Under Pressure
AT THE MIDDLE OF THE NINETEENTH CENTURY , St. Louis, Missouri, was a city on the move, America’s burgeoning frontier metropolis. By 1860 the city had 160,000 residents, and if the bustling riverfront wharves gave any indication, growth and prosperity were not about to end. Standing at the confluence of the vast Mississippi and Missouri river networks, St. Louis tapped the wealth of nearly the entire continent, from the Appalachians to the Rockies and from the Great Lakes to the Gulf of Mexico. By the 1860s, however, the surging might of the railroads was beginning to erode the importance of river traffic. St. Louisans watched with concern as train lines spread in the East and pushed westward through Chicago. The Mississippi River, long the city’s highway and source of abundance, had suddenly become a barrier, blocking access to the economic innovation of the age: fast and reliable rail transit.
The solution, of course, was to bridge the river, but this was no simple task. First there was a political battle to wage. Proposals for a span at St. Louis had been circulating since the 1840s, and each one had raised the wrath of the most powerful and wealthy segment of St. Louis society—the steamboat men, who knew that a bridge would destroy their monopoly. Second, there were big engineering questions. The bridges of the day collapsed with appalling regularity, and a span at St. Louis would be among the longest in the world.
By the close of the Civil War it seemed that these hurdles might be overcome. While many steamboat men remained disgruntled, others were beginning to understand the necessity for a bridge and figured that railroading might be a good business to look into after all. Steamboat money was included in the small circle of wealthy men who formed the St. Louis and Illinois Bridge Company in 1864. They spent two years gaining government approvals, raising money, and making plans. Although the scientific complications of building the span remained, prospects seemed brighter when a local genius named James Eads joined the company as chief engineer in early 1867.
JAMES BUCHANAN EADS WAS THE very model of a self-made man. Though he had no schooling beyond the age of thirteen, he had undertaken years of self-education. While clerking in a dry goods store and later working as a clerk on a Mississippi steamer, he read voraciously. In the early 1840s Eads designed a diving bell to salvage sunken river cargo and earned a fortune recovering wrecks. When the Civil War broke out, he won a government contract to build ironclad gunboats to help secure the Mississippi. (See “Eads and the Navy of the Mississippi,” Invention & Technology , Spring 1994.) The ironclads were responsible for many crucial Union victories.
Despite his varied and successful career, the forty-six-year-old Eads had never built a bridge or received any formal engineering training when the company appointed him its chief engineer. Lacking experience, he substituted supreme confidence in the laws of nature and in James Eads. Rather than propose a conventional truss bridge, he designed a crossing that in its final form was nothing less than radical: He would span the Mississippi in three great arches of more than 500 feet each. And they would be built with large amounts of steel, a material never before used extensively in any bridge. To hold up his arches, Eads planned two stately granite-and-limestone river piers, rising 80 feet above the Mississippi at high water and matched by a pair of shoreline abutments. Upon these structures he would place two decks; the lower, running along the arch crowns, would carry two lines of railroad track, while 21 feet above, the top deck would provide a roadway for vehicles and walkways for pedestrians.
Jacob H. Linville, a professional engineer and a respected authority on bridge construction, looked over the design and predicted failure: “The bridge if built upon these plans will not stand up; it will not carry its own weight.” A convention of bridge engineers, meeting at St. Louis in the summer of 1867 at the behest of a rival promoter, expressed similar caution, recommending spans of no more than 350 feet and concluding that the “necessities of the case” did not require arches “of such great length for which there is no engineering precedent.”
Nonsense, Eads replied. “Because a thing has never been done,” he asked, why believe it impossible “when our knowledge and judgment assure us it is entire practicable”? During construction, when opponents said his three 500-foot arches would surely collapse, Eads told a friend that if “this were my own enterprise, and if my own fortunes alone were at stake, I would have bridged yonder river with a single arch fifteen hundred feet in length.”
Confidence should not be confused with contempt, for Eads deeply respected the Mississippi. The river was merciless, annually breaching levees, erasing islands, and carving new channels. Any bridge that attempted to outwit the Mississippi, Eads knew, would ultimately be swallowed by it. This respect led Eads into fundamental disagreement with his brother engineers, who proposed much simpler plans for the St. Louis crossing. At the heart of the dispute were the piers that would support the span. Other engineers argued that piers could be built upon wooden and metal pilings driven deep into the riverbed—a proven method, conventional and economical. From the start, however, Eads insisted that the granite-and-limestone piers be founded upon nothing less permanent than the bedrock underlying the Mississippi.
