PART TWO
8
The foundations for the support of these large masses of masonry must be unyielding.
—JOHN A. ROBELING
THE EASIEST way to explain how the caisson would work, Roebling and his assistants found, was to describe it as a huge diving bell that would be built of wood and iron, shaped like a gigantic box, with a heavy roof, strong sides, and no bottom. Filled with compressed air, it would be sent to the bottom of the river by building up layers of stone on its roof. The compressed air would keep the river out, help support the box against the pressure of water and mud, and make it possible for men to go down inside to dig out the riverbed. As they progressed and as more stone was added, the box would sink slowly, steadily, deeper and deeper, until it hit a firm footing. Then the excavation could stop, the interior of the box would be filled in solid with concrete, and that would be the foundation for the bridge tower.
The idea was quite simple really. Furthermore, it had been used successfully in Europe for more than a generation, first in France, where the word “caisson,” meaning “chest,” had originated, then later in England and Germany. An air lock that enabled workers to get in and out of a sealed chamber filled with compressed air had been devised as early as 1831 by Lord Thomas Cochrane, the controversial British admiral, and in 1851 a pneumatic caisson had been used on a bridge foundation for the first time, for piers in the Medway River at Rochester, England. Seven years after that Brunel had taken a caisson down more than seventy feet to build a pier for his last and greatest railroad bridge, the Royal Albert over the Tamar at Saltash, Cornwall.
But the caisson Roebling intended to sink beneath the East River on the Brooklyn side would be bigger by far than anything used in Europe or the few that had been used in the United States, and the one for the New York tower, it was then thought, would have to go thirty to forty feet deeper than even Brunel had gone.
The caisson the Roeblings had designed, and which in the late fall of 1869 began slowly to take shape at the Webb & Bell yards, was to be built like a fort and launched like a ship. A gigantic rectangular box, 168 feet long and 102 feet wide, it was to have nine and a half feet of headroom inside and overhead a roof of solid timbers five feet thick, bringing the total height of the box to fourteen and a half feet. In area it would be more than half the size of a city block, more than half the size of the new St. Patrick’s Cathedral, for example. The sides of the box were to be V-shaped, being nine feet thick where they joined the roof and tapering to a bottom cutting edge of just eight inches. The inside slope of the V would be at an angle of about forty-five degrees and the entire cutting edge, or “shoe,” would be shod with a heavy iron casting and sheathed the whole way around with boiler plate extending up three feet, inside and out. A heavy oak sill two feet square would rest on the casting.
Driftbolts, screw bolts, and wood-screw bolts would be used to secure the whole immense mass. The V-shaped sides would be fixed to the roof with heavy angle irons. At the corners, timber courses would be halved into each other and strapped together. The roof itself would be built of five solid courses of yellow pine “sticks”—timbers a foot square—laid up side by side and bolted both sideways and vertically.
To make the box airtight the seams would be caulked with oakum to a depth of six inches, inside and out, and between the fourth and fifth courses of roof timber, across the entire top of the structure and extending down all four sides, a vast sheet of tin would be put down. The tin on the outside would be further protected by a sheathing of yellow pine and the spaces between timbers would be filled with hot pitch.
Since Roebling had learned that air under pressure of forty or fifty pounds (or about what would be needed inside the work chamber) will readily penetrate ordinary wood, he had selected a yellow pine from Georgia and Florida that was so pitchy that the 12-by-12 sticks would not even float. And finally, just to be sure, he planned to coat the whole inside with a specially concocted, supposedly airtight varnish.
Once the caisson was launched, ten additional courses of timber would be added to the roof, thereby making it a solid timber platform fifteen feet thick, which would act like a colossal wooden beam for carrying and distributing the load of the tower.
As the work at Webb & Bell progressed on the raw and ungainlylooking structure, two air locks, two so-called supply shafts, and two water shafts were being built into the timber roof.
The air locks were made of half-inch boiler plate. They were cylindrical in shape, seven feet high by six and a half feet in diameter, or big enough to pack in about a dozen men, who would enter from the top, through an iron hatch about the size of a manhole cover. The hatch closed, an attendant stationed inside would open a valve near his feet, releasing compressed air from the work chamber below into the lock. As soon as a gauge on the wall of the lock showed the pressure there equal to that below, another hatch in the floor would be opened and the men, one by one, would climb down a ladder through an iron shaft, three a half feet in diameter, into the caisson itself.
When it was time to come out, the process would be reversed. They would climb up the shaft and into the air lock, the floor hatch would be secured, and another valve would be opened to release the air from the lock. When pressure in the lock decreased to normal atmospheric pressure, or 14.7 pounds per square inch, then the top hatch would be opened and the men would climb out. This way the loss of compressed air from the caisson each time a gang of men went in or out was no more than the volume of the lock.
The water shafts were a very simple but ingenious means by which the mud and rock excavated inside the work chamber could be hauled out with no loss of compressed air whatsoever, and with none of the time required to move through an air lock.
