Читать книгу America's Covered Bridges - Ronald G. Knapp - Страница 10
ОглавлениеNew Perspectives on North America’s Covered Bridges
Just think about it: you can still drive over (or, more properly, through) an all-wood covered bridge constructed as many as 180 years ago before bridge builders had even explained mathematically how bridges work. Over these years, the American covered bridge has passed through a series of phases, from its beginning as a common utilitarian river crossing to become a principal icon for an imagined, romanticized, and nostalgic past. As our perceptions have changed, so have our attitudes towards everything that affects the life of covered bridges, including “progress,” preservation, and re-imagination. While most Americans living east of the Mississippi or in the Northwest probably have seen a covered bridge, few besides a small body of enthusiasts have given them much thought. When examined in greater detail, covered bridges tell us much about our history, attitudes, ideas of progress, and sense of self. We seek to reflect about these matters in this book.
For those who simply enjoy visiting covered bridges, the rural or village setting, the rocky creek, or the chance to take some photographs of one’s children throwing stones into the water are sufficient attractions. For dedicated “covered bridge lovers,” however, there is much more to discuss and even debate. At one end of the spectrum are purists who desire that the bridges remain in their original condition, but at the other end are people who accept all manner of “preservation,” reconstruction, and alteration. The point where push comes to shove is in compiling the National Society for the Preservation of Covered Bridges’ World Guide to Covered Bridges, the edition of 2009 being the seventh (going back to 1956) and the official list of sanctioned covered bridges. Earlier editions began attracting controversy when they started listing some of the newly built covered bridges found on housing estates, private property, and in parks. These disagreements were a major reason why it took twenty years (1989–2009) to compile the latest edition, which now differentiates “authentic” covered bridges from ones deemed less authentic. In spite of the apparent agreement in the guide, not everyone is satisfied, and some argue for delisting of certain of the sanctioned bridges or adding ones that were omitted.
What is a Covered Bridge?
Defining a “covered bridge” would not strike most people as anything controversial. Is it not simply a bridge with a roof? But the discussion can raise hackles when questions of authenticity arise. For many years, the major divide was between those who accepted newly built, often undersized “fake” bridges and those who rejected them, at least with respect to including them in the World Guide or featuring them in Covered Bridge Topics, the National Society’s periodical. Today, the rapidly growing number of replicas—newly built copies—of original authentic bridges, where the original structure was either lost through arson, flood, or tornado or merely torn down and replaced by a new bridge using between a few and no original truss members, is creating new challenges. Resolving these questions turns on one fundamental question: how do we define a “covered bridge”?
If the descriptor—“covered”—defines the type, then any bridge with a roof and siding merits inclusion. But there are alternate ways to define the type as well. Some use the material as the critical element: the bridge must be all wood or a combination of wood and metal with wood dominating. According to this definition, then, stone arch bridges with wooden covers, often found in China, would not satisfy the criteria and would be excluded. For example, the now famous “Japanese Covered Bridge” in Hoi An, Vietnam, well known to thousands of Western tourists flocking to this UNESCO World Heritage City, does not qualify for inclusion since it is a pair of two small brick arches flanking a center span built on a stone slab, this base then covered with a small Buddhist temple.
Perhaps the most stringent definition is based on structure. To be “authentic,” the bridge must have a functional load-supporting truss system of some sort. As a consequence, “stringer bridges,” which have simple beams for support, do not qualify. Similarly, simple bridges having non-functioning simulated trusses also would not qualify. But excluding stringer bridges requires inconvenient exclusions because, here and there modest, homemade covered bridges have long been included in the “canon” of genuine entries, the World Guide. Delisting them after many decades will upset some.
