America's Covered Bridges. Ronald G. Knapp
Чтение книги онлайн.
Читать онлайн книгу America's Covered Bridges - Ronald G. Knapp страница 14
Although Palmer’s early bridges all crossed the Merrimack River in Massachusetts, his fame spread, and in 1796 he was commissioned to build what was later known as the Chain Bridge over the Potomac River two miles above Georgetown at Little Falls. Chartered in 1794, the company hired Palmer and Jacob Spofford to build a multi-span bridge with a roadway that ascended and descended over each arched truss span. The longest was described as being 130 feet long with two additional spans that were shorter. Benjamin Henry Latrobe (1764–1820), a traveler from England, said it had been “framed in New England of white pine & brought hither by water,” suggesting that it was prefabricated, probably in Massachusetts, and shipped by water (1905). After its opening in 1797, it is said that George Washington routinely crossed it on the way to Mount Vernon. A critical French visitor wrote that it was “disgusting in its heaviness, having an immense quantity of timber and iron wasted on it” (La Rochefoucauld-Liancourt and Neuman, 1799). Not knowing that the bridge had already decayed and collapsed in 1804, Palmer wrote in 1806 that “the bridge I built over the Potomac at Georgetown in 1796 is not safe for heavy teams to pass over” (quoted in Peters, 1815). The Georgetown Bridge Company, owner of the crossing, duplicated the original, but only six months later a spring freshet destroyed the bridge. The third bridge, a chain suspension bridge, which gave the crossing its name, was built by James Finley (1756–1828) of Pennsylvania and John Templeman of Georgetown in 1807–8.
In 1794, Palmer and Moody Spofford built this great bridge from Haverhill to Bradford, Massachusetts, over the Merrimack River. Each of its three spans was 182 feet long, over 30 feet wide, plus a short drawspan that allowed ships to pass. This photograph, taken during demolition in 1875, shows something of its structure. (NSPCB Archives, R. S. Allen Collection)
Left uncovered until about 1825, the Haverhill Bridge received its open walkway on one side at a later date. (NSPCB Archives, R. S. Allen Collection)
A view of Palmer and Spofford’s Haverhill Bridge in the winter when the bridge’s floor would have been paved with snow to allow sleighs to pass. (NSPCB Archives, R. S. Allen Collection)
Originally built in 1795 by Palmer and Moody Spofford, the Rocks Village Bridge over the Merrimack, nearly 1,000 feet in length, lost two spans to a flood in 1818, these not being replaced until 1828. In this photo of the successor spans—none, apparently, the originals—an open turning bridge allows a sailing ship to pass. (NSPCB Archives, George B. Pease Collection)
Although more and more bridges were being built by this time, two stand out. One was a two-span arched bridge built uncovered by Captain Boynton between May 5 and November 21, 1797 over the Kennebec River at Augusta, Maine, for $27,000. The eastern span collapsed on June 23, 1816, but a new bridge was not built until 1818 when the western span was also replaced. The second bridge, the Lansingburgh-Waterford Union Bridge, a 800-foot-long four-span bridge over the Hudson River in New York State, is the first known work of Theodore Burr (see further discussion below). If Palmer was bold, Burr was brazen, for each arched span was around 200 feet long, with 18-foot-high arches, and two roadways. Opened on December 3, 1804, this was the first bridge over the Hudson and remained uncovered until 1814. When it burned on July 10, 1909, it was then the oldest wooden trussed bridge in the country.
By 1804, then, several builders had brought the science of wooden bridge construction to a surprisingly sophisticated level with many remarkable bridges and daringly long spans. None of them is known to have been covered with roof and siding, Peale’s assertion notwithstanding. Clearly, though, builders knew about covering bridges, but there was not yet general agreement on the benefits. None could deny, however, that in spite of tight joints, paint, or pitch, these glorious arches and trusses deteriorated if left open to the elements. The next step would lead to the creation of the first documented covered bridge in the United States.
Bridge historian Francis E. Griggs Jr’s concluding remark on the significance of Timothy Palmer’s Permanent Bridge in Philadelphia, the country’s first known covered bridge, sounds a bit hyperbolic, but within the historical context up to that point, he is likely correct: “. . . there is no doubt that Palmer had designed and built one of the most significant bridges in the world and maybe the most advanced wooden bridge ever” (2009: 516). Additionally, thanks to its location and the attention it garnered both in the United States and Europe, there is voluminous documentation, including diagrams, paintings, letters, and contracts, but alas, no photographs. Palmer, however, who later partially rebuilt and covered his 1792 Salisbury span over the Merrimack in 1807, wrote in a letter: “Last summer, I rebuilt one of the Arches; the span of which is 113 ft and is on the same principle with your Bridge” (Griggs, 2009: 513). Since there are photos of this bridge, we can more easily picture the much longer but more artistically finished Permanent Bridge.
Boston and Philadelphia were doubtless the two most important cities in the English Colonies at the time of the Revolution. During the revolutionary period, Philadelphia was the site for the signing of the Declaration of Independence, the writing of the Constitution, and the convening of the Continental Congresses. Following American independence, which was declared on July 4, 1776, and the final surrender of the British to General George Washington at Yorktown on October 19, 1781, Philadelphia continued to play a critical role as the seat of new national government, and from 1790 to 1800 it served as the temporary capital of the young United States while Washington, DC, was being built. In spite of a deadly outbreak of yellow fever, the city prospered, but its growth and communication with all points east were stymied by the Schuylkill River and the limitations of the ferry service first established in 1723. A movement to build a bridge on High Street, later called Market Street, began in 1750, but for numerous reasons—financial, technological, and political—only succeeded fifty-five years later when Palmer’s Permanent Bridge opened on January 1, 1805.
During this period, the best architectural and engineering minds of the city proposed numerous solutions. The first plan, submitted in 1767, was for a wooden bridge in a single arch some 400 feet in length and 47 feet above the water, but that proved unrealistic.
Two years later, on January 31, 1769, a Philadelphia architect named Robert Smith proposed building at least one wooden arched span, “. . . well covered to secure it from the Weather” (Griggs, 2009: 507). Though his proposal was ignored by the city assembly, it was the first known mention of covering a bridge in the colonies and foreshadowed Palmer’s Permanent Bridge. Another pioneering proposal appeared in 1774 when Thomas Gilpin of Philadelphia proposed building a suspension bridge with chains 400 feet long over the main channel approached by 300-foot-long abutments from each shore. Politician Thomas Paine, a man of many interests—both common and necessary in that day—proposed in 1786 both wooden and iron bridges, even building a 13-foot-long model of the iron bridge which he offered to Benjamin Franklin, who displayed it in his garden. The following year, Paine took that model to France, hoping for approval from the most highly respected bridge engineers in the world. Paine’s knowledge of iron bridges is all the more amazing considering that iron bridge technology had only just been introduced in England, first in a couple of obscure minor bridges and then prominently in Abraham Darby III’s amazing cast-iron bridge built over the River Severn in Coalbrookdale, England, between 1779 and