Eads backed his argument with rare firsthand knowledge. Few other men had stood and worked upon the bed of the Mississippi, as he had during his years in salvage. “I had occasion to examine the bottom of the Mississippi, below Cairo, during the flood of 1851,” Eads told the company, “and at 65 feet below the surface I found the bed of the river, for at least three feet in depth, a moving mass, and so unstable that, in endeavoring to find a footing on it beneath my bell, my feet penetrated through it until I could feel, although standing erect, the sand rushing past my hands, driven by a current apparently as rapid as that at the surface.” The Mississippi riverbed was a creeping pack of sand, slowly moving southward and constantly in flux, varying in depth and stability with the seasons. When obstructions or low water slowed the current, the stream deposited sand and the riverbed grew in depth. When rains or snowmelts increased its velocity, the water carried a greater load of sand, scouring away the river bottom. Fluctuations in depth of a dozen feet or more were not uncommon, and at St. Louis, where a narrow channel increased the stream’s speed, Eads once recorded a change of 41 feet.
Besides being narrow, the riverbed at St. Louis is unusual for its immense depth. The bedrock upon which Eads so confidently planned to build sat more than 100 feet below the surface of the Mississippi, covered by roughly 25 feet of water and 80 feet of sand. No bridge piers had ever required foundations anywhere near so deep, and to attempt the task in the middle of the rushing Mississippi, Eads’s critics asserted, was a risky, expensive, and probably entirely needless proposition. Surely, they reasoned, it would be possible to lay solid foundations within so deep a riverbed. Eads countered that a Mississippi bridge built on a conventional piling foundation could be swept downstream with that riverbed.
Although he was certain about the need to reach bedrock, Eads did not know at first exactly how he would get there. According to geological borings, the Mississippi bedrock steadily fell away eastward from the Missouri shore, dropping from about 50 feet below the high-water mark at St. Louis to nearly 130 feet on the Illinois side. While many engineers could have managed the shallow dig near the Missouri shore, the mid-river excavations of 100 feet or more were another matter entirely. At first Eads planned to dig within enormous oval cofferdams, metal enclosures anchored in the river within which excavation and construction work could proceed isolated from the surrounding waters. The bridge’s west abutment, which required the shallowest excavation (a mere 47 feet, though the dig was obstructed by a layer of abandoned steamboats and other junk), was built this way, starting in August 1867. During a trip to Europe early in 1869, however, Eads observed and studied the workings of the “plenum pneumatic” method of using large underwater diving bells, or “caissons.” He returned to St. Louis excited about a new plan, which, like almost everything else connected with his bridge, he promised to execute on a scale more massive than anyone else had ever attempted.
The European caissons were woodand-iron boxes, big enough for men to work inside, built with reinforced walls and roofs but no floors. A caisson was first floated on the river, open end down, and then submerged by cementing masonry onto its roof. At the same time, pumps filled the caisson with compressed air, which helped support the masonry and expelled water so that men could work inside. Once the caisson rested on the riverbed, workers entered through an air lock and began removing the sand, mud, and rocks beneath them. As the men excavated, the caisson slowly sank into the riverbed, and further layers of masonry were added on top. This process of digging below and building above continued until the caisson found stable footing. Finally, the work chamber was filled with cement, and the pier was solid. Thus the caisson itself eventually became the pier. The procedure would be faster and cheaper than using cofferdams.
Construction of the east-pier caisson began in the spring of 1869. It was built in the form of an irregular hexagon, with two parallel sides 52 feet long and four shorter ones of 33 feet 6½ inches. The total length was 82 feet, the width 60 feet, and the height 9 feet. Riveted iron plating covered the entire outside surface, ¾ inch thick on the sides and ½ inch thick on top. The roof was further braced by thirteen iron girders, each 5 feet high, bolted in parallel lines on the caisson’s top. Inside, two great walls of oak divided the work chamber into three separate rooms of roughly equal size. Within these rooms, projecting from the ceiling, were seven cylindrical iron tanks—the air locks—the largest of them 6 feet in diameter and 6 feet high. A 3-inch-thick iron blade ran along the bottom of the six walls, protruding 6 inches below the caisson. This blade, called the cutting edge, would carry the weight of the caisson and pier masonry through the riverbed. When completed in the early fall, the east-pier caisson weighed a massive 437 tons.
