14
As it is now demonstrated that the method of compressed air is applicable to a great range of engineering operations, and offers many peculiar advantages, it is extremely desirable that the principal objection to its employment, viz., the discomfort and danger to the workmen, should be reduced to a minimum. To this end I offer the following suggestions…
—ANDREW H. SMITH, M.D.,
The Effects of High Atmospheric Pressure, Including the Caisson Disease
SMITH said the caisson disease could be explained on mechanical principles. He said it was caused by the effect of abnormally high atmospheric pressure on the circulatory system. Under pressure, the blood was not distributed according to the normal physiological demands of the body, “but in obedience to overpowering physical force.” As he saw it the envelope of heavy air in the caisson pressed against the surface of the body forcing the blood into the center of the body. The blood “retreats,” he wrote, “from the surface to the center, and accumulates there until an equilibrium of pressure is produced.”
Smith held, however, that a man’s circulation could adjust somewhat to such unnatural conditions if the conditions were experienced by degrees. And the longer a man stayed down in the heavy air, and the heavier the air, the more the circulatory system would be affected. But when the pressure was removed suddenly—if a man were to waste no time getting through the air lock—then the blood vessels would fail to assume their natural condition in an instant, proper circulation would not be restored quickly enough, and “disturbance of function will result.”
Smith was quite right that rapid decompression was the secret to the mystery, but his explanation of why was wrong. His call for slower decompression was a commendable step in the right direction certainly, and seemed radically cautious at the time. (In St. Louis, for example, Dr. Jaminet wanted his men to spend an extra minute in the lock for every six new pounds of pressure, indicating that perhaps Smith’s convictions on the matter were twice as strong.) But even so, as a preventive measure, Smith’s new locking-out procedure, even when it was followed, was so inadequate as to be of little real consequence.
The mystifying disease was, in fact, caused by the effect of too rapid decompression on circulation, but for reasons other than Smith had arrived at. The leg pains, the paralysis, the swollen joints, the agonizing stomach cramps, were caused by the liberation of nitrogen bubbles from solution in the blood stream and in the tissues of the body upon the sharp reduction of atmospheric pressure.
Under pressure the normal nitrogen gas in the blood dissolves to a high degree, then returns to a gaseous state—in the form of bubbles—when and if the pressure is suddenly relieved. Set free in the body fluids such bubbles can cause great damage. If liberated in the spinal cord, for example, they can cause total paralysis. But if pressure is relieved gradually, the gas comes out of solution slowly and is removed by the lungs.
The savage pains of the bends are caused by a stoppage of the oxygen supply in the blood stream. The nitrogen bubbles released by too rapid decompression create blocks in the blood stream—the same as mechanical blocks—that keep the oxygen in the red blood cells from reaching the tissue. The red cells fail to get past the nitrogen bubble, the tissue is denied the oxygen it must have, and the result is dreadful pain. This denial of oxygen-bearing blood—called ischemia—is much the same as what happens in a heart attack. So an attack of the bends might be likened to a heart attack in different parts of the body, most often the limbs and joints.
The level of pressure in the caisson and the time spent by an individual in the caisson do have a direct bearing on the problem and so Smith was right to keep the work shifts as short as possible, a policy that is still adhered to in caisson and tunnel work when pressures are extreme. Smith’s nine rules were also sound policy, in that they contributed to the over-all fitness and health of the men and fit, healthy men are less likely to be victims of the bends than those who are not. Fat men are also more prone to attacks, as Smith surmised, since the nitrogen bubbles tend to collect and dissolve in fat tissue. And from all that is now known about the bends—from subsequent experience in construction work, from underwater research and the space program—it appears that some people are indeed more susceptible to the disease than others, just as Smith declared.
Smith was, in fact, a keen and intelligent observer and deserves great credit for his work. His thesis of slower decompression was the key to the puzzle. The only problem was he did not carry it anywhere near far enough.