The water shafts were seven feet square, open at top and bottom, and they extended like twin wells through the roof of the caisson straight down into the work chamber to a depth nearly two feet below that of the caisson’s bottom edge. These shafts were also built of boiler plate and once the caisson was in operation they would be filled with water to a level sufficient to “lock in” the compressed air below.
At the base of the shafts, at the two points where they extended deeper than the caisson itself, open pits would be dug in the river bottom, which would also fill with water. These would be the delivery ends of the shafts and the columns of water within the shafts would be kept suspended (kept from flooding in on the workers) by the pressure of the air within the chamber.
The water shafts, as one magazine of the time explained for its readers, were essentially huge barometers that measured the pressure of the air inside the caisson. The shaft itself was the barometer tube, filled with water instead of mercury, and the pool at the bottom was the cistern. Every pound of pressure in the caisson above normal atmospheric pressure (which of course was bearing down on top of the column of water) forced the water a little more than two feet higher in the shaft.
To get rid of the material they excavated, the men would shovel it into the pits, or pools, at the base of the shafts, where it would be hauled up and out by big clamshell dredge buckets dropped down from above, directly through the shafts of water. The theory was the buckets could work as fast as the men could feed them. It was a neat, efficient system, so long as the water in the shafts stayed at the proper level. But if the volume of water in one shaft became too great—too heavy, that is, for the compressed air below to support it—then the water in the pit would flood out into the work area. Or, if for some reason, the volume of water decreased to the point where its weight was no longer enough to counteract the pressure in the chamber, then there would be a terrific release of air, or blowout, from below.
The supply shafts were only twenty-one inches in diameter and simply the means by which Roebling intended to get the necessary cement, sand, and gravel into the caisson once the excavation was finished.
John Roebling’s thought had been to make the interior of the caisson one big open space, with no divisions or supports to get in the way of the excavation work. But his son had to abandon that idea for several reasons. First of all, since the caisson would have to be launched like a ship—only in this case a ship built upside down—there would have to be supports of some kind between the launchways and the roof. Washington Roebling also anticipated that the cutting edge of the caisson would be striking on boulders on its way into the riverbed and when that happened he did not want the entire weight resting solely on those few points. But it was chiefly because of the particular nature of the East River that he decided to divide up the work chamber with a number of supporting walls.
The East River connects the Upper Bay of New York with Long Island Sound, and because it has two entrances—at the tip of Manhattan and at Hell Gate, the opening to Long Island Sound—and two distinct tidal movements arriving at these points at different times of the day, its currents are quite unlike those of any ordinary river. The water is full of whirlpools and eddies caused by a bottom of jagged peaks and huge potholes, some as much as fifty feet deep. And with the tides surging in and out of the narrow openings, the currents are swift, turbulent, and something very serious to contend with. Even with a favorable wind the great sailing ships of the day could make little headway against an outgoing East River tide and would often stand in considerable numbers in the bay, like small armadas, waiting for the tide to change.
“The extreme rise and fall,” Roebling explained, “is seven and a half feet. If the inflated caisson is just barely touching the ground at high water, it will press upon the base with a force of 4,000 tons at low tide, all of which has to be met by the strength of the shoe and the frames.” Not until the caisson was permanently “righted down” under several hundred tons of tower stone would this powerful, potentially destructive up-and-down action stop.
So he had Webb & Bell build in heavy truss frames of pine posts and stringers, with three-inch sheathing on each side and side braces to the roof every six feet. There were five of these inside partitions, each running the width of the caisson and dividing the interior into six separate chambers, each 28 by 102 feet. Once the caisson was in the water and resting on the bottom, doors would be cut in the partitions so the men could go back and forth from one chamber to another.
As the mammoth timber box grew on the ways, it looked like nothing ever seen before in an East River yard. Seven launchways were required (one for each of the outer edges, five under the interior partitions), and the total weight of the structure, by the time it was ready for launching, would be six million pounds, or three thousand tons, which was, for example, a thousand tons more than the Challenge, leviathan of the clipper ships built in East River yards. The caisson would contain some 110,000 cubic feet of timber and 230 tons of iron and it was being built to go down the ways in the usual fashion of a great ship, its long side toward the water. For the time being it stood fifty feet back from the ends of the ways, and as everyone who had had any experience with shipbuilding knew, the great danger of launching so large a mass was the chance that one end might get going faster than the other and the whole gigantic affair would wedge tight on the ways. It was also necessary of course that the caisson get up enough momentum coming down the ways to overcome the immense resistance offered by the water. So just getting the thing launched was an engineering problem of very major proportions. Indeed, Roebling said later that the problems of launching the caisson and of protecting it against sea worms caused him more anxiety than the prospect of sinking it.
As might be expected, all such questions and the steady progress of construction were of enormous interest to innumerable bystanders. Day after day people came down to the yards at the foot of Noble Street to take a look for themselves, even after the first snows arrived. Newspapermen and some of Tweed’s people came over from New York, as well as a number of engineers, not the least of whom was Captain Eads from St. Louis, whose own caisson was being sunk beneath the Mississippi by this time and who happened to be in New York on some other matter.