Shortly before noon on October 17, 1869, the east-pier caisson was launched from a work yard south of the city. The next day it was towed upstream to St. Louis, positioned at the bridge site, and anchored into place by ten 80-foot pilings driven into the riverbed. Once secured, the caisson was flanked by pontoon boats along its eastern and western sides. These boats, which would remain in place until the pier was finished, housed the machinery that would power the construction: six steam boilers, two engines, twenty-four hydraulic jacks, several air pumps, and, mounted on their decks and extending over the top of the caisson, a 50-foot-high derrickand-pulley framework. Over the next days carpenters and riveters worked to close leaks in the plating, while ten 25-foot-long suspension screws, designed to guide the descent of the caisson until it hit the riverbed, were attached from the pontoons and pilings to the iron hull.
On October 25 air was pumped into the caisson, and its temporary wooden floor was removed. Workmen then started laying masonry on top, each course pushing the caisson a little deeper beneath the Mississippi. The undertaking proceeded fairly smoothly during the first weeks. Barges carrying limestone blocks as heavy as 7 tons moored alongside the pontoons; the hydraulic derrick-and-pulley system hoisted the stones onto the caisson; masons cemented the blocks into place; and engineers supervised the process and adjusted the suspension screws to keep the caisson level. On November 17, when workmen had laid 33 feet 7 inches of masonry, the southern end of the caisson hit sand, while the northern corner stood some four feet above the sloping riverbed. Five days later—a little less than a month after the sinking had commenced- the entire cutting edge except a portion of the northeast side rested in the Mississippi’s sandy bottom.
BY THE END OF NOVEMBER, WITH the cutting edge completely embedded in sand, work started inside the air chamber itself. Men began their shifts by descending a candlelit spiral stairwell in the center of the pier and squeezing through an oval hatch about 2 feet in diameter, the entrance to the air lock. The main air lock was a large iron canister, 6 feet in diameter and 6 feet high, typically used by eight to ten men at a time. Once they were inside and the outer door was secured, the lock tender would open a brass valve to let compressed air pass from the work chamber into the lock. Men exited by the reverse process.
Under normal conditions the earth’s atmosphere exerts a pressure of 14.7 pounds per square inch (psi). Air pressure within the caissons was measured in excess of that amount. During the first days of excavation, with the pier projecting only a few feet into the river bottom, pressure in the caisson was about 17 psi, slightly more than double atmospheric pressure. At this stage, passage through the air lock and into the caisson proceeded quickly—about two minutes, if the lock tender opened the pressure valve fully. The brief passage impressed, intrigued, and at times frightened the caisson workers. The iron lock was a damp, dark can with a “dismal, dungeon-look,” according to one account. When the brass valve was opened, compressed air rushed loudly into the lock, filling the chamber with a sharp, echoing hiss that continued until the atmosphere had been fully pressurized. As air flowed through the valve, the lock became markedly warmer. During depressurization the lock suddenly chilled.
The burst of pressure often gave lock passengers earaches, which workmen could partially relieve by blowing their noses. Swallowing also helped, so Eads placed a pail of water and a drinking cup in the lock. As the caisson sank deeper and the pressure increased, however, the pain was sometimes so great that men trying to enter the caisson had to give up and go back. In other cases the atmospheric fluctuation left passengers with bloody noses.
Once the lock was fully pressurized, the oval door leading into the work chamber opened freely, swinging of its own accord. Though the caisson was not as dark as the air lock, candles inside glowed with dark, dull flames, burning quickly in the pressurized air. Ventilation was very poor, and the place acquired a uniquely thick atmosphere, a mixture of humidity, smoke, and sweat. The temperature within the caisson remained comfortable, typically between 45 and 50 degrees Fahrenheit through the winter and between 65 and 70 degrees by spring.
Although the temperature was mild, the labor was arduous. A workman’s day consisted of two 4-hour shifts, with two hours off in between. Compressed air held the waterline about a foot below the cutting edge, but the sand remained damp and heavy. Workers endlessly shoveled the moist sediment toward a water-powered sand pump invented by Eads. Approximately thirty men worked within the caisson at a time, directed by several foremen.
With masonry work, digging, and sand pumping continuing around the clock, the east caisson settled at a rate of up to 20 inches per day. The main delays encountered were due to late shipments of stone. Eads launched the west caisson on January 3, 1870. It measured 82 feet by 42 feet, somewhat smaller than its eastern sister, and contained only five air locks. Excavation at both piers proceeded rapidly through the winter.
