The Great Bridge (38 page)

But beneath this foul dock mud, which was only a few feet deep, they hit clean river sand and gravel, and things took an immediate turn for the better. The skim of water was expelled by compressed air, leaving a perfectly dry footing, and by now, too, the lights inside were fully operating and in combination with the white roof and walls they lit up the entire chamber as bright as day. From then on the great timber box descended into the earth extremely rapidly.

Above ground the scene was one of great energy and purpose. A reporter described it this way:

There were almost no boulders to contend with this time, indeed little else but sand. The average rate of descent would work out to about two feet a week, but at one stage, for several weeks, the caisson was sinking six to eleven inches a day. In the Brooklyn caisson, during the first discouraging month of excavation, the rate of descent had not averaged six inches a week. Now everything was working to perfection. The dredges had no trouble digging the pools below the water shafts and the sand pipes worked like a charm.

How the pipes were to be used exactly had been left undecided until it came time to give them a try. Either the sand could be forced out with water, using a new kind of sand pump devised by Eads, or it could be blown out by compressed air. The latter would be the simpler, less costly way, of course, if it worked. It would also greatly aid ventilation. An air chamber with an iron skin such as this one had inside would be practically airtight, but a certain quantity of new air had to be fed into the work area at all times to keep the atmosphere fresh enough to live in. In the Brooklyn caisson this had been no problem since air kept escaping under the shoe or into the timber roof. But compressed air lost that way did little work. Roebling’s thought, therefore, was that with all the compressors he had at hand, why not allow air to escape through the pipes and take sand out with it?

So the air system had been tried and after that there was no more talk of sand pumps. For everyone who remembered how it had been in Brooklyn this was the smoothest sailing imaginable. Morale could not have been better.

The sand pipes extended down through the roof and into the chamber to within a foot or so of the work surface. Sand, loose earth, and fine gravel were shoveled around the pipe in a cone-shaped pile two to three feet high. When the pipe was opened, the pile vanished up the pipe. It was as neat and uncomplicated as could be, and the deeper the caisson went—the greater the pressure in the chamber became—the better the system worked. When the caisson was down about sixty feet, for example, the air was blasting out of the sand pipes with such force that fourteen men could stand in a circle around one pipe and shovel sand under it with all their strength and the sand would disappear as fast as they could shovel. At least three sand pipes were kept going all the time and some sixty men did nothing but feed these pipes, which was about the most tiring work imaginable. Time and time again the pipes had to be shut off to give the men a rest.

Up on top the sand blasted out with such velocity that it became a serious problem. At first, when there were only vertical discharge pipes, the sand was shooting four hundred feet in the air. To deflect this great geyser off at right angles, so it would feed into big scows tied up beside the caisson, iron elbows were fixed to the tops of the pipes. But the furious blast of sand would cut right through these, sometimes in a matter of minutes. Iron an inch thick would not last a regular workday. When elbows fixed with thick caps or patches of a special chilled iron were tried, they lasted only two days. Toward the end of the work the elbows would be dispensed with altogether and heavy granite blocks would be placed on supports directly above the mouths of the pipes. The sand would strike the blocks, then fall back. But the sharp, abrasive force of the sand was such that in three or four days’ time it would cut a hole through the granite block.

Once, a man passing by in a rowboat, with one hand resting on the gunwale, had the end of a finger shot off by a pebble fired from a sand pipe. Another time a workman was drilled through the arm in the same way. And down inside the caisson Farrington at one point thoughtlessly placed his hand over the open end of a sand pipe and found he was unable to remove it. Only with several others pulling on his arm was he able to get his hand free and then found that his whole palm had been drawn up into the pipe like a stopper.

Boulders were encountered only on occasion and slowed things down but a little, except when one appeared directly below a water shaft. The shaft had to be capped then, the water removed, the boulder excavated out of the dry hole, the same as had been done so many times in Brooklyn. But relatively little time was lost that way. Paine’s “mechanical telegraph” between the men on top and those below worked amazingly well. “The downward movement of the caisson has been under perfect control,” Roebling wrote. Indeed, the work went smoother, faster than anyone could have hoped for. Everything functioned as it was supposed to in theory and as it seldom had in practice over in Brooklyn. Nothing very unexpected happened. The heavy, tiresome digging by the men inside and the noisy work of dredges and stone derricks up above continued day after day, six days a week, and on into winter. The caisson, itself as high as a four-story building, kept descending steadily, evenly, uneventfully, the lights inside burning twenty-four hours a day, and all the while an enormous load of limestone blocks piling up on its back just as steadily, evenly, and uneventfully.

As far as Roebling and his staff were concerned, there were only two problems to be considered—the effects of the compressed air on the men and the depth to which they might have to go before stopping. In Brooklyn every foot of ground gained had to be fought for and the physical discomfort of working under pressure had been but part of the problem. But here the mercury gauges on the big Burleigh compressors kept inching up just as steadily as the caisson was descending.

Every two feet gained meant a pound more of pressure. On December 18, when the caisson was grounded on the river bottom in thirty-seven feet of water, the pressure was at seventeen pounds. In Brooklyn the pressure had gotten up to only twenty-one pounds when that caisson was halted at a depth of forty-five feet. But here, where the water was so much deeper to begin with and the going so much easier, it took only about a month to reach forty-five feet. Even at that the bottom of the caisson was only eight feet into the river bed, which left twenty-three feet more, or the whole of the enormous timber roof, still surrounded by water. And bedrock was still a long way off. But at forty-five feet, just as at Brooklyn, some of the men began feeling a good deal of discomfort, and, in a few cases, severe pain.