A man’s health did depend mainly on how sudden and great a change he was subjected to on coming out of the caisson back to normal pressure. If there was to be damage done it happened then. Time in the caisson, the amount of pressure the men were working under, their individual physical make-up and condition, even the temperature both in and outside the caisson, were all important contributing factors. But it was the speed of the exit that really mattered. And by modern standards the men in the New York caisson were making their exits disastrously fast—even when doing as Smith wanted and taking a few extra minutes in the lock. Today the accepted safe rate of decompression is no less than twenty minutes for each atmosphere, or more than a minute for every pound of pressure. So by that standard, at a depth of sixty-five feet in April of 1872, every man coming up from the New York caisson should have spent at least twenty minutes in the lock, instead of two or three as was the average, or five or six as Smith urged.
That bubbles of nitrogen were the true cause of the dreaded disorder had already been discovered in France by a professor named Paul Bert, and at about the same time Smith was conducting his research. But the discovery would not be published until August of that year, and although Smith would read what Bert had concluded before formally presenting his own conclusions, he would decide that Bert was mistaken.
Smith was quite right about one other very crucial matter: how to relieve the agony of the disease. Just when the answer dawned on him is not clear, but it appears quite noticeably twice in his case notes.
The first time was in February, in the case of the foreman Joseph Brown, already quoted. “Pain continued until he went down again for the afternoon watch, when it ceased immediately.” Then in April, Smith described the case of another foreman named Card, who was hit by an attack of extreme trembling, followed by paralysis in the legs and bladder. Smith writes that the man remained in this state for two full days, but then adds, “After the paralysis had passed off in a measure, he went down again into the caisson and remained for a short time with decided benefit.”
The quickest, surest way to relieve the pain was to send the patient right back into compression and when it came time for Smith to present his final report the next year he would write this:
It frequently happened under my observation that pains not sufficiently severe to deter men from returning to work were promptly dissipated on entering the caisson, to return again on coming into the open air. Indeed, I do not remember a single exception to the rule, that any pain which may have been felt before, disappeared almost immediately on going down.
Smith was aware, too, that Pol had prescribed returning the patient at once to the compressed air and that Dr. Antoine Foley, also of France, had said the same thing in a paper published in 1863. Later that same spring of 1872, in his own annual report, Roebling would write that most men got over their troubles either by suffering for a time or “by applying the heroic mode of returning into the caisson at once as soon as pains manifested themselves.”
But the puzzling thing is that Smith never seems to have actually prescribed this “heroic mode.” Not once, according to the records, was a man suffering from a violent attack of the bends taken back down into the caisson. It was only the man who felt fit enough to go down on his own, to work, who ever benefited from this simplest and most effective of all remedies. Smith’s explanation was that the means of access to the caisson were such that to take any but a comparatively healthy patient down inside would have been too difficult—“even if he could be comfortably cared for while there, or if his presence would not interfere with the work.” The remedy was just too much bother, he seems to be saying. It would have deterred progress the same as would more time taken in locking out.
But equally important, it seems, was the fixed idea most of the men had that the pressure itself was the cause of the trouble. They could not get rid of that idea. The thought of going back for more pressure when they were in their agony—of getting back on the horse, so to speak—was more than any of them were up to and particularly if neither the doctor nor the engineers in charge ever insisted on it. The less risky course seemed simply to hold on and suffer it out.
At a depth of sixty-eight feet the caisson’s steady plunge into the earth slowed abruptly. The men were into quicksand now and the going became extremely tedious. The big clamshell dredge buckets dropping down the water shafts were almost useless against the fine sand that, in combination with small stones and boulders, had compacted into a substance about as hard as rock. The teeth of the buckets made hardly any headway at all. The point of a crowbar could be hammered into the material, but just barely. And though the sand pipes still “answered admirably,” as Roebling put it, even they were constantly clogging with coarse gravel and stones. The speed of descent was now perhaps a foot a week.
At a depth of seventy feet Roebling ordered that daily soundings be taken for bedrock. So a couple of men with sledge hammers and a ten-foot iron rod began probing the work surface and among the others there was talk of the caisson going twenty or thirty feet more before Roebling would call a halt. Then at a depth of seventy-one feet the first death occurred.
On the morning of April 22, a heavy-set German, a common laborer, went down through one of the air locks and into the caisson for the first time. Two days before, when he applied for work, the man had given the name of John Myers. Dr. Smith had judged him to be about forty and in good health. The pressure by this time was thirty-four pounds, and the workday, shortened once again, was five hours.