As the two piers settled toward bedrock, their caissons required greater pressure inside to expel the water and support the masonry. And as the pressure rose, the time it took to pass through the locks steadily became longer. On February 12, for example, with the east caisson 71 feet below the waterline and pressure at 33 psi, a visiting party spent eleven minutes amid the hiss of pressurization, during which time the thermometer climbed from 47 to 62 degrees. Afterward, during the six-minute depressurization, the temperature dropped from 45 to 34 degrees. By mid-March, with pressure near 50 psi, depressurization would sometimes so chill the air lock that moisture froze and fell like snow. Eads, who often rushed through the lock with the stopcock fully open, once measured a depressurization drop of 32 degrees.
Although Eads’s initial schedule proved too ambitious—he thought he could have both piers on bedrock by the end of 1869—his progress was remarkable nonetheless. Sand pumping under the west pier commenced at the beginning of February 1870. Meanwhile the east caisson sat more than 60 feet below the waterline, with less than 30 feet of riverbed remaining, and Eads was confident of reaching bedrock by early March.
THE PROJECT WAS THE TALK of all St. Louis, and the work site became a very popular attraction. On the afternoon of February 8, 1870, for example, with the east caisson 66 feet below the surface, Eads invited a party of around twenty men and women to inspect a telegraph that had been installed in the air chamber earlier that day. After transporting the group through the air lock, Eads gave a tour of the caisson and relayed a few messages to demonstrate the telegraph’s connection to offices on the pier top and the St. Louis levee. Eads and his guests enjoyed several bottles of champagne, toasted one another, and entertained themselves by attempting to whistle, which proved impossible in the dense air.
The atmosphere within the caissons played havoc with sound waves, lifting pitches upward into what the Missouri Republican described as “a decidedly nasal twang.” After a few minutes many visitors felt (in the words of one of them) “an exhilaration all through our system” and found that the abundant oxygen “produced upon us all a most pleasant, refreshing and invigorating effect.” Another curiosity was that candles were nearly impossible to extinguish. Eads once “blew a candle out thirteen times in the course of half a minute, the flame making twelve returns to the wick.”
Most visitors spent about half an hour touring the caissons, inspecting the riverbed, watching the workmen, and hearing about the excavation’s progress. Eads’s ingenious sand pumps proved singularly novel, and the inventor was plainly proud of them. Strangest of all, perhaps, was the chance to witness a “settling,” when the caisson and its mass of masonry suddenly shifted downward into the riverbed. The pier usually settled only an inch or two at a time, yet to a startled observer on or within it, the drop often seemed like a foot or more.
Although intrigued with the caisson, after twenty minutes or so most visitors started feeling anxious. To remain any longer, one St. Louisan wrote, was “to trust the truthfulness of figures and the deducions [ sic ] of science beyond the fullest consent of the nervous system.” Most visitors gladly re-entered the air lock, endured the screaming hiss once again, shivered as the temperature plummeted, and emerged in a few minutes to climb the stairs to daylight.
The workers, of course, had no such option. And magnificent as Eads’s engineering triumph was, there emerged one fundamental problem that his faith in scientific laws had neither anticipated nor resolved. The trouble started gradually, when the east caisson was just 15 feet deep in the riverbed, with 24 pounds of pressure filling the work chamber. A number of workmen suddenly began suffering sharp pains in their limbs and joints after leaving the caisson, aches much more intense than the normal workday soreness. At first the pains tended to abate after a few hours, and so long as the men recovered rapidly, most workers refused to worry, even joking at their unfortunate fellows. The seizures often left men bent forward with back pains, and the affliction was dubbed the Grecian Bend, after a style of women’s dress that put wearers in a similar stance. Later the name was shortened to “the bends.”
Eads had heard mention of such troubles while examining the French caissons, but he left Europe with the impression that the problems were nothing more than an inconvenience. Basing his opinion on the experience of diving-bell workers, he believed that the “question of the ability of human beings to work at the depth of one hundred feet below the surface of the water has been settled.” As the pier sank deeper and the pressure within the caisson increased, however, the afflictions got worse. Sufferers began relying on hot baths and patent liniments with names like Magic Oil and King of Pains. When these treatments proved ineffective, many workers started wearing “voltaic belts” made from zinc and silver plates around their arms, wrists, and waists and even beneath the soles of their feet. According to Eads, moisture from perspiration was supposed to establish “galvanic action in the armor,” which would somehow protect the men.
