Rowell's Covered Bridge, Hopkinton New Hampshire
The present Rowell's Bridge is the third of that name at the same site, and the only survivor of several covered bridges in the West Hopkinton area. The original bridge was in existence by 1793; on April 13th, 1803, the town voted to selectmen authority to repair Rowell's Bridge. On August 26th, 1845, it was voted to rebuild Rowell's Bridge "with such variation as to place as the judgment of the selectmen might indicate, said bridge to be built of stone, provided the cost should not be over $2500, and the builder would warrant the bridge to stand from three to five years after completion, the construction to be sold at auction to the lowest bidder." That bridge did not long outlive its guarantee, as it was demolished in the spring flood of 1852. On May 10th, 1852, the town voted to rebuild Rowell's Bridge of wood, with stone abutments; the selectmen were instructed "to make it of such a model as they deemed for the interest of the town, and locate the same accordingly." The new bridge was essentially complete by March 21st, 1853, for on that date the town voted to instruct the selectmen "to build a covered bridge across the river at Contoocook, like or similar to the one built at West Hopkinton the year previous, except to be with or without an arch, according to the discretion of the selectmen..."
The bridge itself, and the West Hopkinton area in general, has been known as Rowell's Bridge since early times; Abram (Abraham) Rowell emigrated to Hopkinton in the winter of 1786, and had a farm and mill near the present site of the bridge. The mill site was sold to John Smiley by 1835, but the farm remained in the family until 1899, when it was purchased by the Davis mill, the predecessor of the existing Hoague-Sprague mill east of the bridge.
From 1867 to 1899 a part of the Rowell house served as West Hopkinton's post office, as both Isaac Rowell and his son Charles were postmasters.
The bridge's only brush with disaster came shortly after it was built: a drove of cattle moved it off its abutments, but it was restored to place. Rowell's Bridge was repaired in 1947 by Judd Blaisdell; during construction of the Corps of Engineers West Hopkinton dam, just upstream, it was bypassed with a temporary steel military bridge erected parallel to it, in order to prevent damage caused by heavy construction equipment. In 1965 it was restored by the New Hampshire Department of Public Works and Highways State-Town Program.
The design is based on a Long patent truss but with integral solid Burr-type arches added by the builder, Horace Childs.
Although Childs built many Long-type covered bridges in the area this is the only one remaining locally, and one of the very few Long-type covered bridges still in existence.
Stephen Harriman Long was born in West Hopkinton, New Hampshire, in 1784. After graduating from Dartmouth College, he became an explorer and engineer with the U.S. Topographical Engineers and the U.S. Army. While head of governmental exploration between the Mississippi and the Rockies, he discovered the peak in Colorado which is named for him. Later, he explored the sources of the Mississippi; surveyed the Baltimore and Ohio railroad line; was the chief (topographical) engineer for the Atlantic and Great Western railroads; worked on the proposed national road from Main to Canada, and made improvements to navigation at the mouth of the Mississippi. When the Civil War began he was recalled to Washington, where he served until his retirement in 1863, at the age of seventy-nine; he died at his home in Alton, Illinois, the following year.
He is perhaps best known for his wooden bridge truss designs, patented in 1830, 1835 and 1839 (they are said to be the first American bridge trusses designed mathematically rather than intuitively, although his extensive biography in the Hopkinton history merely states, "He is said to have induced the construction of improved local bridges."
Long's patent design was based on a multiple kingpost with added counterbraces; his principal improvements over the Palmer-type truss were provisions for air space between stringer members; heavier end framing; a lighter lower chord; extra secondary chords and plates. Most significantly, Long's truss, like Town's, could be built by an ordinary carpenter.
Long was a bridge designer rather than a builder; he continued his experiments for thirty years, writing promotional leaflets and instruction booklets for bridge builders, building demonstration models which could be carried about in a case, and appointing agents who successfully competed for railroad, highway, and toll bridge contracts from Maine to Louisiana. Allen notes that the rival bridge promoters exchanged notes in the newspapers praising their own designs; Long's chief agent, his brother Dr. Moses Long, even used his free franking privilege (he was postmaster of Warner, New Hampshire) to send promotional material all over New England.
The Long and Town bridge designs were superseded by the Howe truss, invented in 1840, which was based on Long's design, but substitute adjustable iron rods for the vertical wooden posts. Long claimed patent infringement, but in vain: Howe's "improvement" was genuine, the first successful attempt to counteract the inadequacy of wood as a truss tension member. The Howe design led to the replacement of wood with iron and steel in bridge construction, and the eventual end of the covered bridge era.