Putnam County, Indiana’s Oakalla Bridge, which dates to 1898 and is a 152-foot Burr truss span, carries the light traffic of a classic country road. (A. Chester Ong, 2011)
A late example of the Paddleford truss, built in 1890, the Saco River Bridge sits within the town of Conway, New Hampshire, and remains open to traffic. (A. Chester Ong, 2010)
Although built late in the nineteenth century (1898), the Oakalla Bridge in Putnam County, Indiana, is a classic Burr truss typical of bridges built eighty or more years earlier. (A. Chester Ong, 2011)
Both to enhance the county’s long-running covered bridge festival and to provide a practical crossing, County Engineer John Smolen built the State Road Bridge in 1983 in Ashtabula County, Ohio, using a traditional Town lattice truss. (Terry E. Miller, 2006)
One of Smolen’s many “neo-traditional” bridges, the Caine Road Bridge, built in 1986 in Ashtabula County, Ohio, combines wood and steel to form a new version of the Pratt truss. (Terry E. Miller, 2009)
The Chua Cau (Pagoda Bridge) in Hoi An, Vietnam, usually called in English the “Japanese Covered Bridge,” has multiple stone arches and a wooden covered walkway along with a small temple over the water behind the bridge and entered from it. Built in the early seventeenth century by Japanese craftsmen who resided in Hoi An, the bridge is now an important part of this UNESCO World Heritage City. (Terry E. Miller, 2009)
Considering structure as the key factor also raises the question of which trusses are authentic. Some of the recently built “neo-traditional covered bridges,” such as Ashtabula County, Ohio’s State Road Bridge (35-04-58), built in 1983, make use of traditional trusses (in this case a Town lattice). But Ashtabula County has also constructed other new bridges using variants of the more modern Pratt truss (typical of metal bridges), such as the Caine Road Bridge constructed in 1986 and the Smolen-Gulf Bridge constructed in 2008. The Pratt truss is atypical among historical bridges, though not unprecedented.
Additionally, if having a “functional” truss is a requirement, then what about authentic bridges that have been reinforced to the point that the trusses, while present, no longer bear the load or merely support themselves and not the deck? When supports are added, these, rather than the trusses, support the bridge. Additional steel I-beams hidden beneath the deck to fully support the bridge render the trusses non-functional. By that standard, the 1894 Meems Bottom Bridge in Shenandoah County, Virginia, which was partially burned but could be saved and reopened supported by I-beams, would no longer qualify. The 1852 “double-barrel” bridge at Philippi, West Virginia, made famous as a battle site during the Civil War, is now a modern concrete and steel bridge housed over by the original trusses and roof and would also not qualify.
Less satisfactory is a definition that privileges age and date of construction. It is agreed that the “golden age” of covered bridges was the nineteenth century, but basing authenticity on age creates more problems than it solves. Virtually all of Oregon’s bridges were not only built after 1900 but continued to be built routinely into the 1950s. The same holds true for Québec and New Brunswick in Canada, where many bridges (all in New Brunswick) were built after 1900 and as late as the 1950s. Using date of construction as the determinant would also eliminate from consideration all newly cloned bridges, authentic in construction, but mostly built after 1990.
Ascertaining original intention is a difficult criterion. If the reason for building the covered bridge is purely pragmatic and functional, that is, as the best solution based on questions of efficiency and cost, then the bridge is arguably authentic regardless of age, truss, or material. Ashtabula County, Ohio’s Smolen-Gulf Bridge, dedicated in 2008 with Pratt trusses measuring 613 feet (making it the longest covered bridge in the United States, if accepted as authentic), was considered an appropriate choice by its builder, John Smolen. But do we wish to accept or reject this bridge based on the question of whether wood construction was cheaper than concrete and steel? And can we be sure that tourism was not a major factor in a county which features its covered bridges in an annual festival?
Building “covered” bridges for reasons of nostalgia or ambiance, especially with tourists in mind, would seem to exclude them based on the question of intention. This criterion makes it difficult to accept most of the new bridges, many of which might fail on other criteria as well. For example, the covered steel truss bridge in Ohio’s Mohican State Park, built for atmosphere rather than function, fails on several counts, including date, material, and intention. But can we be sure of the intention for (re)building Madison County, Iowa’s Cedar/Casper Bridge, whose original was burned by arsonists in 2002? When the county cloned the bridge in 2004 using its original plans, was it because this was the best solution for crossing Cedar Creek or because Madison County wished to maintain all examples of its greatest tourist draw—its covered bridges—based on the success of Robert James Waller’s novel, The Bridges of Madison County, and the movie of the same name?