Despite these supposed remedies, the number of men falling ill increased, and their suffering grew more intense. Sore limbs and joints gave way to savage pains in the abdomen and back and even partial paralysis of arms and legs. In early February some men became completely paralyzed, remaining in agony for days on end. Eads cleared space on one of the pontoons for care of the stricken workers, but no treatment was very effective. On February 15, with the caisson 76 feet underwater and nearly 35 pounds of pressure inside, Eads began sending men to St. Louis City Hospital. Yet while a handful of victims writhed in agony, most of the workers remained fine, and no caisson tourists suffered. Crediting their health to superior stamina or simple good fortune, the men continued the arduous labor of digging through the riverbed.
Shortly after six on the morning of February 28, 1870, the cutting edge of the east pier caisson hit bedrock, 95 feet below the day’s waterline and 119 feet below the high-water mark. One of the bridge company’s barges fired a ten-gun salute; flags were unfurled; steamboats blew their whistles in celebration. With the east pier resting on rock and just 23 feet of sand remaining below the west pier, the Republican reported that the “event practically solves the most important problem associated with the building of the St. Louis and Illinois Bridge. … The rock has been reached without accident of any kind, and the balance of the work is comparatively easy.”
The newspaper’s sunny assessment was open to question, because the agony of the caisson workers had become a serious problem. Eads did not know what to make of the situation, the only problem attached to the bridge construction that stumped him. He realized, of course, that the difficulties had to do with the enormous compression of air in the caissons, and he regretted that as “the depth penetrated by the air-chamber was considerably greater than that hitherto reached in any similar work,” he gained no “benefit from the experience of others.” (Knowledge gained from diving bells was clearly no longer valid.) According to the engineers on duty at the piers, many of those taken ill were men of poor habits, underfed, overliquored, and thinly dressed. Workers most recently hired seemed most susceptible.
Some suspected that the shock of passing through the locks brought on the symptoms, but Eads dismissed this explanation, pointing out that the lock tenders, who continuously ran back and forth between the two atmospheres, had never once been afflicted. The pier engineers also noticed that the illness tended to attack men who remained in the caissons the longest, which, they reasoned, might explain why lock tenders never suffered, as they rarely spent more than a few minutes in the chambers. Eads placed greater stock in this explanation, and he reduced the length of shifts from four to three hours.
Still the suffering continued. While pressing the work forward, Eads remained compassionate, equipping the men with galvanic armor at company expense and spending an unspecified “large amount of money” to provide for the care of seriously afflicted men and their families. One disabled worker, after signing an agreement “forever discharging & releasing the Company from any & all claims,” received a thousand dollars to take a European health cure.
AROUND NOON ON FEBRU ary 28, just a few hours after the east pier hit rock, a St. Louis doctor and friend of Eads named Alphonse Jaminet visited the caisson. Jaminet had gone to the chamber several times before, conducting experiments to measure the influence of pressure on the boiling point of water. After nearly three hours working on the bedrock, he entered the air lock with Eads, and as usual when Eads depressurized, the exit valve was opened all the way. The passage from 45 psi took about three and a half minutes. As air rushed from the lock and the temperature dipped, Jaminet felt a sharp pain in his head. Afterward, as he climbed to the pier top, Jaminet’s pulse was racing, and in a few minutes he felt pains in his abdomen and became dizzy. He rode a ferry to the St. Louis shore, then struggled to walk the short distance to his buggy. Jaminet drove home, where he collapsed in agony.
Unable to speak clearly, Jaminet signaled his wife to position him on his back and prop his legs up slightly. After taking three teaspoons of rum, Jaminet held ice in his mouth to quench his thirst and began sipping spoonfuls of beef tea every five minutes. His pains, however, did not abate: “I was suffering from profuse cold perspiration, every effort to speak caused great suffering and fainting, my pulse was 106 per minute, both legs and my left arm were paralyzed, still I was suffering in both with excruciating pains which I can only compare to pains felt after a fracture of the left leg, which I experienced some years ago. During the pains in my limbs, which increased at intervals, my pulse was 115 per minute.”
Jaminet collapsed in his study at two-thirty in the afternoon and stayed there for the next three hours. “Any attempt to remove my clothing occasioned fainting … the least deviation of my body or any part of it increased the intensity of my sufferings.” He continued to take beef tea and ice, and by late afternoon the pain had eased enough for him to be moved to bed. Around six his perspiration began to subside, his pulse slowed somewhat, and he considered himself “out of immediate danger.” By ninethirty that evening he began to move his legs again, then slept intermittently through the night, “awakened from time to time by the suffering when trying to move.” At seven the next morning he could sit in bed. Later in the day he succeeded in shuffling across a floor.
