:
While the Quebec Bridge Co. was struggling along, it could not pay more than a small amount for engineering advice. It got its plans for the bridge from contractors for nothing. But after the money, with the aid of the Canadian Government, was assured, the large and difficult engineering work should have been thoroughly taken in hand, through an efficient engineering organization, properly compensated.
Mr. Theodore Cooper, who as Consulting Engineer had assumed the largest share of responsibility, had no such organization and could not afford to have it. The fee of $3,750 per year, which he received for his services, was hardly enough to pay office rent and a stenographer. Most unfortunately Mr. Cooper seemed unable to see the wrong he did to himself, to the profession and to his clients, when he did not advise and explain to the last-named that neither he nor any other engineer could conscientiously undertake the important duties without adequate facilities and a competent working staff, and the compensation should be made sufficient both for his services and theirs. His action was a grievous wrong to the engineering profession, as it tended to create the impression that responsible engineering service was of little account and could be had for next to nothing, provided contractors’ plans were furnished.
It is most pathetic to notice from the testimony how Mr. Cooper endeavored to serve his employers faithfully, unselfishly but mistakenly. With a proper engineering organization it would not have been necessary to rely in any degree upon the office work and strain sheets of the contractors. Entirely independent computations could and should have been made by the responsible engineer, and the errors in the assumption of dead-load would have been discovered before construction began. Systematic study and analysis could also have been given to the contractor’s design to determine whether and where modifications in form and details, as for instance in the compression members, must be made for greater safety.
These thoughts, as here mentioned with the kindliest spirit to Mr. Theodore Cooper, an old and valued friend, are more particularly intended to call attention to a most essential requirement of good engineering service on large work, and that is resolute and great executive ability, which is rarer even than great technical ability. The failure of everyone concerned to recognize the importance of that requisite in the engineer’s work contributed greatly to the failure of the bridge.
The editors of Engineering News recognized that the objection could be raised that “Mr. Lindenthal was one of the participants in the competition and is therefore biased in his views,” but they defended their publication of what was at times the embarrassing diatribe of a loser by appealing to the author’s reputation, which by then had surpassed Cooper’s. The editors were sure that it would be generally agreed that “in the entire engineering profession of this or any other country there is hardly an engineer who is so competent by experience and ability to deal with the problem of long-span bridge design than Mr. Lindenthal.” Indeed, Engineering News could have its own objectivity questioned: it had for two decades advocated Lindenthal’s design for a great suspension bridge to span the Hudson River at New York, a project for the likes of which engineers such as Lindenthal himself were not to be much compensated, if at all, unless the project reached fruition. Ironically, Cooper, whom Lindenthal so severely criticized, had, of course, been among the distinguished engineers in favor of a suspension bridge across the Hudson.
The completion of the Quebec Bridge finally occurred in 1917; the distractions of a world war may have partly accounted for the lack of publicity accompanying the opening of what has become a symbol of Canadian resolve. Theodore Cooper had retired the year the first Quebec bridge fell, and he spent the final twelve years of his life in New York City, where he had set up his consulting practice in 1879. When Cooper died, in 1919, almost two years had passed since the Quebec Bridge had finally been completed, and there was less than a week till the twelfth anniversary of the collapse of the structure that was to have been his final work. His obituary in The New York Times declared that he “foresaw” the Quebec disaster, and reported that nearly one hundred lives would have been saved “had a telegram sent by Mr. Cooper been received and heeded.” The obituary in Engineering News-Record, perhaps three times as long as that in the Times, provided no such amelioration of Cooper’s role in the Quebec accident but mentioned the bridge only in passing as among the many projects included in the “consulting work” of the “famous bridge engineer.” Similarly, the memoir of Cooper that appeared two years later in the Transactions of the American Society of Civil Engineers treated his involvement in the Quebec Bridge project as only a passing credit, with no mention of the discredit it was in fact to his own and the professions reputation. Since these sources provided the information on Cooper’s life as presented subsequently in the Dictionary of American Biography, it too omits all mention of his role in the Quebec failure.