Constructed in 1966 and the fourth bridge at this site since 1890, Lane County, Oregon’s Belknap Bridge spans the scenic McKenzie River. Although a typical Oregon Howe truss crossing, its late date of construction is slightly past the years when such covered bridges were still normal in Oregon, and Lane County’s reputation for bridges likely influenced the decision on replacement after its predecessor flooded out in 1964. (A. Chester Ong, 2012)
Meryl Streep, a war bride named Francesca Johnson, and Clint Eastwood, a National Geographic photographer named Robert Kinkaid, with Madison County, Iowa’s Roseman Bridge. The 1995 film The Bridges of Madison County was adapted from Iowa author Robert James Waller’s 1992 novel of the same name. For the film, county officials agreed to “age” the bridge to make it appear more rustic than its modern upkeep did. A Broadway musical based on the story will open in 2014. (Warner Brothers)
We could ask, what is the purpose for list making, such as the World Guide? What do readers (including those of this book) want to know? If the purpose is to list and discuss every known covered bridge in the land regardless of its attributes, multiple volumes might be required. If the list’s purpose is to identify only the strictly historical bridges, then it will be a rather slender volume. Would readers like to know about clones such as Kentucky’s Bennett Mill Bridge and the out-of-whole-cloth Town lattice State Road Bridge in Ohio’s Ashtabula County? Should they also know about the same county’s newest bridge, the gigantic Smolen-Gulf Bridge? I think most do. Further, should they know about Parke County, Indiana’s newly rebuilt Bridgeton Bridge whose burned original was central to the county’s covered bridge festival?
Built in 1858 over the Battenkill by Ephraim Clapp, the Eagleville Bridge in Washington County, New York, had to be restored in 1977 after suffering severe damage in a flood. (A. Chester Ong, 2010)
Crossing the Wallkill River just east of I-87 in Ulster County, New York, Perrine’s Bridge was originally built c. 1844–50 by Benjamin Wood using the Burr truss. After being closed in 1930, the bridge deteriorated until becoming dangerous in the early 1960s when restoration began. (A. Chester Ong, 2012)
Ultimately, it is up to the editors of publications listing covered bridges to set standards for inclusion. The World Guide is more problematic in that changes in policy could wreak havoc on each edition if new editors make major changes such as including or excluding all those “fake” bridges we love to hate. Designating a bridge with an official number (state-county-bridge) lends it legitimacy. Once a number has been assigned to a bridge, you cannot eliminate that listing or replace it without creating a certain amount of chaos.
We favor distinguishing “classic” historical bridges from those which are less so. But we also recognize that a full discussion of the covered bridge in America (including Canada) cannot take place without the inclusion of bridges that have been modified or even reconstructed. In many cases, the World Guide adds #2 to the bridge’s number. Indeed, let that be the thread that unifies the narrative: our changing perspectives on the covered bridge.
Eberly’s Mill Bridge, built in 1846 of Burr truss construction, is typical of Lancaster County, Pennsylvania. Though retaining a high density of Amish who continue using their horse-drawn buggies, as seen here, the county’s spectacular growth has altered its countryside from rural to suburban, forcing the Amish to live within urban development and congestion. (A. Chester Ong, 2011)
This three-span Howe truss deck railroad bridge crossed the Allegheny River at Foxburg on the western edge of Clarion County, which is north of Pittsburgh. Approached on both banks by long, curving trestles, the upper deck carried trains and the inside deck appears to have carried wagons, while a pedestrian walkway runs outside the trusses. Such structures came about in response to America’s growing industrialization. (Smithsonian Institution)
The last remaining covered canal aqueduct in the United States, Metamora, Indiana’s Duck Creek Aqueduct, was built in 1847 to replace an 1842 predecessor destroyed in a flood. Sixty feet long and of Burr truss construction, it carried the Whitewater Canal over Duck Creek for only a brief period. The 76-mile-long canal, built between 1836 and 1847, was so heavily damaged again by flooding in 1847 that little of it remained open. After falling into disrepair, the state restored the bridge in 1946, and today it carries tourists seeing the village of Metamora from a newly built canal boat. (A. Chester Ong, 2011)
The Juniata Division of the Pennsylvania Canal—actually a system—was opened in 1832. Starting from Duncan’s Island on the Susquehanna River, the canal crossed the Juniata River through a 600-foot multi-span Burr truss-covered aqueduct with interior towpaths. This canal branch, with 86 locks and 25 aqueducts, never made a profit, and the right of way was eventually sold to the Pennsylvania Railroad. (Pennsylvania Canal Society)
Built in 1838 by John Hough to cross the Scioto River, the Circleville Aqueduct was the longest covered aqueduct on the Ohio and Erie Canal. After the canal ceased operation in 1878, the bridge served as an ice skating rink in the winter and as a dance hall at other times until it burned under mysterious circumstances in 1915. (Miriam Wood Collection)
Bridge Basics
Covered bridges are essentially wooden (or mostly wooden) trusses that carry a roadway over a body of water. While most such bridges today carry (or carried in the past) vehicular traffic, many similar bridges also carried railroads. Less common were aqueducts designed to carry a canal and canal boats.