Jaminet remained feeble for the next week before regaining his health. Many caisson workers were less fortunate. The worst cases began just after Jaminet’s seizure and continued through the next two months. Many men required care at the pier—usually a hot bath or vigorous massage—and by mid-March nearly twenty of the most severely afflicted had been sent to City Hospital. On the brisk morning of Saturday, March 19, the situation suddenly grew even more dire. James Riley emerged from the pier stairwell after a two-hour shift, told a friend that he felt fine, then abruptly gasped, toppled over, and died. Later in the day a second man died at the hospital. In the seven days following Riley’s death, the City Hospital admitted thirteen “bridge cases.” Most of these men recovered after several days of agony, though one remained ill for nine months and three died.
The first autopsy of a caisson worker took place on March 20. The subject was thirty-five-year-old James Moran, the second to die. Moran had spent just two hours in the air chamber, on March 14, and performed no labor there; he was visiting to determine “whether he could stand the pressure of the atmosphere therein, before engaging to work.” Shortly after leaving, he felt pains and fell into paralysis. He died in the hospital five days later. Moran’s autopsy, and four others that were performed on subsequent bridge fatalities, revealed many stretched and swollen blood vessels, overcharged with “dark and tarry blood,” and particular inflammation around the brain, spine, and vital organs. In some men the spinal cord and cerebral tissue were softened, “in many places to a pulpy consistency.” None of the postmortems, however, provided a very clear picture of exactly what had killed the workers.
Beyond the obvious conclusion that caisson pressure lay behind the suffering and deaths, the coroners remained unsure of what was happening. One doctor believed that rapid depressurization caused the problems, arguing that when the pressure was suddenly removed from the body, “all of the blood vessels, and more particularly the capillaries become distended, and in cases of death remain so.” A second physician, however, doubted that depressurization played any role, arguing that if a man’s hand was held in flame, “it would not be the reaction caused by suddenly taking it out that would affect or injure the person; it would be the first act of subjecting him to fire.” Rather, he asserted, the men suffered from too-rapid pressurization, which “forces blood from the smaller vessels to the heart, which necessarily acts more rapidly, thereby exhausting the energy and prostrating the subject.”
The first doctor to present a more complex analysis was a medical professor named Louis Bauer. Bauer began with the physicist’s observation that a liquid in pressurized air absorbs more gas than it does in a normal atmosphere. Assuming that human blood behaves in the same manner, Bauer reasoned that men within the caissons absorbed unnaturally high amounts of oxygen into their bloodstreams. This surplus of oxygen, he argued, fueled an increase in the workers’ metabolism, which resulted in greater production of gaseous waste products from respiration. The blood also carried this waste, he continued, and so long as the men remained under pressurized air, the respiratory system released it from the blood naturally. The danger, Bauer thought, occurred as workers exited the caisson, when the sudden loss of pressure disrupted the removal of “effete” gases from the bloodstream and allowed metabolic waste to be caught within the body, becoming a “most effective morbific agent, a sort of poison to the system.”
By far the most extensive study of the sickness was undertaken by Dr. Jaminet, whom the bridge company put in charge of the pier hospital. He courageously returned to the caissons time and again, conducting a careful investigation and ultimately producing an exceedingly detailed monograph. His inquiry was energetic, recording temperature, barometric pressure, pulse rates, time spent passing through air locks, and even the specific gravity of urine produced at different pressures.
Jaminet largely agreed with the physicians from City Hospital, which is to say that beyond the obvious culprit of air pressure, he did not know what was going on. His clearest articulation borrowed from Bauer, expressing the disease as a problem of accelerated “exhaustion of the system” fueled by the abundance of oxygen in the caisson. Jaminet also saw a connection between depressurization and the onset of the affliction, noting that workers fell ill only “after returning into the normal atmosphere. None, and we repeat it from official authority, were taken sick in the air chambers.” Upon these observations, Jaminet theorized that caisson labor left men in a state of hyperexhaustion and that rapid fluctuations of pressure and temperature within the locks exacerbated this fatigue, leading in acute cases to the sort of internal inflammation of organs and blood vessels seen in the autopsies. The best protection, he argued, was to work fewer hours in the caissons, pass through the locks more slowly, and rest more fully between shifts.
By the time Jaminet began work, on March 31, several dozen laborers had suffered serious attacks and eleven had died. The men were in the process of cementing the east-pier caisson, at a pressure of approximately 45 to 48 psi, working three shifts of two hours apiece per day, with two hours off in between. Jaminet began by changing the work schedule. Hoping to compensate for the accelerated fatigue that he believed occurred in the caisson, he increased the time between shifts from two to three hours. Additionally, he instructed the workers to “rest and keep quiet” for at least an hour following each shift, rather than “running around and going to shore to take a drink or more.” Eager to facilitate such repose, he improved the pier facilities, installing berths where the men could lie down and relax.