So concerned were the Webb & Bell people over the problems involved, so different was this job from any they had ever handled in all their previous experience, that they had insisted on being paid in advance—$100,274.51.
Once the caisson was in the water, the plan was to tow it downriver. How seaworthy it would prove to be in the turbulent current was another open question. After giving the caisson a thorough inspection, James B. Eads told Roebling he could expect trouble and said it might topple over if he inflated it during the trip downstream, which was exactly Roebling’s intention.
In the meantime, however, the waterfront had to be cleared at the point where the caisson would be docked and the riverbed had to be dredged deep enough for the huge structure to be floated into place. The clearing of the site began on Monday, January 3, 1870, and because the winter turned out to be abnormally mild, the work there, like the work at the shipyard, moved along faster than expected. Any other winter it would have been impossible to do much of anything.
Clearing the site took about a month. For daily commuters on the Fulton Ferry it all provided an interesting show and the first real sign they had had that the bridge was actually under way. About half of one big ferry pier had to be dismantled, fender sheathing torn out, massive stone-filled cribbing removed, and all without disrupting ferry service. An enormous steam crane, called the “Ox,” was brought in on a barge to pull out the old piles, and as they came up one after another, there was much amazement over the toll the East River had exacted. Each one was infested with thousands of sea worms in the area between the low-water mark and the mud line. As Roebling noted, “A pile which was sixteen inches in diameter below the mud, perfectly sound and free from worms, would be found eaten away to a thin stem of three inches just above the mud, and all timber was affected alike.” Then so that no one missed the point, he added, “This shows the necessity of going below the top of the riverbed with our timber foundation, and also proves its entire safety in that position.”
Once the old dockwork was out of the way, a large basin was to be built to contain the caisson, open toward the river but bounded on three sides with new piling. Within this area the riverbed was to be dredged to a uniform depth of eighteen feet at high tide, or deep enough to keep the caisson afloat at all stages of the tide. The dredges made great headway at first, as long as there was only surface mud to contend with, but then they hit hardpan and boulders. “The character of this material was next to solid rock,” Roebling wrote. The dredges could make but the slightest impression upon it. “Recourse was necessarily had to powder,” and the blasting commenced at night, from about seven in the evening until daylight, when traffic was light on the river and few people were about the ferry slip. Holes were driven into the river bottom with steel-headed iron piles. Then blasting charges were packed into iron canisters and dropped into the holes by professional divers. When the divers were out of the way and the pile drivers hauled back to a safe distance, the charges were set off by electricity.
Three pile drivers were kept in action, and with a little practice the men had the work down to a neat system, setting off some thirty-five blasts every ten-hour shift. During the day the dredges moved in and cleared out the results of the night’s work.
A number of the boulders encountered were too large to be picked up by a dredge and had to be dragged clear—the divers assisting underwater. The whole process was about six times as expensive as normal dredging, but still quite effective, and it provided valuable knowledge of the ground the caisson would have to penetrate. On one side, for example, near the new piling, a dozen blows of the pile driver would sink an iron pile forty feet through soft clay, but in the center area it took a hundred blows to go three feet. Toward the ferry the clay gave way to boulders of all sizes, closely packed, with coarse sand in between, and at the open end of the basin, on the river side, all soft strata had been washed away, leaving hardpan.
As time passed, Roebling decided to concentrate the dredging along the lines of the caisson’s edges and frames; the parts in between could be removed later, he said, from inside the caisson. He also had two holes blasted to an extra depth to accommodate the water shafts.
The work went slowly now, and while the blasting and dredging provided valuable knowledge of the riverbed, that knowledge itself was a most sobering reminder of the magnitude of what they were undertaking. To sink a wooden box as big as a fair-sized railroad station straight down through such material, and underwater, keeping the thing absolutely level the whole time, and bringing it to rest finally—perhaps fifty feet down—and at the exact spot it was meant to be, was a very tall order indeed. And added to that, along toward the end of January, reports began coming in from St. Louis of a strange malady among the men working inside the Eads caisson.
James Buchanan Eads was an authentic American genius and one of the looming figures of the nineteenth century. Slim, leathery, highly opinionated, disliked by many, he had survived an extraordinary life on the Mississippi that had included a lucrative underwater salvage business, a financially disastrous attempt at glass manufacturing, and the building of a fleet of ironclad gunboats during the Civil War. These slow, squat, ugly warships, built before the Monitor or the Merrimac and nicknamed “the Turtles,” had played a decisive part in defeating the Confederates on the Mississippi, along with the rams built by Charles Ellet. Eads had not designed the ships himself, nor had he gone into battle with them as Ellet had with his rams, but he had organized everything, having timber cut in Minnesota and Michigan, iron armor rolled at St. Louis and Louisville, keeping four thousand men at work on a night-and-day basis, and financing much of the operation out of his own pocket. At the time Washington Roebling was distinguishing himself on Little Round Top, Eads’s gunboats were assisting Grant in the successful siege of Vicksburg.