When the roadway passes between trusses whose base is level with the roadway, engineers call this a “through” bridge. When the roadway passes above the trusses, engineers call this a “deck” bridge. Because covered bridges by definition have a roof, all covered bridges are “through” bridges, but a great many wooden through truss bridges, especially those built for railroads, were left uncovered. Deck bridges could be covered in that the sides were protected with siding, but just as many were left open. Some deck bridges, sided or not, carried vehicular traffic, but the majority carried railroads.
Through bridges have the advantage of being higher over the water, and deck bridges, because the trusses are below grade, tend to be closer to the water and therefore more vulnerable to floods and ice jams. Aqueducts could be either through or deck, covered or uncovered. Some through aqueducts were fully covered. Through aqueducts, however, were necessarily quite wide to allow for towpaths on each side of the trough. Not surprisingly, the majority of aqueducts were deck trusses with the trough running between the upper portions of the trusses.
In addition to full-sized bridges and aqueducts, there are also “pony” truss bridges. Some are simply low trusses in an otherwise normal covered bridge, while others are boxed and lack a roof.
Bridge trusses had to be placed on some kind of foundation. Where stone was plentiful, these foundations consisted of large rectangular blocks laid without mortar. Where stone was difficult to obtain, builders often used heavy wooden posts, but foundations of wood naturally deteriorated quickly. The foundations on each bank of the river or stream are called “abutments,” while supports built between them in the river are called “piers.”
In most cases, the builders preferred to build the roadway right to the bridge entrance, sometimes held in place by stone parapets or retaining walls. In other cases, builders constructed free-standing abutments at the water’s edge and away from the higher river bank, requiring open wooden approaches.
Sometimes these approaches were supported by simple wooden trusses, either open or boxed in. While this solution provided the river a wider space during flooding, it made entering the bridge more dangerous for vehicles, and open wooden approaches naturally rotted quickly too. Open approaches are common in the American South and Midwest, especially Illinois and Iowa.
How the Book is Organized
The era of the covered bridge in North America spans slightly over two centuries. Chapter One views them both historically and as common sense, logical solutions to the problem of getting people, animals, and goods across rivers. They were simply bridges—utilitarian, functional, commonplace—although sometimes later recognized as engineering marvels or seen as aesthetically pleasing masterpieces.
During the first half century or so, roughly to 1850, bridge builders worked from their experience in constructing other kinds of wooden framed structures, especially houses, barns, churches, and mills. Although bridge building became a mathematically informed science during the second half of the century, with the appearance of several “treatises” and textbooks on bridge building, many local builders continued to work within local traditions based on an experientially learned body of knowledge passed down from elder to younger. Indeed, some local builders were illiterate, yet could construct wooden bridges capable of carrying heavy traffic for many years.