Horace Childs, one of the pre-eminent New England covered bridge builders, was born in Henniker, New Hampshire in 1807 and died there in 1900. He was first a carpenter, but at the age of twenty three entered Hopkinton Academy to improve his education. He earned his way through school and boarded with his cousin, Col. Long, who at the time was living in Hopkinton while patenting his covered bridge truss designs. Horace became interested in Long's studies; Long encouraged him to become a covered bridge builder, and in 1834, having taken a contract to build a bridge over the Connecticut River between Haverhill, New Hampshire, and Newbury, Vermont, Long sent Childs to do the job.
Assisted by Long, Childs obtained contracts for railroad and highway bridges all over New England; his business was so successful that in 1846 his brothers Enoch and Warren joined him in partnership, using the name H. Childs and Company.
Enoch, a Yale graduate who had been a school principal in Montgomery, Alabama, was the designer and business manager; Warren, who also attended Yale, was the mason; Horace was the master builder. Using Long trusses at first, they went on to Howe, Pratt, Burr, and Town designs; in 1846, Horace patented a truss of his own design, based on a Long truss but with adjustable tension rods instead of counterbraces. (Horace's design was not widely used until the 1870s when a former New Hampshire man, Everett Sherman, built several Childs' truss bridges in Ohio. Of these, eight remain: seven in Preble County and one in Delaware County.
Injured in a railroad accident in 1853, Horace never fully recovered his strength; he continued for some time to build bridges, but finally retired to spend the rest of his long life in carpentry, farming and philanthropy. Warren retired at the same time, becoming a dairy farmer; Enoch continued to build bridges until he took a U.S. Customs position in 1860. Enoch's most famous single effort was the so-called Rainbow Bridge between Boscawen and Canterbury, New Hampshire; based on the McCallum truss, it had curved upper chords and roof.
Horace Childs' influence on covered bridge building in New England continued even after his retirement: his former employees, Frank Whitney and Dubey. Woods, became well-known bridge builders in their own right.
The circumstances linking Long, the Childs brothers, the bridge at Haverhill, and Rowell's Bridge would be worthy of detailed future research. Such research could possibly help to explain the presence of unusual Burr-type arches which Childs added to an otherwise straightforward Long truss at West Hopkinton. Since Childs had been taught bridge-building by LOng, where did he get the idea for the heavy arches which are, theoretically, superfluous to the Long panel truss. (Long's 1848 patent shows angled timber braces extending from secondary abutments to the top chord, but these diagonals are not arches.) While in Haverhill, could Childs have seen the 1832 Bath Bridge in nearby Bath, New Hampshire, and incorporated its Burr arches into his own later projects?
Bridge Description
Rowell's Bridge spans the Contoocook River at Clement Hill Road between Kast Hill Road and N.H. 127 at West Hopkinton, New Hampshire.
The bridge consists of one span, supported by two seventeen-panel trusses adapted from the Long patent, with added arches. The arches are significant because they are composed of solid rather than laminated timber segments, butted (some spliced) together. Integral with the trusses, they are mortised into the vertical and diagonal truss members, and through the chords: proof that they were not added later. More recently, the arches have been reinforced with iron plates just above the points at which they pass through the lower chord on the southern side.
Each truss has an upper and a lower multi-segmented chord composed of three parallel paired members, six in all, held apart by spacer blocks. The vertical posts, diagonal main braces and diagonal counterbraces are all doubled; the counterbraces lap over the main braces, which are flush with the verticals and mortised into the top and bottom, immediately below and above the upper and lower chords, respectively. The counterbraces and verticals are mortised through the top and bottom chords, so that their ends extend slightly beyond the chord edges in a spiky rhythm. The main braces are also mortised through the chords, but are cut off flush with the chord edges. The main braces are treenailed to the verticals, but all other connections between truss members are mortised, bolted, or both. (At the midpoint of the southern truss two vertical iron rods join the upper and lower chords; this is not repeated at the northern truss.) Many of the vertical and diagonal truss members have been repaired with through-bolted pieces of matching timbers.