In early 1870 Eads was approaching fifty. He was the sort of person who liked to play chess with two or three others at a time, and in a recent weight-lifting contest among some of his blacksmiths, he had come in second.
During his years in the salvage business Eads had worked with diving bells up and down the Mississippi and was said to know more than any man alive about the river’s treacherous currents and the character of its bottom. This had been an important factor when he presented St. Louis and New York financial backers with his radical proposal for a bridge over the Mississippi. But it was his unbridled self-confidence and his reputation as a man who could get things done that mattered most in the end. He managed to convince men who had worked with the country’s foremost engineers that he, James B. Eads, was the one man fit to bridge the Mississippi at St. Louis, that the bridge he wanted to build was the only answer, and this despite the very well-known facts that he had had no formal training as an engineer and that he had never once built a bridge before. Both Charles Ellet and John A. Roebling had prepared plans for suspension bridges at St. Louis back in the 1850’s. Later, the year before he died, Roebling had done an entirely new set of plans, combining both suspension cables and parabolic arches. But Ellet’s and Roebling’s ideas had been turned down. (The St. Louis people were fools, John Roebling wrote to his son.) Now Eads and his bridge were the talk of St. Louis.
The great need was for a bridge to carry a railroad and highway over the river without interfering with steamboat traffic. The Mississippi at St. Louis is about the same width as the East River. Instead of a heavy iron truss, the customary thing then for railroad crossings, or a suspension bridge, Eads had conceived a mammoth arched bridge, with arches of steel set on stone piers. He intended to span the river with just three of his steel arches, the biggest of which, the center span, would be longer than any arch of the time by several hundred feet. To avoid interfering with river traffic during construction, his assistant, an engineer named Henry Flad, had devised a cantilever system nobody had tried before. The halves of each arch would be built out toward one another from their respective stone foundations, like great jaws slowly closing over the river, which was the conventional way, except that here the temporary supports needed (until the jaws joined) would be supplied from above. The usual practice was to prop such arches up from below with temporary timber “falsework” that could be torn out once the bridge was finished. But since this would be impossible, obviously, if the river was to be kept clear, Eads would hang the arches from overhead cables attached to temporary wooden towers built above each of his stone piers.
So the design of the bridge, the material he intended to build it with, the way he planned to build it, just about everything about the bridge, was unorthodox and untried. And when he had first proposed it, Andrew Carnegie had decided that somebody who knew about things mechanical, as he said, had better look over the plans.
Carnegie’s interest in the bridge was twofold. He had been approached by Eads’s St. Louis backers to see if he might be interested in selling some of their bridge bonds. Also, it was a few years before this that he had organized his Keystone Bridge Company, one of the first to specialize in manufacturing iron railroad bridges. Carnegie enjoyed talking about his love of bridges. Like Thomas Pope and John Roebling he saw them, he said, as testimonials to the national spirit and professed great personal satisfaction in the part he played in building them.
The Keystone company was now being invited to come in on the St. Louis job as consultants and to handle the superstructure. So Carnegie, quite sensibly, asked for an opinion on the bridge from Keystone’s chief engineer and president, J. H. Linville, whom Carnegie described with customary enthusiasm as “the one man in the United States who knew the subject best.” This was an overstatement, but Linville was certainly among the finest men in engineering. He had been bridge engineer for the Pennsylvania Railroad before Carnegie hired him and the huge iron truss he had built over the Ohio at Steubenville in 1864 was considered the outstanding structure of its kind.
Linville asked that a set of Eads’s plans be sent to him. He examined them carefully, then, a little like the paleontologists who had been asked to give an opinion on the Cardiff Giant, he solemnly declared the subject preposterous. “The bridge if built upon these plans will not stand up; it will not carry its own weight,” he told Carnegie in private, and presently, in a formal statement, he called the bridge “entirely unsafe and impracticable” and said any association with it on his own part would imperil his reputation and was therefore out of the question.
Linville was quite wrong and Carnegie, who knew nothing about engineering, urged Linville to lead Eads “into the straight path.” Eads, however, was not about to be dissuaded or to have any outsider, regardless of reputation or connections, begin doctoring his bridge. In the end he would convince even Linville that he knew what he was doing. The Keystone company went to work on the bridge; Carnegie went off to London to sell a block of bonds to the American financier Junius Morgan, father of J. P. Morgan; and by the summer of 1867 Eads was confidently proceeding with the preparatory work for the first abutment beside the St. Louis waterfront. In neighboring saloons it was said that the bridge would take seven million dollars to build—and seven million years.
As things turned out the final cost would come to something near ten million, and seven years would go by before the job was completed. Once in use the bridge would be acclaimed by everyone, and by engineers especially. As one engineering historian would write, the bridge was “an achievement out of all proportion to its size,” something Washington Roebling thoroughly appreciated at the time Eads came over to visit the Webb & Bell yards.