The covered canal aqueduct at Taylorsville, Ohio, after its partial collapse following the 1913 flood. Its Burr truss design is clearly visible. (NSPCB, R. S. Allen Collection)
Built in 1880 and restored in 1998, the Colvin (or Calvin) Bridge spans Shawnee Creek in Bedford County, Pennsylvania, with a half-size (or “pony”) truss. The upper chord is only halfway up, with the flared kingposts above it merely to support the roof. (A. Chester Ong, 2011)
Tohickon Creek is spanned by a 179-foot-long two-span boxed pony Howe truss in Bucks County, Pennsylvania’s Ralph Stover State Park. The short trusses are boxed in from the elements, but there is no necessity for a roof. (A. Chester Ong, 2010)
Rugged cut stone abutments and a pier support Maine’s Porter-Parsonfield Bridge between Oxford and York Counties. This 160-foot Paddleford truss bridge was built in 1876. (Terry E. Miller, 2010)
Like many bridges in the Illinois-Iowa-Kansas area, where streams are muddy and lack defined banks, Sangamon County, Illinois’s Glenarm Bridge sits on four metal cylinders filled with concrete, with short open approaches to the bridge. (Terry E. Miller, 1968)
A buggy emerges from an old and long-forgotten bridge over the Yocona River in Lafayette County, Mississippi, in the early 1900s. The Town lattice design was preferred in most parts of the South. (Lafayette County, Mississippi Genealogy and History Network)
Chapter Two traces the history and development of bridge design. At first using only the materials at hand—mainly timber but small pieces of iron hardware as well—bridge builders developed an increasing array of structural patterns—called “trusses”—which offered greater and greater flexibility, strength, and efficiency. Hundreds of bridge trusses were devised, many of them receiving patents, though practically speaking only about a dozen came into common use.
Chapter Three addresses a question that has long perplexed bridge enthusiasts: exactly how were covered bridges erected? After exploring several theories that have been proposed, we examine a body of evidence comprised of bridge treatises, personal reminiscences, and vintage photographs. We suspect that the answers have been difficult to come by because the methodology of bridge construction was simply taken for granted.
Chapter Four traces the fate of the covered bridge into modern times. As befell the canals and water-powered mills that developed during the same period as the covered bridge, new technology gradually rendered the covered bridge obsolete. As bridge building became an engineering science and foundries produced ever greater amounts of iron in ever larger pieces, wooden bridges gave way to metal bridges. As wood was giving way to metal, bridge building transitioned through a period of “combination” bridges in the 1870s to the 1890s, some being open, some covered. Oddly, though, the building of covered bridges did not end with the development of iron bridges. At the beginning of the twentieth century, when wooden bridges were mostly obsolete in New England, the Middle Atlantic States, and parts of the Midwest, two other areas began building covered bridges in great numbers—the American Northwest, especially Oregon, and the Canadian provinces of Québec and New Brunswick. Both areas were remote from iron foundries and steel mills in regions where wood was more plentiful. The American South, for similar reasons, continued building covered bridges into the 1930s.
In Bartow County, Georgia, travelers crossing the Lowry or Euharlee Creek Bridge first had to cross a wide flood plain on an open approach. While necessary, such structures were subject to rapid deterioration because of exposure to the elements. (A. Chester Ong, 2011)
This chapter also considers the period when covered bridges became, in most areas at least, obsolete, if not nuisances and impediments to progress. If covered bridges were well maintained, they remained capable of carrying most traffic, but increasing vehicle size and heavier loads created problems. Large trucks now carried freight, buses became heavier and larger, and farmers had tractors pulling larger and larger pieces of farm equipment over country roads. Another major change was the increasing use of school buses, especially when many small rural schools consolidated. To most people, especially those living nearby, covered bridges were considered simply old, obsolete, and “dangerous.”
While New Englanders generally valued their covered bridges as links to the past, elsewhere many people viewed them negatively. “Progressive” county officials pledged to replace them with nondescript, generic concrete and steel bridges fit for the modern times. In some areas, where officials were slow to discard the old bridges, local citizens forced the process by burning bridges. Although arson is a felony crime, relatively few of the culprits were caught, often on account of local politics where who you are trumps what you did. Throughout this time, floods, ice, windstorms, and other natural calamities also took a heavy toll, as they had been doing since the advent of bridge building. However, whereas in the nineteenth century when a bridge was lost to nature and would likely be replaced with a similar bridge, by this time the replacements were always modern.
