The American bridge builder and engineer, David Steinman, speculates that nature did in fact provide the inspiration for the three major types of bridges—the corbelled arch, beam and suspension bridge, and that prehistoric man had found and used these. But one day a superman, who possessed extraordinary intelligence for his day, discovered that he was stranded without any of these bridges of nature to aid him at a time when he needed one badly. In a moment of brilliant thinking, he recalled the shape of such a structure—of, for example, the tree-trunk kind—and therefore he asked himself why he could not make or creates such a span. Over a century earlier, Thomas Pope, writing his own history of bridges in the early nineteenth century, commented:
That Bridges were requisite in the earliest periods of time, we cannot doubt, from the knowledge we possess of the common operations of nature. Seas, Lakes, Rivers, Brooks, and Swamps, must have existed formerly as well as now; and man, in his common pursuits, must have invented means of surmounting these obstacles to his correspondence with his fellow man, and keeping up the chain of connexion so necessary to his existence, as well as to his gratification.
We know that certain natural bridges were formed, that sustained themselves by the geometric principles of the arch. Such bridges, as those formed in Virginia and Arizona , attest to the strength of the arch. We also may reasonably surmise that the first bridges were such simple structures. There remains evidence of the “clapper” (from the Latin, claperius, meaning pile of stones) bridges in England, primitive rocks arranged for passage over rivers. These first beam, or stringer, bridges, were formed simply by laying a flat stone or log on supports without need for complex mathematical calculations or resolution of engineering problems.
By the same token, ropes and vines were used for carrying people over ravines and canyons. Perhaps someone first swung from one point to another, and later kept the vine or rope attached to two points so that cargo or persons could slide along from one end to the other. Eventually, these supports would hold another vine or rope over which people would walk, ultimately becoming a “roadway” in itself. Such may have been the origins of the suspension bridge.
The Romans, while certainly not the originators of the arch (credit has been given to the Babylonians for that), can fairly be said to have perfected its application and principles. Some of the stone arch bridges built by Roman engineers survive to this day.
So the allure of the bridge, beyond metaphorical and aesthetic attributes, is also attributable to their inherent link with the past, and their presumed link to the future. A bridge has a name, and that name connects it to other people and places. A bridge has a history, surrounded by ghosts. A bridge is part of the landscape. And bridges become part of our cultural awareness. It is impossible to think of New York without the George Washington Bridge, or San Francisco without the Golden Gate Bridge. The contemporary engineer/author Henry Petroski links them to their cities, calling them their “symbols and souls” in his book Engineers of Dreams.
These remarks are taken from my book, The Bridges of New Jersey, which is available in bookstores and from amazon.com and barnesandnoble.com.
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