Like every bridge engineer and every railroad official in the country, Roebling was keenly interested in the St. Louis bridge, but since Eads, along with everything else in his radical scheme, also planned to sink his piers by means of pneumatic caissons, Roebling perhaps more than anyone appreciated the full daring of the man and the tremendous importance of what he was attempting, not just to his own work at Brooklyn but to the whole future of bridge engineering.
When he first envisioned his bridge, Eads had originally planned to use coffer-dams to sink the two midriver stone piers upon which his great steel arches were to rest. But in April of 1869, he had returned from a trip to Europe, convinced he had a better answer. He had seen the French engineer Moreaux use a pneumatic caisson to sink piers for a bridge over the Allier River at Vichy and he came home full of faith in the technique and sure he could make it work at St. Louis, even though the Mississippi, as he knew better than anyone, was not the gentle Allier.
So through that summer of 1869 Eads and Roebling had been devising their own separate plans for the foundations of the two biggest, most important bridges of the age, each man working quite independently and with only his own judgment to go by. Eads, however, had his caisson in the water by mid-October, before the contract with Webb & Bell had even been signed, and by the time Eads arrived in Brooklyn, his caisson was already well on its way into the sandy bed of the Missssippi.
Of the two, Roebling was unquestionably the better educated on the development of caissons in Europe and the various ways they had been used. Eads had happened onto the technique almost by chance and took about the least time possible to educate himself. Roebling’s father had incorporated caissons in his plans from the start, knew much on the subject, and Roebling himself had taken great pains in his studies, spending close to a year in Europe for that specific purpose. Furthermore, unlike Eads, Roebling was a trained, experienced bridge engineer and was fluent in both French and German. Eads, who spoke only English, had had a difficult time conversing with some of the European engineers he met.
Still and all, Roebling doubtless appreciated that Eads was a man with a most uncommon gift for solving problems, a man of extraordinary originality and determination, a man, in fact, very much like his own father. Roebling also knew that what Eads was up against at St. Louis was far closer to his own situation in Brooklyn than anything the Europeans or McAlpine or anyone else had ever had to cope with. And most important, Eads, unlike Roebling, now had some working experience with caissons.
The caisson Eads had in operation was only about one-third the size of what Roebling was having built in Brooklyn, still it was bigger than any used by the Europeans. More significantly, by January 1870, the Eads caisson was already as deep as Roebling expected he would have to go on the Brooklyn side, and it was still descending steadily through Mississippi sand and mud that offered almost no resistance. By the end of January the trouble had begun.
From the very first Eads’s men had noticed certain peculiarities about working in the heavy atmosphere of the caisson. The most manly voices had a thin girlish sound, for example. It was impossible to whistle or to blow out a candle, as the men gladly demonstrated for the many visitors Eads liked to bring down. Some of the men mentioned a notable increase in their appetites. Others talked of trouble breathing or of a painful ringing in the ears. But by the time they were down forty feet there had been several clear cases of the mysterious sickness, a subject Eads and Roebling had both heard something about in Europe.
As early as 1664 an English doctor named Henshaw had published an essay proposing, ironically enough, that compressed air be used as a method of treating a variety of common disorders. In France and Germany, institutions sprang up offering the latest facilities for just such atmospheric treatment. Compressed-air “baths” were claimed to work miraculous cures and became something of a fashion, and particularly for curing indigestion. But the pressure in such baths was never much greater than normal.
The first civil engineer to work with compressed air of any substantial magnitude, however, was a Frenchman named Triger, who in 1839, or thirty years before Eads and Roebling built their caissons, used compressed air inside an iron tube to hold back water while sinking a mine shaft through quicksand. The technique had worked quite successfully, but before the job was completed, Triger observed a number of unexplainable reactions among his men and put down in his notes what are thought to be the earliest recorded cases of caisson disease, or “the bends.” Two of his men, Triger wrote, had been hit quite mysteriously by sudden sharp pains in the arms and knees about half an hour after coming out into the open air.
Later in France there would be more serious cases. Men would be seized at home, long after coming out of compression. Sometimes the pain was accompanied by chills and vomiting. Other symptoms were recorded: a great dullness of mind, an incoherence of speech or stammering, nosebleeds, a distressing itching of the skin, tottering gait, an increased flow of urine, even pain in the teeth. One supposedly scientific study noted that Hungarians and French suffered least, while Italians, Germans, and Slavonians were said to have had by far the worst time. It was also known for a fact that one or two men had died of the experience.
The first signs among Eads’s men had been occasional muscular paralysis in the legs. But there was no pain connected with it, the men said, and the sensation passed off in a day or so. But as the caisson went deeper more and more of them began having trouble. In some cases now the arms were affected, as well as the bowels and sphincter muscles. Men complained of severely painful joints and sudden, excruciating stomach cramps. Still, nine out of ten of those affected felt no pain whatever, they said, and so long as the phenomenon remained painless, it would not be taken very seriously. Indeed, according to one account, “A workman walking about with difficult step and a slight stoop was at first regarded as a fit object for jokes, and cases of paralysis and cramp soon became known popularly by the name of ‘Grecian Bend.’”
