To the Bridge

In my previous blog I described the feeling of swimming beneath the George Washington Bridge, the pairing of the mighty Hudson’s natural forces in perpetual ebb and flow and the stately, static grandeur of the human-engineered bridge. And I too was in motion at the nexus of the two, attuned with full sensory capacity to their majesty and interrelationship, witness to a linkage of two interdependent force fields.

Few structures embody a human-nature connection more than bridges. To state what is obvious though perhaps often overlooked as we become inured to these fixtures of transportation systems, bridges exist to overcome obstacles imposed by nature. Wherever a bridge exists, so too exists a natural feature that poses a challenge to humankind, whether it be a river, bay, wetland, or valley.  “Vaulting the sea”, as Hart Crane said in the poem, To Brooklyn Bridge.

Bridges are human-engineered solutions to connect areas whose separateness was eons in the making. They span gaping ravines created by forces of uplift and separation, valleys carved by glaciers, the steady erosive forces of rivers, and bays created by advancing seas.

The proportion, elegance, and mathematical symmetry of bridges embody laws of nature, defying gravity and load weight, whether from people, vehicles, or snow. Consider the compression-driven stability of arch bridges, where the weight of and atop the bridge is driven down to the ground, which in turn counters that force, and reinforces the bridge’s strength. So perfect are these structures that 2,000 year old Roman aqueducts still stand. Bridges range from the simplest wooden log across a stream or rope suspension solutions created by the Incas to traverse steep ravines, to the most sophisticated feats of metallic engineering.

Bridges can be regarded as a type of magic, erasing impediments created by nature. If medicine makes use of plant-derived potions to cure illness, bridges make use of human-leveraged natural laws of physics to overcome geographic features that separate places. They are transitional spaces, in equal parts a way to and a way from. Employing laws of physics--arches and suspension--and nature’s materials--stone, wood, and metal--bridges at once demarcate and erase the separateness nature has wrought and in so doing offer a hint of the uncanny.

Perhaps, then, it’s no wonder that folklore and myth are replete with disturbing creatures inhabiting watery edge-spaces: trolls, both helpers and troublemakers that first appeared in Scandinavian folklore and dwell under bridges or in other peripheral spaces; the fearsome and fanged multi-headed Scylla, transformed from a flirtatious maiden by Circe, and enemy of sailors passing by her in a narrow Mediterranean channel; or the dragon Grendel, describe in Beowulf as dwelling in a swamp at the edge of King Hrothgar’s kingdom.  

In the case of New York City, bridges span waterways whose origins date back hundreds of millions of years ago, when smaller continents collided into a supercontinent, which then rifted apart, creating a continental margin at what is now the Hudson Valley. Subsequent collisions, the absorption of a volcanic island arc, and the relatively recent (concluding 10,000 years ago) scouring of the land by glaciers carved the Hudson Valley further and left behind a moraine that shaped and created New York City’s bays and inlets, and even the Long Island Sound, flowing into the East and Harlem Rivers.

Bridges not only span the remnants of millions of years of geologic activity; they occasionally take advantage of them. The George Washington Bridge was built in its location, with the steep Palisades on the west side of the river and Washington Heights on the East side, in part to take advantage of the cliffs left in place by ancient geologic activity, which eliminated the need for lengthy approach ramps to avoid interfering with maritime traffic.

Spanning Newtown Creek, the Gowanus Canal, and the Hutchinson River; connecting City Island and Rockaway; and connecting Queens to the Bronx, Brooklyn to Staten Island and Staten Island to New Jersey, there are over 60 bridges in New York City. They range from arch bridges, to suspension bridges, to draw bridges, to one of four "retractable" bridges in the country. Manhattan is linked to neighboring boroughs and New Jersey by 20 bridges, the oldest of which, the High Bridge, which crosses the Harlem River and links the Bronx and upper Manhattan, was initiated by the need to transport water from upstate resources to the growing metropolis of Manhattan. Constructed in in 1848 as a stone arch bridge, the High Bridge looks like a Roman aqueduct. It took 35 years for the next bridge to be completed, the Brooklyn Bridge, a marvel of engineering that reinvented suspension bridge engineering by bundling multiple strands of steel cable, considerably enhancing the strength and load-bearing capacity of the bridge.

From simple to grand, crossing small creeks and powerful rivers, New York City’s bridges not only connect distinct locations. They also tell a story about the natural geography they inhabit.

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