I have always been fascinated by great works of engineering – and especially by the idea of engineering under difficult circumstances – underwater, for instance. To this day I wonder at how wind turbines and harbours are constructed out at sea.
Well, I’ve been reading the rather good mystery novel The Interpretation of Murder by Jed Rubenfeld, which takes as its starting point Sigmund Freud’s visit to America in 1909:
“In 1909, Sigmund Freud, accompanied by his then disciple Carl Jung, made his one and only visit to the United States, to deliver a series of lectures on psychoanalysis at Clark University, in Worcester, Massechusetts. The honoury doctoral degree that Clark awarded him was the first public recognition Freud ever recieved for his work. Despite the great success of this visit, Freud always spoke, in later years, as if some trauma had befallen him in the United States. He called Americans ‘savages’ and blamed his sojurn there for physical ailments that afflicted him well before 1909. Freud’s biographers have long puzzled over this mystery, speculating whether some unknown event in America could have led to his otherwise inexplicable reaction.”
I won’t give away the plot of this rattling good yarn, but I will tell you that the construction of the Manhatten Bridge comes into it:
“The Manhatten Bridge, nearing completion in the summer of 1909, was the last of the three great suspension bridges built across the East River to connect the island of Manhatten with what had been, until 1898, the City of Brooklyn. These bridges – the Brooklyn, the Williamsburg, the Manhatten – were, when constructed, the longest single spans in existance, extolled by Scientific American as the greatest engineering feats the world had ever known. Together with the invention of spun-steel cable, one particular technological innovation made them possible: the ingenious conceit of the pneumatic caisson.
“The problem to which the caisson responded was this. The massive support towers for these bridges, necessary to hold up their suspension cables, had to rest on foundations built underwater, almost a hundred feet beneath the surface. These foundations could not be laid directly on the soft riverbed. Instead, layer upon layer of sand, silt, shale, clay, and boulder had to be dredged, broken, and sometimes dynamited until one reached bedrock. To perform such excavation underwater was universally regarded as impossible – until the idea of the pneumatic caisson was hit upon.
“The caisson was basically an enormous wooden box. The Manhatten Bridge caisson, on the New York City side, had an area of seventeen thousand square feet. Its walls were made from countless planks of yellow pine lumber, bolted together to a thickness of over twenty feet and caulked with a million barrels of oakum, hot pitch, and varnish. the lower three feet of the caisson were reinforced with boiler plate, inside and out. The weight of the whole: over sixty million pounds.
“A caisson had a ceiling but no man-made floor. Its floor was the riverbed itself . In essence, the pneumatic caisson was the largest diving bell ever built.
“In 1907, the Manhatten Bridge caisson was sunk to the river bottom, water filling its internal compartments. On land, enormous steam engines were fired up, which, running day and night, pumped air through iron pipes down into the great box. The forced air, building up to enormous pressure, drove out all the water through boreholes drilled in the caisson’s walls. An elevator shaft connected the caisson to a pier. Men would take this elevator down into the caisson, where they could breathe the pumped, compressed air.
“There they had direct access to the riverbed and hense were able to perform the underwater construction work previously considered impossible: hammering the rock, shovelling the mud, dynamiting the boulders, laying the concrete. Debris was discharged through ingeniously devised compartments called windows, although one could not see through them. Three hundred men could work in the caisson at one time.
“An invisible danger lay in wait for them there. The men who emerged from a day’s work in the very first pneumatic caisson – employed for the Brooklyn Bridge – frequently began to feel a strange light-headedness. This was followed by a stiffening of their joints, then by a paralysis of the elbows and knees, then by an unendurable pain throughout the entire body. Doctors called the mysterious condition caisson disease. Workmen called it ‘the bends’ because of the contorted posture into which its sufferers were driven. Thousands of workers had their health ruined by it, hundreds endured paralysis, and many died before it was discovered that slowing the climb back to the surface – forcing the men to spend time at intermediate stages as they ascended the shaft – prevented the disorder.”