According to Smith’s subsequent account of the case, Myers worked the morning shift, just two and a half hours, without any discomfort, and hung about the yard for nearly an hour after coming up, apparently heeding the doctor’s rules about rest. But then he had complained of not feeling well and started for his boardinghouse, which was quite close by. “As he passed through the lower story of the house,” Smith wrote, “on his way to his room, which was on the second floor, he complained of pain in the abdomen. While ascending the stairs, and when nearly at the top, he sank down insensible, and was dead before he could be laid upon his bed.” An autopsy at the city morgue showed that brain, heart, and kidneys were perfectly normal. The lungs, however, as Smith reported, were “congested to a very remarkable degree.”
On April 30, just eight days later, with the pressure still at thirty-four pounds, Patrick McKay, of Ireland, age fifty, was listed as the second fatality attributable to the caisson disease. McKay had been working in the caisson for four months with no ill effect. On the afternoon of the 30th he had stayed down a half hour longer than usual, and on his way out through the lock, the others in the lock saw him suddenly slump to the floor, his back against the iron wall, quite insensible. He was at once carried into the open air and taken to Park Hospital, where Smith looked in on him some time later that evening. “He was there in an unconscious condition,” Smith wrote in his notebook; “face pale and dusky; lips blue; pulse irregular and feeble. Under the administration of stimulants, he recovered some degree of consciousness, and begged incessantly for water.” But only a little later the man went into convulsions and died. This time, however, the autopsy indicated Bright’s disease in the kidneys and Smith would conclude that “the effect of the compressed air was merely to hasten an event which, at best, could not have been very long delayed.”
Be that as it may, the word was out—not just among the work crew, but everywhere in the neighborhood of the bridge—that men were dropping dead of caisson sickness. A third man who had died some time earlier of spinal meningitis was also said to have been a victim, “if the truth were known.” The stories became greatly exaggerated and spread like wildfire through the crowded tenements near the site of the New York tower.
One of the children to grow up on South Street in the 1870’s was Al Smith, who would one day be almost as much a symbol of New York as the bridge itself. In later years he would describe his mother talking in tones of awe about the many workers who had died while struggling to sink the great caissons. “Perhaps if they had known,” she had said, “they would never have built it.”
On May 2 a man named Heffner began vomiting and despite everything done for him he was still vomiting twenty-four hours later. On May 8 the entire force of caisson men went out on strike. They stood about in the street nearby, talking to newspaper reporters and anyone else who would listen. Conditions below had become so dangerous, so terrifying, they said, that they wanted three dollars for a four-hour day. By noon or thereabouts the Bridge Company had agreed to $2.75, but the men turned that down angrily and a man who tried to break through their lines was badly beaten. Negotiations dragged on for another three days. But then William Kingsley announced that if the men did not all go back to work immediately he would fire every last one of them and with that the strike ended.
There were more attacks of the bends during the next week and the caisson kept descending little by little. From the soundings Roebling had ordered, a picture of the underlying bedrock had begun to emerge.
“The surface was evidently very irregular,” he wrote, “composed of alternate projections and depressions, the extreme difference in elevations encountered being 16 feet, and occurring chiefly along the water edge.” Throughout the central section, however, and covering at least two-thirds of the entire area, the irregularities were much less, amounting to maybe no more than three or four feet. As near as he could tell, the caisson was about to settle on a broken ridge of rock running diagonally from one corner of the caisson to the other and having a dip of perhaps five feet in a hundred toward the land, but falling off rapidly toward the east.
Roebling now faced what would be the most difficult decision of his career. He himself was very near to a physical collapse. He had been spending as much time in the caisson as anyone, but going up and down through the locks, to check on this or that below, many times more often than the average laborer. He was on the job constantly, working twelve to fourteen hours a day, six days a week, frequently making three and four trips a day on the ferry, going back and forth from the Brooklyn offices. Most of his time was spent on the site itself. But it was the only way he could have worked. He was not an office engineer and had little regard for those who were.
At this point he could either keep the caisson descending until he had level rock on which to leave it or he could stop about where he was, before reaching rock. To continue deeper would mean enormous expense and time lost blasting the irregular rock ridge down to a comparatively even surface. It might also mean more lives lost. Already Smith had recorded more cases of the bends than Jaminet had in St. Louis. And whereas Eads had not suffered a single fatality until his first caisson was down ninety-four feet and the pressure was at forty-four pounds, Roebling, for some unknown reason, had already lost two men. So at this rate the New York caisson might take even more lives than the thirteen the St. Louis foundations had cost by the time they were in place.