Finally, Jaminet instructed the lock tenders to slow passage into and out of the caisson. When workers “had with them a new or green hand,” he complained, they “enjoyed the fun of letting the compressed air to come in very fast,” scaring the wits out of the new employee by adding nearly 50 pounds of pressure in five to six minutes. Anxious to leave at the end of a shift, the men depressurized even more quickly, rushing through the lock in three or four minutes. Jaminet directed the lock tenders to pressurize no faster than 3 pounds per minute and to depressurize at 6 pounds per minute.
BELIEVING THAT VICTIMS OF hyperexhaustion needed immediate and complete rest, Jaminet expanded the pier hospital to treat as many as fourteen patients and directed “that under no circumstances should any one be removed from the pier to any other place.” Workers received substantially the same therapy that Jaminet had taken himself when afflicted in February. The patient was laid in bed on his back or right side, with his head low and legs elevated, a positioning that Jaminet hoped would “send more stimulus to the brain” and, by shifting from the back to the right side, alternately relieve the spine and heart. The patient was given liquor to relieve abdominal pains, offered ice to quench thirst, and then every five to ten minutes for the next several hours spoonfed hearty beef tea, which Jaminet believed would restore depleted energy. In most cases the men recovered significantly within eight to ten hours and were sent home. The majority of patients returned to the caissons within a few days.
IN SPITE OF HIS MANY EFFORTS , though, workers continued to suffer, and Jaminet grew quite frustrated, complaining to Eads that he could not “control the men and persuade them to keep quiet and rest.” Twelve serious cases occurred during the first nine days of April, including three attacks of partial paralysis that lingered into the summer. Jaminet reduced the work schedule several more times, ultimately canceling night work and requiring just two shifts of forty-five minutes from the laborers, but he still believed that the men were ignoring his simple regulations. Instead of “going home to keep quiet and rest,” he wrote, “the most of them were wasting their time of repose in bar-rooms or other places unfit for any man employed in such exhausting work.”
In mid-May, when he learned that the lock tenders were continuing to depressurize rapidly, Jaminet installed smaller air valves, making it impossible for passage to proceed faster than he advised. At about the same time, he began daily examinations of all caisson workers, assigning those who looked weak or tired to different tasks. Though Jaminet credited his examinations for the lack of fatalities in the last two weeks of cementing, there were still ten seizures during this time. Cementing of the river caissons was completed in late May, by which time Jaminet had recorded forty-nine cases. Two men had died under Jaminet’s care, one at each pier.
A twenty-one-gun salute and a chorus of steamboat whistles announced the end of the caisson cementing. With the two river piers now solid from bedrock to waterline, Eads had just one caisson left to sink—the east abutment, which would support the bridge approach along the Illinois shoreline. The bedrock there was deeper than under any other part of the bridge, nearly 130 feet below high water. Yet, the Republican noted, “with the experience gained in the other two piers, no difficulty is anticipated.” Later in the same piece the writer hedged a bit: “With the completion of this work, the dangers of compressed air to workmen will be at an end forever in connection with the bridge.”
As construction of the east abutment caisson got under way in the late summer of 1870, Jaminet gave Eads an extensive set of medical recommendations and design improvements. Larger air locks were built to cushion the shock of pressure change, and an elevator was installed to eliminate the long, tiring stairwell climb. Within the work chamber new lamps were used, designed to funnel smoke out of the caisson. When sinking of the abutment began, Jaminet continued his systematic examinations, inspecting the work force three times daily. Before new men were hired, he tested the fitness of each one, ultimately approving sixtyfour men and rejecting sixty-seven for reasons ranging from epilepsy to chills to “general debility.” Two new buildings were outfitted with berths, and each man was kept on the premises between shifts and required to eat a hearty meal, washed down with pints of beef tea. Finally, as at the piers, Jaminet directed that the work schedule taper as air pressure increased. By the time the caisson hit bedrock in late March 1871, 127 feet below the Mississippi’s high water, the men were working just two shifts of forty-five minutes, with six hours of rest in between.