To ward off trouble the men rubbed themselves with an “Abolition Oil” that was said to work like a charm. Some of them began wearing bands of zinc and silver about their wrists, arms, and ankles, and such were the claims of success that Eads decided to thus outfit every man on the force at the company’s expense, only now the protective armor, as the men called it, was worn about the waist as well, and even under the soles of the feet. Still instances of the unaccountable malady continued to increase.
When one of his foremen got sick, Eads decided to shorten the shifts inside the caisson. The men would stay down for four hours only, then rest for eight hours before going back for another four. The caisson was at forty-two feet by then. By February 5, when it was at sixty-five feet, Eads again altered the schedule, to three two-hour shifts, with rests of two hours in between, none of which was very popular with the men, since with every change of the shift they had to make a long climb out of the caisson, up a spiral stairway. For those who felt no adverse reaction from the compressed air, the new routine was just one more big inconvenience, while for those who did, the climb was only added torture. As the official history of the bridge states dryly, “The fatigue of ascent added not a little to the distress and prostration of those affected with cramp.” At seventy feet, on February 15, with the air pressure in the chamber at thirty-two pounds per square inch, or more than double that of normal atmospheric pressure, one man was in such pain that he was sent to the hospital.
Severe cases grew a lot more common after that. One man became unconscious and did not speak for three hours. Nobody considered the thing a joke any longer. But even so, as Eads would tell visitors, many of his men, the majority in fact, had been affected in no way at all. He had taken hundreds of visitors down into the caisson, even “delicate ladies,” he said, without any of them experiencing ill effects. There was no doctor who could explain it satisfactorily for him. Some doctors said a slower transition from the abnormal to natural pressure would prove less injurious; others claimed the contrary, that the trouble came from passing too rapidly from natural into compressed air. But Eads argued that neither could be correct since none of his air-lock attendants had been hit. It was the amount of time spent under compression that caused the trouble, he maintained, plus the general physical condition of the individual.
He pointed out that most of the men who had been struck down were new hands, unaccustomed to the work, that they had been thinly clothed and poorly fed to begin with, or, in some cases, alcoholic. So as the caisson continued its descent, Eads ordered that only men in prime physical shape be hired for the work.
Then on Saturday, March 19, which happened to be the same morning the Brooklyn caisson was launched, Eads reported the first death. The man’s name was James Riley. He had worked the first shift, just two hours in the chamber, came up feeling fine so far as anyone knew, then fifteen minutes later gasped for breath and fell over on his face. He was the first American to die of the mysterious disease. But at least fifteen more would die at St. Louis before Eads finished his bridge, and more would be crippled for life.
About three thousand people turned out to watch the launching of the Brooklyn caisson. The Kings County Democrats, to no one’s surprise, took the opportunity to make it a day of speeches and band music. People had trouble thinking of a suitable way to describe the main attraction, but most eventually concurred that it looked “more like a huge war leviathan or battery for harbor defense than any other thing.” And as the Eagle observed, a very large number of them had turned out chiefly because they doubted it could ever be launched.
The top, or deck, of the caisson was strewed with tackle and various odd-looking pieces of machinery. A number of lines were connected to a steamboat standing by in case of trouble going down the ways, and at the rear of each way, heavy wooden rams had been rigged, to be worked simultaneously, to get the huge structure started. Inside, a temporary airtight compartment had been built on the forward wall to buoy up that side as it hit the water, and a full complement of crabs, winches, and 150 wheelbarrows had been stowed away, battened down with strips of wood.
The launch took place at ten thirty and was in every respect a great success. As soon as the last block was split out, the giant mass began to move. It went down straight and even, with no need of assistance. It struck the river with just enough speed to overcome the resistance of the water and the air chamber worked to perfection, keeping the front side from sinking. The deck never even got wet.
A great roar went up from the crowd. An air pump on the deck was at once set in motion and in a few hours the water was all out of the work chambers, thus proving to Roebling’s satisfaction that the thing was airtight. Later on the air inside was allowed to escape and the top of the caisson settled to within seventeen inches of the water, which, Roebling noted with pleasure, happened to agree exactly with his previous calculations.
But the difficult work of dredging the site for the caisson was running far behind schedule. It would be another month before everything was ready there and nothing much could be done to speed things up. So apparently Roebling decided this would be an excellent time for him to go to St. Louis and see how Eads was progressing. The Bridge Company agreed and funds were provided for Horatio Allen to go along too.
Eads had a regular routine for handling visitors and it appears that Roebling and Allen received the same treatment when they arrived in St. Louis in early April. Eads would go over the plans first, explaining things, then set out in a tender to the spot mid-river where a flotilla of barges and derricks hovered over his submerged caisson. The functions of the various workboats would be described, after which Eads would lead his guests down the narrow spiral stairway, through the air lock, and into the caisson proper.