Emily Roebling would remark later that her husband estimated it would take another year to go to bedrock and that it would cost another half a million dollars and possibly a hundred lives.
To leave the tower standing on anything other than bedrock, however, would seem to put the stability of the entire bridge in jeopardy. Yet Roebling, to the surprise of many, was now not so sure about that. The sand and gravel covering the rock was so compact, so very hard, he said, that it might provide as solid a footing as rock itself. Earlier, when they were down sixty feet or so, the men had uncovered the bones of a domestic sheep, and just below that fragments of brick and pottery, indicating that the strata at that level had changed within the time man had been around. But in the last ten feet and more, no such evidence had been unearthed; the strata showed no signs of having been disturbed since the time of deposit several millions of years in the geologic past and so in all likelihood it would remain perfectly stable. As Roebling noted, it was now nearly impossible to drive in an iron rod without battering it to pieces. The material, he would write in his forthcoming report, was “good enough to found upon, or at any rate nearly as good as any concrete that could be put in place of it.”
If he was right about this, then the enormous stone tower could rest there as well as anywhere and his problems would be solved. But if he was wrong, then there was the chance that the tower might begin to lean or slip and the bridge would be a disastrous failure. Possibly, others noted, the tower might even slide into the river.
“The period of time at the end of the sinking of the New York caisson was,” his wife would say, “one of intense anxiety for Colonel Roebling.”
But the decision could wait a little.
At a depth of seventy-five feet the first spur of bedrock, the ordinary gneiss of Manhattan Island, was encountered under the shoe on the river side. “No part of its surface shows the rounding action of water or ice,” Roebling reported. “On the contrary, the outcrop is in the form of sharp thin ridges, with steep vertical sides occurring in parallel ranges.”
On May 17 one man became paralyzed in the legs and arms; another complained of savage pains in his legs; a third, an Englishman named Reardon, began retching violently after coming up from the afternoon shift. In minutes he was seized by excruciating leg cramps and pitched forward, unable to walk or stand. The vomiting continued all night and Dr. Smith had him taken to the Center Street Hospital, where he grew steadily worse. The following morning he died. Smith wrote in his notebook that Reardon had been “corpulent” and that the autopsy showed his spinal cord to be “intensely congested.”
That same day, May 18, 1872, with the caisson at a depth of seventy-eight feet six inches, Roebling ordered that the digging stop. He had decided not to go to bedrock, staking his reputation and career on the decision. The New York tower would rest on sand.
The second and last great caisson was therefore in position, and as Collingwood noted, the differences of level at the extreme corners, as measured on the masonry above, was only three-fourths of an inch. It had been a spectacular feat of engineering.
The work of filling the air chamber began at once and Roebling finished his report to the directors. If anyone was upset about the incidence of caisson sickness, Roebling said only that the trouble had not been so serious as he had anticipated. He made no mention of the number of cases there had been and claimed that just two deaths could be charged directly to the effects of pressure. As for the unsung individual suffering there had been, he said only this: “The labor below is always attended with a certain amount of risk to life and health, and those who face it daily are therefore deserving of more than ordinary credit.”
At the end of May, Dr. Smith resigned his position and went back to the Eye and Ear Hospital, satisfied his work was complete, his services no longer needed now that the caisson was at rest. But work inside the caisson continued right along, the concrete for filling it in being mixed above, then let down through the supply shafts. No brick piers were built this time; the caisson was quite strong enough on its own. (With 53,000 tons on its back, it showed not the slightest sign of deflection in the roof.) But about a third of the space was filled with stones, earth, and sand left inside during the sinking. With the concrete going in at the rate of one hundred cubic yards a day, Roebling figured to have the entire job done by early July. The saying was that the concrete would keep pouring into the caisson until there was room enough left for one last Irishman, who would make his final exit by one of the water shafts.
But some time before that happened, Roebling suffered another attack of the bends. There is nothing in the official record to indicate just when it happened, only that it was late spring, while the concrete work was going on. Apparently he collapsed again, as he had the night of the Brooklyn caisson fire, and he was immediately taken back to Brooklyn on the ferry.