Still, twenty-eight seizures and one death occurred before the filling of the east-abutment caisson was completed in late April. As before, Jaminet attributed many of these afflictions, including the death, to disregard of his regulations. He also pointed to a few days when the elevator was broken, leaving the men to climb 170 steps to the top of the abutment—further proof, he claimed, of “the theory of exhaustion.” When the last caisson was closed, Jaminet wrote that “by the strictest compliance with certain rules … compressed air can be used with comparative safety, even at the pressure of fifty-five (55) pounds to the square inch.” The evidence—14 deaths and 119 severe cases—might have argued otherwise.
Caisson disease is well understood by modern medicine. Although Jaminet never discovered the cause, it turned out that Louis Bauer, the St. Louis medical professor, had come quite close. Just as Bauer suspected, the problem is rooted in the way changes in air pressure affect the body’s ability to process gases. As pressure rises, more gas is absorbed. This condition is not dangerous in itself, for as Bauer realized, as long as pressure remains fairly constant, gases are picked up and discharged naturally through the lungs. Nor is there much danger if one stays under pressure only briefly, for gases require time to dissolve into the body fluids.
The problem occurs when one remains under high pressure for an extended time and then exits the pressurized atmosphere suddenly, as was the case when caisson workers hurried through the lock at the end of a shift. As pressure decreases, the body can no longer hold the volume of gas that has been absorbed. If depressurization proceeds gradually, the body will release the excess gases naturally. If pressure is let off quickly, however, dissolved gas cannot escape, and as the blood and tissues become physically incapable of holding it in solution, the gas emerges and forms bubbles.
The great danger comes from nitrogen. Most common gases, like oxygen, enter and exit solution fast enough to escape as pressure is removed, but nitrogen does so very slowly and thus is likely to stay in body tissues after a loss of pressure. As the gas precipitates, pockets of it can obstruct capillaries, blocking the flow of blood and causing enormous pain. If this happens in the spinal or cerebral areas, paralysis, long-term disability, and even death can occur. Had Bauer refined his theory through further investigation, he might well have solved the problem. Jaminet took a step in the right direction with the installation of smaller valves in the air locks to slow depressurization, but this measure proved far too slight. Jaminet’s regulations slowed depressurization to 6 pounds per minute. A healthy rate would have been close to three-quarters of a pound per minute.
MOST IRON ic and sad, though, is the fact that years before Eads began sinking his caissons, two French researchers named Pol and Watelle had largely resolved the difficulties of working in compressed air. The two studied the effects of pressure in French coal mines, where as early as 1841 compression was used to force water away from the work site. They explained their research in an article published in 1854, in which they detailed the first two known fatalities caused by rapid loss of air pressure. “Experience has shown,” they wrote, “that the bad effects of decompression are directly proportional to its speed.” Had Eads or Jaminet known any of this, perhaps they could have halted the daily agony and spared fourteen lives.
Yet perhaps not. In New York’s East River on March 19, 1870—the very day that the first worker died at St. Louis—Washington Roebling launched the first of two caissons that would support his masterpiece, the Brooklyn Bridge. Roebling had met with Eads, and he incorporated some of the St. Louis designs into his own caissons, which were more than double the size of those in the Mississippi. Like Eads, Roebling hired a doctor to oversee the work site. Not only was Roebling’s doctor familiar with Jaminet’s investigation; more important, he had read Pol and Watelle’s study and knew the work of another French doctor, Antoine Foley, who had arrived at the same conclusions in 1863. Even so, as the larger of the East River caissons approached its ultimate depth of seventyeight feet six inches below high water, workers endured the same vicious pains, three men died, and Roebling himself suffered a savage attack that left him an invalid for the rest of his long life.
The Eads Bridge, as it began to be called even before its completion, had its official opening on July 4, 1874. The years since have demonstrated the worth of Eads’s confidence in his own talents and the laws of nature. His bridge remains one of the great engineering successes of the nineteenth century, and its pier foundations remain among the very deepest in the world. The caisson method has become a mainstay of civil engineering.
As a business venture, however, the bridge was a failure. It had been envisioned as a connection between St. Louis and the Eastern rail markets, designed to lure the economic energy of Manifest Destiny through Missouri. Eads himself, as a major shareholder in several railroads, must have been particularly hopeful. Chicago had been investing in rail lines since the 1840s, though, and by the time St. Louis completed its bridge, most Midwestern railroads either were owned or controlled in Chicago or already ran through that city and saw no immediate need to route traffic through St. Louis. Without the revenues they had expected, the members of the bridge company found themselves holding a beautiful bridge and millions of dollars worth of debt. They declared bankruptcy in April 1875, not even a year after the grand opening.