Roebling, as he would write later, had the highest admiration and respect for Eads and “his remarkable inventive talent.” Roebling also said later that Eads was extremely courteous to him during his two days in St. Louis and one man who was on hand at the time, a friend of Eads’s, said Eads took special pains to explain each and every detail to the younger engineer. So if there was any friction between them at this point in the story, there is no evidence of it.
Roebling appears to have returned to Brooklyn confident he was proceeding along the best possible course, and although he must have heard a great deal about the caisson sickness in St. Louis, most of those he talked to, including Eads, were convinced that whether a man got hit or not was largely a matter of luck and to judge from things he said later Roebling had arrived at about the same conclusion. Certainly Eads then knew no more than Roebling did about how to prevent the trouble, or how to cure it, as must have been obvious to both of them. Men were still suffering, more of them were dying.
Eads would keep plunging ahead with his work, sure that solutions could be improvised somehow should the problem grow still worse. In his place Roebling probably would have done the same. The great tragedy was that both of them were almost totally ignorant of what others had already learned about the effects of compressed air. They were both unaware, for example, that the surest, fastest remedy for caisson sickness was already known.
Possibly things might have gone differently for each of them had they compared notes as time went on, or had they been in touch with the few others there were working on similar problems. But they were living in an age when communication among professional colleagues was, by later standards, frequently at the most superficial level. Engineering then, like nearly every other line of work, was intensely competitive. An organization such as the American Society of Civil Engineers was striving with some success to encourage an open exchange of professional information and there were several reputable journals publishing valuable technical material. Still there was as yet no strong tradition along these lines and in some quarters not even an inclination. The railroads, the biggest clients for engineering talent, as well as the training ground for a very large number of engineers, were not the sort of institutions to foster an open exchange of valuable ideas. Minding one’s own business was considered among the basic rules of business. There were trade secrets in other words, and the sharp rivalry men had to live with frequently gave rise to the worst kinds of professional jealousies and animosity. Roebling’s own father, for example, had once written to Charles Swan to warn him not to hire a certain man simply because he had once worked for Ellet. “I do not want any news carried between myself and Mr. Ellet,” John Roebling had said.
There were exceptions, to be sure, but even then, often as not, it was because the party sharing his special knowledge stood to gain financially thereby. Carnegie had so agreeably granted Eads the benefit of Linville’s experience only when a large contract for the Keystone Bridge Company was involved. Eads’s own first instructions on caissons had been given by the French bridgebuilder Moreaux largely because Moreaux happened to be chief engineer for a leading French ironworks that, like the Keystone company, wanted to do the superstructure for Eads’s bridge.
Perhaps, after Roebling returned to Brooklyn, he and Eads simply felt they had little more to say to each other, or little to gain by saying more than they already had. Or possibly for all their courtesies, things did indeed go sour at the start, simply on personal grounds. Eads, after all, was an exceedingly proud person who knew most all the answers always and was forever on his guard with anyone who might try to prove otherwise. He viewed his bridge, and none other, as the single most important engineering event of the century. Roebling almost certainly felt the same about the bridge he was about to build but, unlike his father, never once would he say so. Quite possibly Eads considered Roebling a threat and he was not about to stand in the shadow of any man. Maybe he simply saw Roebling as a nuisance.
It is also understandable that a man who had achieved so much on his own, against all odds and despite the doubters, might be reluctant to go out of his way to help a young man who appeared to have been handed quite enough already, and who so far had done little to prove himself particularly worthy of all that. Furthermore, Eads at best was a difficult person. *
But on top of everything else there was the prevailing belief of the time that a stiff spirit of independence was in itself a very good thing. And both Eads and Roebling were exactly the sort of men others would have pointed to as shining examples.
So they would each go their own way, alone, set apart by half a continent and, in time, open hostility.
On May 3, in the early afternoon, the Brooklyn caisson made its maiden voyage, which, of course, was also its final voyage—four miles down the East River to the site beside the Fulton Ferry slip. The chambers were again fully inflated, the air pumps were kept running, and the gigantic box was now riding with its deck a full nine feet above the water. (This inflation was essential, since in one part of the river there would be only a foot of space between the river bottom and the lower edge of the caisson.) Half a dozen tugboats took it in tow and proceeded out into the current at about quarter to two, “creating a great sensation among all whose good fortune led them to view one of the wonders of the nineteenth century,” which was so soon to be “hidden from the gaze of mortal eyes.”
Roebling, Kingsley, Horatio Allen, Bell of Webb & Bell, and three or four others went along for the ride, standing forward on the long, flat deck. And any doubts Eads may have planted about the caisson staying afloat were quickly forgotten. In the words of one witness, it came down the river “as placidly as a swan upon the bosom of an inland lake.”
They tied up a block above Fulton Street, and by the time the sun went down, several thousand people had given it their personal inspection. “Of course, everyone was anxious to be able to say in future years that they had been upon the monster,” wrote the Eagle. The monster, it seems, appeared even more formidable than anyone had expected and especially on toward dusk.