Built in 1877 in Coshocton County, Ohio, the Mohawk Creek Bridge survived into the 1930s. Here, an early car emerges from the bridge. (Terry E. Miller Collection)
Groveton, New Hampshire (Coös County) prospered until its paper mill closed in 2008, and its bridge is now the town’s main attraction. Built in 1852 by Captain Charles Richardson using the Paddleford truss, the bridge served vehicles until being bypassed in 1939. In 1964–5, Milton and Arnold Graton refurbished the bridge. (A. Chester Ong, 2010)
Daredevil workers construct a Town lattice truss for a rail crossing during the winter. Unusually high trusses were required to support the extreme weight of locomotives and rolling stock. (NSPCB Archives, R. S. Allen Collection)
In 1901, when the Sebasticook River flooded, this covered bridge crashed against a new steel rail bridge near the river’s mouth in Winslow, Maine. (NSPCB Archives, R. S. Allen Collection)
Baptists baptize by immersion and they prefer moving water. Bridge sites were convenient, and baptisms could be held year round. Here, the Rev. Robert Colborn baptizes a convert around 1910 near the Stoutsville Bridge over the mostly frozen North Fork Elk River west of Stoutsville, Missouri. The structure, a Burr truss 145 feet long, was built in 1857 and razed in 1932. (Monroe County Historical Society [Missouri])
The Romain-Caron Bridge, built in 1940 at St. Jean de la Lande in Québec’s MRC de Tèmiscouata, is typical of the province’s standardized “colonization” Town lattice design. (A. Chester Ong, 2012)
Chapter Five examines covered bridges during our present time period, the late twentieth and early twenty-first centuries. With the elimination of most bridges vulnerable to nature or deemed nuisances, covered bridges have become much rarer than even just thirty years ago. But, as the covered bridge became increasingly associated with notions of “a simpler past” and attained the status of nostalgic icon, a number of counties around the United States discovered that covered bridges could draw thousands of tourists for festivals, bringing economic benefits to many, especially in places like Parke County, Indiana, which otherwise have little industry or economic activity.
By now, most covered bridges are well over a hundred years old, some up to 150 years, and fewer and fewer of them are up to carrying normal traffic. Whereas in the previous period, officials “progressed” by replacing the old bridges with modern ones, in this period every effort is made to keep the bridge “in some form” while still making engineering progress. In some cases, old bridges were bypassed and then became the responsibility of a park board or other entity as they sat in splendid retirement. Sometimes, however, the land and bridge reverted to the property owner, which unfortunately sometimes led to abandonment and deterioration. In many more cases, bridges were moved into parks, sometimes over water, sometimes not.
The greatest challenge currently to covered bridge aficionados is what is denoted as “restoration” or “reconstruction.” These terms mean different things to different people. The most conservative processes involve replacement of only the “bad” timbers, but defining “bad” is the issue. Traditional timber framers seek to keep all but the worst timbers in order to preserve the historical integrity of the bridge. Many “modern” engineers find little of the old wood to be serviceable. The question then becomes, at what point has a bridge’s historical integrity been compromised—with 40 percent new timber, 60 percent, or 80 percent? In quite a few cases, engineers simply replicated the old bridge using 100 percent new materials. When replacing a bridge that had been burned or destroyed, there is no choice. But when an historic bridge that remains in serviceable condition is simply dismantled and a replacement out of whole cloth put in its place, covered bridge lovers tend to become vexed.
Chapter 6 features fifty-five exemplary covered bridges in the United States and Canada, each with photos and an essay. Some are inimitable and exceptional, others are more typical. Each has something unique to offer: a colorful story, unusual construction, a special environment, or an object lesson. They are intended as a sampling rather than a “canon” of exceptional bridges.
With its open approaches removed, the 1858 Waldo or Riddle’s Mill Bridge in Talladega County, Alabama, isolated on tall stone pier-abutments, has been inaccessible perhaps since being condemned in the 1960s. Luckily, it survived the Civil War when a Union Army unit called Wilson’s Raiders crossed in April 1865. Several attempts to refurbish the bridge and develop a park have failed. (A. Chester Ong, 2011)