Who was on hand to help him is not known. There would be nothing said of the incident in the papers, suggesting that perhaps he and the others wanted no more adverse publicity than they already had or that they thought the seizure would soon pass. He himself made only the briefest mention of what happened in a report published later that fall. The attack, he said, resulted from a stay of several hours in the caisson, suggesting that he still believed the time spent below was the determining factor and had never accepted Smith’s theory on speed of decompression. “Relief from the excruciating pain,” Roebling wrote, “was afforded in his [the writer’s] case by a hypodermic injection of morphine in the arm, where the pain was most intense, and a further stupefaction by morphine, taken for twenty-four hours internally until the pains abated.” According to Emily Roebling, however, in an account written a few years later, his condition was so serious the night of the attack that he was expected to die before morning.
There is no telling whether Smith was called back, whether the idea of returning to pressure (“the heroic mode”) was even considered, or if so, why it was rejected in favor of drugging the patient into a stupor.
For several days more Roebling lay near death in the same Hicks Street house where his father had died. His assistants came and went. Somebody was with him at all times. Little hope was held out for him. In some of the things written about him a generation later, it would be said that Roebling remained painfully paralyzed, a total invalid from this point on. But the record shows this was not the case. In another few days, much to everyone’s amazement, he went back to work.
Once when he was seventeen, his father had been faced with a cholera epidemic at Niagara Falls. More than sixty people had died in the first week and the doctors seemed incapable of doing anything to help. “The great secret,” his father had written to Charles Swan, was to “keep off fear.” His father, too, would have succumbed with the rest, according to one man who was there, had it not been for his uncommon powers of concentration. “He determined not to have it,” the man wrote. John Roebling had spent one whole night walking up and down his room, fighting to rid his mind of the very thought of cholera. The incident made an enormous impression on the gentleman who witnessed it and on everyone back in Trenton when the story was told there. Now it seems Washington Roebling too had “determined not to have it.” Other men might resign themselves to their fate, he could not.
Through the first weeks of summer the attacks kept recurring, however, and he suffered intensely. He made no public mention of this, nor did anybody else. It is only from comments made in private correspondence years afterward that anything is known of his extreme physical suffering. To judge by the Bridge Company’s record books and occasional items in the papers, he was carrying on as though nothing were the matter. It was during this time, for instance, that his report exonerating the management of Bridge Company purchases was read before the board, and knowing this, one cannot but wonder if his physical and emotional torment, the anxiety Emily described, did not have something to do with the discrepancies between that report and some of the things he would say privately much later on.
On July 12 the filling in of the New York caisson was completed and apparently under the personal supervision of the Chief Engineer. The whole task of sinking the caisson had taken 221 days.
He took two weeks off and went with Emily to Saratoga. He was somewhat improved when they returned but that lasted only briefly. By September he was staying home two and three days a week. Still his condition remained a private matter. To judge by the official records and items in the papers the Chief Engineer was very much on the job.
On September 3 bills amounting to $50,000 were ordered paid, on being certified by the Chief Engineer. On September 17 the Chief Engineer was directed to solicit bids for the anchor bars for the New York anchorage and the Chief Engineer and the General Superintendent were authorized to award the contract to the lowest bidder. On October 8 the Executive Committee authorized the president of the Bridge Company to execute a contract with the Bodwell Granite Company of Maine, according to specifications prepared by the Chief Engineer. An agreement made by the Chief Engineer with Louis Osborne of East Boston, for building an expensive double hoisting engine, was also approved, and a number of substantial bills were ordered paid, after being certified by the Chief Engineer.
In late November it was Roebling who ordered that work on the Brooklyn tower be suspended for the winter. The tower by then had reached a height of about 145 feet, or well beyond the level where the bridge deck would be. It was no longer a solid flat-topped shaft. Now the beginning of the great archways could be seen thrusting upward like three immense teeth separated by the two gaping spaces left for the roadways.
It was in December, the same month the Committee of Investigation presented its findings, that work on the New York tower was halted, on account of the weather, at a height of nearly sixty feet. And it was in December that Washington Roebling found he was unable to go down to the bridge anymore. His condition was very serious now, extremely puzzling, and a closely guarded secret among the relative handful of men who were running things inside the bridge offices.