The completed Quebec Bridge (photo credit 3.20)
The scale of the Quebec Bridge shown by a guard posted during World War I (photo credit 3.21)
The obituaries and memoirs of Cooper were kind in their words of remembrance, but their generally short length belied their unqualified evaluation of his professional life, which encompassed so much of the latter part of nineteenth- and the early years of twentieth-century engineering. He was, after all, the 1858 civil-engineering graduate of Rensselaer Institute who then had begun his career working on the Hoosac Tunnel; who had entered the U.S. Navy at the outbreak of the Civil War and served on boats ranging from the Chocura out of Boston to the Nyack in the South Pacific; who had served as instructor at the Naval Academy in Newport, Rhode Island, and in the new Department of Steam Engineering at Annapolis; who had left the navy as first assistant engineer after Captain Eads appointed him inspector of steel being made for the bridge across the Mississippi; who had taken charge of the erection of the steel by the cantilever method for the great bridge at St. Louis; who had succeeded Eads as engineer of the bridge-and-tunnel company after Eads moved on to construct jetties and promote his dream of a ship railway; who had joined successively the Delaware Bridge Company and the Keystone Bridge Company, rising to assistant general manager of the latter; who had designed and built shops for the Mexican National Railroad; who had remodeled and rebuilt a plant for the Lackawanna Coal and Iron Company; and, with all this experience behind him at the relatively young age of forty, in 1879, had established himself as a consulting engineer in New York City, where twenty years earlier the iron magnate and philanthropist Peter Cooper, no relation to Theodore, had founded the Cooper Union for the Advancement of Science and Art.
Theodore Cooper, as pictured in an obituary (photo credit 3.22)
Theodore Cooper’s experience, coupled with the reputation he had established with his publications on bridge design and construction, especially with regard to the loadings to which increasingly heavy locomotives subjected steel bridges, had opened up many opportunities for him. In New York City alone, he had worked on projects involving a bridge over the Harlem River, on the first elevated railways, on the New York Public Library, as one of five engineers appointed by President Cleveland to determine the maximum span of a bridge proposed to cross the Hudson River, and as a member of the board of experts who evaluated a design of the Manhattan Bridge. In the context of such a distinguished and varied career, the Quebec Bridge may indeed have appeared to contemporary editors as an inappropriate focus for an obituary.
In spite of all that had been written of Cooper’s inadequate compensation for his work on the Quebec Bridge, he did not die a pauper. His total assets amounted to about $180,000, the great majority of that in stocks and bonds, mostly in the American Telephone and Telegraph Company. Since Cooper never married, he left the bulk of his estate to a dozen nieces and nephews. The main beneficiaries were the two nieces, Alice and Mary Cooper, who had lived at the same West 57th Street address as their uncle, and who together received about a quarter of his estate.
Cooper’s intangible and unspoken legacy was, however, the collapse of the Quebec Bridge. That event, no matter what its ultimate cause and who its agent, took the genre of the cantilever bridge from its previously high position of trust, which had been built up by Benjamin Baker’s lectures in the late 1880s on the principle generally and on the Forth Bridge in particular, to its low position of doubt and distrust after 1907. The single event of the Quebec Bridge failure thus altered the course of bridge development, especially in America, from that set by Eads at St. Louis with his articulate argument for and achievement of an arch over a suspension design. Fowler and Baker’s great cantilever over the Firth of Forth had created a further hurdle for proponents of suspension bridges to overcome in the late nineteenth and early twentieth centuries; that the Quebec Bridge was under construction as an even greater cantilever was in fact testimony to the growing competitiveness of the genre at the time. The collapse of the Quebec Bridge—Theodore Cooper’s dashed dream—greatly influenced the bridgescape across our rivers and the bridgeline of our cities to become what we know today.