The number of men employed at any one time in the caisson varied from fifty to 125 in the daytime and from fifteen to thirty during the night. At first the workday was divided into two shifts of four hours each, separated by an interval of two hours. But at forty-five feet Roebling ordered the workday for caisson men shortened slightly, to seven and a half hours, in two shifts. At fifty feet, with the pressure increased another two and a half pounds, the day was again cut by half an hour. The majority of men were having trouble by now. The climb up to the surface after each shift, for example, had become so terribly fatiguing that Roebling had one spiral stairway pulled out and a steam elevator installed, as Eads had also done in St. Louis.

It was not until late January, however, when the caisson reached a depth of fifty-one feet, that any serious effect among the men was observed. And it was at this point, when pressure in the chamber stood at twenty-four pounds, that Roebling decided there ought to be a doctor on hand.

His name was Andrew H. Smith. He was a New Yorker, a former Army doctor, a surgeon, and a throat specialist at the Manhattan Eye and Ear Hospital. He was a man about the age of Roebling. Nine years later he would achieve national prominence by performing the autopsy on President Garfield that revealed the much-debated location of the assassin’s fatal bullet. Smith’s pioneer work on the bends, however, would be of far greater importance. His title was Surgeon to the New York Bridge Company and, except for Dr. Jaminet, Eads’s medical adviser, and some other St. Louis doctors, he was the only man in the country with any medical background to try to figure out what was causing the mysterious malady brought on by compressed air.

Smith took his assignment very seriously and went right to work. His first step was to prepare a set of rules, just as Jaminet had done two years earlier in St. Louis. These he had posted conspicuously about the dock and inside the caisson. They read as follows:

Never enter the caisson with an empty stomach.


Use as far as possible a meat diet, and take warm coffee freely.


Always put on extra clothing on coming out, and avoid exposure to cold.


Exercise as little as may be during the first hour coming out, and lie down if possible.


Use intoxicating liquors sparingly; better not at all.


Take at least eight hours’ sleep every night.


See that the bowels are open every day.


Never enter the caisson if at all sick.


Report at once at the office all cases of illness, even if they occur after going home.

He next subjected every man to a physical examination, the idea being to exclude anyone suffering from heart or lung disease, anyone who struck him as too old for such work, and all obvious drinkers. Every new caisson man thereafter was required to have a work permit signed by him; and though only a few were actually rejected, the knowledge that an examination and a doctor’s permit were required doubtless discouraged many who were unfit from applying.

In any case, Smith was convinced that the men he cleared were in the best possible physical condition. He also saw to it that each man got a strong cup of coffee every time he came up out of pressure. “It appeared to relieve, in a measure, the nervous prostration which marked the return to open air,” Smith wrote. He did his best, too, to get the men to stay quiet a while after each shift, in a special resting room he had fitted out. But once out of the caisson, the next stop for most men was the handiest saloon. There the terrible, numb fatigue or the outright pain the work left them with could be cured considerably faster, they believed, than taking the doctor’s coffee or spending time on a company bunk.

The young doctor had no misconceptions about the off-hours recreation of the men or the living conditions most of them put up with. Many, he knew, slept in “lodginghouses,” as they were called, a damp cellar likely as not or one of the 14,872 tenements described in the 1870 census, where thirty people to a room was not uncommon, where the only light and ventilation came from a single passageway up to the street or to an ill-smelling common hall or kitchen. The ages of the men, as Smith noted, ranged from eighteen to fifty. They were of all nationalities, he found, but mostly Irish, immigrants who had known nothing else in New York but tenement life. The neighborhoods they went home to after a day in the caisson were famous as breeding grounds for measles, diphtheria, scarlet fever, the grippe. And in the teeming streets the one note of cheer was the saloon. “The habits of many of the men were doubtless not favorable to health,” Smith wrote, “but everything which admonition could do, was done to restrain them from excesses.”

Smith had been down in the Brooklyn caisson once or twice at Roebling’s request. And now again, as at Brooklyn, he noted with much interest that when the men spoke to one another in the heavy air it was with strange shrill treble voices and that it was physically impossible to whistle. (“The utmost efforts of the expiratory muscles is not sufficient to increase materially the density of the air in the cavity of the mouth, hence on its escape there is not sufficient expansion to produce a musical note.”) He noticed, too, that the men were breathing faster under pressure, and suspecting they were breathing harder as well, he wrapped a steel tape about his own chest, then compared the measurements he got when breathing inside the caisson and up on the surface. Under pressure, he found, his chest expansion was nearly twice what it was normally.

He studied the effect on circulation and discovered that while the normal pulse might rise sharply upon entering the caisson, after an hour or so it would drop back to normal or even below normal. The effect on the volume of the pulse was to diminish it. This, he thought, was caused by the pressure exerted on the artery. “Hence, the pulse is small, hard, and wiry.”

He observed that the men coming out of the caisson all had a marked pallor that lasted twenty minutes or so and that their hands were slightly shrunken and the tips of the fingers shriveled, as if they had been in water for a long time. Inside the caisson he took the temperatures of several workers and found they were one, even two, degrees above normal. The whole force was running a fever, he concluded, and told them this was caused by the heavy, saturated air, which kept their bodies from cooling by evaporation as they would normally. It was the reason they were always wringing-wet with perspiration, he explained. It was not that they were perspiring so much more, but that the air was not drying them in the least.