The ceiling joists, spaced one per panel, rest on the top chords the connection is reinforced with single diagonal knee braces joining each joist to each vertical truss member. One set of upper lateral bracing is mortised together to form crosses between each joist bay; the braces are connected by alternate keys and wedges to the joists rather than to the truss chords. Some of the knee braces and lateral braces are replacements; horizontal iron rod reinforcing, forming random diagonals between the trusses, has also been added below the lateral cross-bracing.
Lower lateral bracing consists of a single diagonal member extending across each panel bay, zigzag fashion. At the points of intersection, an iron tie rod joins opposite stringers.
Floor joists, stiffened with wooden cross-bridging at thirdpoints rest on the stringers and extend beyond to hold the bottom edge of the siding away from the chords. The flooring is of timbers laid flat parallel to the chords and spiked to the floor joists.
The bridge abutments are built of 2'x4' split granite blocks, laid dry. The stringers rest on a continuous timber sill laid across the abutment, one course below its top edge; the arches bear on timber sill-blocks (compressed almost flat over the years) on a shelf below, an extension of the abutment, also laid dry. The arch ends are held apart by a heavy timber spacer which also rests on the shelf. The northwest ends of the arches have been reinforced with applied timber pieces bolted through the arches so that the actual arch ends are not visible. The bearing end of the applied timber on the south arch seems to be deteriorating, but the southeast ends of both arches are in good condition.
There are no lateral wing walls; instead, the abutments extend straight back onto the bank, parallel the trusses, to form a built-up approach to the bridge.
A most unusual feature of the structure is its central concrete pier. The bridge was built as a single span, but ca. 1930 or 19590 (sources differ) the pier was added to strengthen the bridge.
The result was the opposite of what was intended: the pier became a fulcrum and caused the bridge to seesaw under heavy loads, loosening its joints. Subsequently, the top of the pier was removed, leaving three feet of air between bridge and pier, which causes some concern among visitors unfamiliar with the bridge's history.
Rowell's Bridge is 167' long and 19'-8" wide, with a portal opening 15'-8" wide by 16' high. The base of the triangular gable spreads approximately 6' beyond each truss, making a total portal width of 28'. The roadway is 14'-10" wide (plus 5" low wooden curb-railings on each side), allowing two-way vehicular traffic. There is no posted legal load limit.
The upper three-fourths of the trusses are exposed; the lower exterior parts are sheathed with random-width flush vertical boards stained dark brown. The siding slopes slightly outward at the babe on the southwest side, but is completely vertical on the northeast side. At each end of the bridge, and at each side, there is a narrow buttress-like protrusion immediately over the river edge of the abutments below; these cover the ends of the timbers on which the stringers rest. The top edge of the siding is covered by a sloping sill, extending outward from the exterior face of the truss members. The interior sides of the trusses are protected from traffic damage by a 2"x12" wood handrail bolted to the truss members (and let in flush where they have been patched).
A medium-pitch gable roof covers the entire bridge, overhanging both the sides and the ends in order to protect the open trusswork. The gable ends are triangular, with an incised shallow semi-elliptical arch. The whole is outlined with a single flat trim board and is covered with horizontal narrow clapboards, of a faded grey-brown. The only other trim is a small flat square applied to the point where the corners of the arched portal openings meet the horizontal base of the gable. At each end of the bridge, the upper and lower chords of the trusses extend beyond the last panell; the upper chord projects beyond the lower chord, and is connected to it by doubled flared posts. The lower part of each of the posts is hidden behind three vertical 8" square wood bumpers, of the same height as the siding; those at the southeast are brown, while those at the northwest are painted white.
Because of the bridge's open truss construction, wide overhangs, and projected gables, the entire roof seems to float above the roadway.
The roof is framed with 4"x6" rafters, spaced one per joist, and cantilevered beyond the joist ends to form the considerable roof overhang. The rafters abut at the ridge, where the topmost purlin is mortised into the joint to form a ridgepole; the rafters are braced by verticals extending from each rafter to the joist below Exterior ends of the rafters are connected to the vertical truss members by diagonal braces sloping inward from the midpoint of the overhang in counterpoint to the kneebraces of the interior. The roof is covered with corrugated metal sheeting laid on purlins; the bottom purlin forms a continuous fascia.
The National Society for the Preservation of Covered Bridges World Guide to Covered Bridges number for Rowell's Bridge is 29-07-08; the New Hampshire Department of Public Works and Highways' number is 055/112; the New Hampshire Department of Resources and Economic Development number is 9.
Southwest truss of structure (1974)