The sudden, violent cramps, the awful dizziness and vomiting had ended after the first horrible days in early summer, just as had been the experience of every other victim from the caisson, indeed as had been his own experience the time before. But the pains and the numbness had continued, coming and going, in his arms and legs primarily. He tired rapidly. He was sick at his stomach much of the time. He became extremely irritable and distraught over the slightest problems or inconveniences and slipped into moods of profound gloom that lasted for days. By December he was a very sick man. Still, he refused to give up. “He was never known to give in or own himself beaten,” the men at the mill had said of his father.
Emily Roebling went to see Henry Murphy, to talk privately about the situation. Her husband was determined to continue as Chief Engineer, she said. Murphy told her that that would be agreeable with him, just so long as nothing went wrong at the bridge. She expected his troubles would last but a short time.
Total rest was the only cure prescribed for him through that winter, and Emily was apparently about the only person he wanted anywhere near him for any length of time. The doctors kept telling her that he had little chance of recovery, that she should be prepared for the worst, while he himself had become obsessed with the idea that he would not live to see the bridge finished. And knowing better than anyone how incomplete the plans and instructions for the remaining work still were, he spent that entire winter writing down, in his minute, meticulous hand, all that had to be done, filling page after page with the most exacting, painstaking directions for making the cables, for assembling the complicated components of the superstructure, and illustrating these with detailed freehand drawings and diagrams.
There was no work going on at the bridge all this time, other than paper work at the Fulton Street offices. Snow piled up in the yards. The two towers stood idle on either side of the ice-choked river. But Roebling in his bedroom on Hicks Street labored on, fighting with everything he had. In his condition writing for even half an hour was a terrible strain. He became extremely nervous and found he could no longer carry on an extended conversation with his assistants, who had been reporting regularly for instructions. His eyes began to fail. He thought he was going blind.
By early spring, when the weather was such that the men could return to the towers, it was common knowledge among the bridge workers that the Chief Engineer would not be resuming his command for some time, if ever. It had been decided that C. C. Martin would be authorized to certify bills and the masonry work would proceed as before. In April Roebling formally requested a leave of absence. His doctors had told him his only chance to live was to get away from his work. He and Emily had decided to go to Europe, to the health baths at Wiesbaden. The trip would be a frightful ordeal for him, but in this the darkest time he had ever known, he would turn for relief to Germany and the water cure. His feelings at the time can only be guessed at. But possibly in quiet desperation, everything else having failed, he had concluded that if the ways of his father had put him in this corner, then perhaps they might get him out as well.
Later that same spring of 1873, Dr. Andrew H. Smith presented the formal report on his experience as Surgeon to the New York Bridge Company, in which he included certain suggestions for future projects of a similar nature. The most important thing to do, he said, was to have some sort of facilities by which compressed air could be readily accessible above ground.
My plan would be as follows: Let there be constructed of iron of sufficient thickness, a tube 9 feet long and 3½ feet in diameter, having one end permanently closed, and the other provided with a door opening inward, and closing airtight. This tube to be placed horizontally, and provided with ways upon which a bed could be slid into it. Very strong plates of glass set in the door and in the opposite end would admit the light of candles or gas jets placed immediately outside. This apparatus should be connected by means of a suitable tube with the pipe which conveys the air from the condensers to the caisson. An escape cock properly regulated would allow the constant escape of sufficient air to preserve the necessary purity of the atmosphere within.
The bed containing the patient having been slid into the chamber, the door is to be closed, and the pressure admitted gradually until it nearly or quite equals that in the caisson. This should be continued until the patient indicates by signal, previously concerted, that the pain is relieved. The pressure should then be reduced by degrees, carefully adjusted to the effect produced, until at last the normal standard is reached. By occupying several hours, if necessary, in the reduction of pressure, it is probable that a return of the pain could be avoided.
The concept of the apparatus described by Smith in this proposal is precisely the same as the so-called “hospital lock” used for modern bridge and tunnel construction, whenever men are working in compressed air. Had Smith installed such a device at the New York caisson, and had it been used in the way he describes, there would have been little or no suffering from the bends by anyone, there would have been no deaths, and the subsequent life of Washington Roebling and the story of the bridge would have been very different.