The following morning, at the turn of the tide, the caisson was shifted into position inside the new basin, the whole operation taking little more than an hour. As the crowded ferries churned in and out of the slip next door, young men were seen climbing to the tops of the cabins for a better look.
For the next several weeks additional courses of timber were built on the roof, each course at right angles to the other, with spaces left between the timbers, which were filled in with concrete to add weight and to help preserve the wood. Additional sections for the water shafts, air locks, and supply shafts were also installed as the roof grew in size. And on May 10, Roebling, Colonel Paine, and Francis Collingwood made the first inspection below. The temporary air compartment put in for the launching was removed, two doorways were cut through each of the interior walls, and any loose rock or mud under the edges was shoved out. A few men complained of trouble breathing the heavy air and apparently there was a sharp change in temperature inside the air lock every time the pressure changed, about which something would have to be done. The heat was up over 100 degrees. But otherwise everything was going as expected.
In his report to the directors of the Bridge Company, signed June 12, Roebling wrote:
For three weeks past a gang of forty men have been at work in the caisson for eight hours every day, under the charge of Mr. Young, principally in leveling off and removing boulders which happened to lie under the frames and the edges. A deposit of dock mud, from two to three feet deep, has made this work exceptionally unpleasant. The dredges, which are now beginning to work, will remove it in short time. The removal of large stones from under the shoe, some of them 100 cubic feet, is a matter requiring considerable skill and perseverance.
During all this time the caisson was rising with every high tide, then resting on the bottom again at low tide, which, of course, meant that work within could be carried on only during the low-tide time of day, when the chambers were comparatively free from water.
As more timber courses were added on top and the over-all height of the caisson was increased by a full ten feet, its center of gravity was raised considerably, causing a condition of “unstable equilibrium”—that is, the caisson would no longer rise uniformly with the rise of the tide. One end would come up ahead of the other and this would cause what was known as a blowout, a phenomenon of imposing appearance, as Roebling said, and the subject of much excited talk in Brooklyn.
As the tide was rising, and the downward weight of the caisson was being overcome by the increased tension of the air inside, along with the buoyancy of the river outside, one end of the caisson would suddenly tip up six inches or more. For an instant the tension of the air inside exceeded the head of water outside, and there would be a huge rush of air from beneath the shoe, carrying with it a column of water weighing hundreds of tons to a height of maybe sixty feet. Fish would fall all over the top of the caisson and the men working there would scramble to gather them up.
For the men inside the caisson such occurrences were quite terrifying at first, but of little serious consequence. There would be a terrific roaring noise and a sudden blast of air, both of which were decidedly unsettling, but after it had happened two or three times the men grew accustomed to it and the loss of a few hundred tons of air from a volume so large (163,000 cubic feet) was nothing to worry about especially.
Seen from the shore or the ferry, however, the sudden appearance of a waterspout on the East River was a spectacle that would be talked about for years by all who saw it.
It took three courses of stone and most of June before the vast wooden box was bobbing up and down no longer and was grounded on the bottom to stay. The first stone to be placed on top, the cornerstone as it were, was a block of blue limestone from the Kingston quarry, three feet by eight, weighing 5,800 pounds. There was no particular ceremony that went with it and so far as is known nothing was carved on it.
A stoneyard, as it was called, had been established downriver, below the Atlantic Docks, near Red Hook, and four huge scows had been especially built to bring the stone up to the site. McNulty had been put in charge of laying the first courses and the work had gone much slower than normal since portable derricks had to be used to move massive blocks, weighing anywhere from two thousand to three thousand pounds apiece. But once the caisson was righted down, three permanent derricks were mounted directly on top of it. They had great wooden masts fifty feet high, like the masts of a ship, and booms that were capable of swinging to any point on the deck.
By now, too, six big air compressors, built by the Burleigh Rock Drill Company, of Fitchburg, Massachusetts, were in operation inside a long shed nearby in the yard. Each had a twenty-horsepower steam engine driving two single-acting air cylinders of fourteen-inch stroke and fifteen-inch diameter. Each engine had its own boiler and they were all so connected that the stopping or breaking down of one boiler or engine would not affect the others. All piping and connections were in good order and working properly. (A ten-inch main took the compressed air underground some 150 feet to the caisson, where two six-inch rubber hoses carried the air down the supply shafts to the work chambers.) Thomas Douglas, a mason who had done the finest stonework in Prospect Park, had been put in charge of the labor outside the caisson, while the foreman inside was a strapping man named Charles Young.
To date everything had gone exactly as planned. There had been no serious interruptions. Material had arrived on time. All necessary machinery had been purchased and installed. Proper offices had by now been established for the Bridge Company in the UnionBuilding on Fulton Street, which was only a short walk from the Fulton Ferry. Everyone involved was to be congratulated, wrote General Superintendent William Kingsley in his own first official report.
The great caisson could now begin its descent.