Robert W. Passfield

Evaluating Authenticity: Reconstructed Timber Swing Bridges

When Parks Canada acquired the Rideau Canal in 1972 under a mandate to preserve its historic structures, there were five reconstructed timber swing bridges extant on the waterway. Subsequent research revealed that the design prototype for the timber swing bridge had been introduced on the Rideau Canal in 1866; that the bridges had evolved within a continuing traditional culture of conservation through replacement-in-kind reconstructions; and that the swing bridges had been reconstructed at 12- to 15-year intervals over the course of more than a century. This article evaluates the authenticity of the five reconstructed timber swing bridges within that particular cultural context to determine whether they were what they were purported to be—an evolved integral form of the original timber swing bridge that conserved the genuine heritage values that conveyed the significance and character of the original structure within its setting. In so doing, the article adapts and applies the test of authenticity, developed by the UNESCO World Heritage Centre at the Nara Conference on Authenticity (Japan, November 1994) to industrial archaeology and provides a case study of a new approach to industrial heritage evaluation that recognizes reconstruction as a legitimate conservation approach.

Introduction

When seeking to establish the heritage value of a cultural heritage property, a critical question emerges: is the monument or site what it purports to be? Is it authentic in terms of its claimed origin, character, or significance, given that cultural heritage properties evolve and undergo changes over time and that the changes, whatever they were, may not be identified or well-documented. Hence, there is a need to evaluate the authenticity of the cultural resource.

In heritage conservation, the traditional test of authenticity was applied to evaluate the condition of a heritage property in terms of its physical properties—design, materials, workmanship, or setting. The evaluation was based on the extant original material and the ultimate aim was the conservation of original fabric. However, at the Nara Conference on Authenticity, held in Nara, Japan, in November 1994, the World Heritage Centre, UNESCO, introduced a revised test of authenticity, based on a more anthropological conception of authenticity and heritage value that takes cultural diversity into account.

The Nara Document on Authenticity recognized that in seeking to conserve cultural heritage in its various forms and historical periods, authenticity could not be evaluated simply in terms of the physical attributes of a heritage property or in keeping with any fixed, universal standard. Different cultures have different cultural values that give significance and meaning to their heritage. Moreover, cultural heritage values are dynamic, not static; they can be intangible as well as tangible; and they might well be quite numerous and diverse. The cultural heritage values of a property can reside in its form and design, materials and substance, use and function, traditions and techniques, location and setting, and in the spirit and feeling of the environment of the setting, or any combination of these aspects in part or in total.

To evaluate the authenticity of a heritage property, the heritage values needed to be identified through sources that are credible, trustworthy, and complete; their meaning has to be understood within the particular culture in which the heritage property was created and maintained; and a determination has to be made as to where the cultural heritage values resided in the heritage property, inclusive of its setting. Once the "genuine heritage values" are identified, understood, and located, then the integrity of the heritage property can be evaluated to determine whether, and to what extent, genuine heritage values are conserved in the extant heritage property within its current setting. In that manner, the revised test of authenticity can be used to determine whether a heritage property is "authentic" in being what it purports to be.¹

Application to Reconstructions

As long as the older concept of authenticity prevailed, evaluating the condition of the physical properties of a cultural resource (original design, materials, workmanship, or setting), a reconstruction could not be authentic in the sense of being "true" or "genuine." A reconstruction, ipso facto, lacked the materials and workmanship of the original cultural resource. Once authenticity is conceptualized in terms of the conservation of heritage values, however, a reconstruction can be "authentic" to the extent that it conserves the genuine heritage values, both tangible and intangible, that conveyed the significance and true character of the original heritage property as defined within the culture in which it was created and maintained.² This is particularly the case for reconstructions carried out within continuing traditional cultures, such as the ritual rebuilding of religious shrines. Such reconstructions are an expression of a living traditional culture that conserves genuine heritage values, both in the reconstruction process and in the reconstructed cultural resource, inclusive of its original setting.³

This paper will adopt, adapt, and apply the revised test of authenticity to the field of industrial archaeology to evaluate the authenticity of five reconstructed timber swing bridges that were extant on the Rideau Canal in 1972 when Parks Canada acquired the canal and that had been conserved within a continuing traditional culture of replacement-in-kind reconstructions. The intent is to determine whether, and to what extent, the several reconstructions were "authentic" in conserving the genuine heritage values of the original design prototype within its setting.⁴ In so doing, the paper argues that reconstruction is a legitimate conservation approach and that the revised test of authenticity is applicable to industrial archaeology.

Sources

When a reconstructed structure is an evolved form of a culture resource that has undergone repairs, upgrades, and reconstruction(s) over time, there is an especially acute need to verify the credibility and completeness of the records documenting the earlier interventions and reconstruction(s). Fortunately, on the Rideau Canal the timber swing bridge reconstructions are well documented in departmental annual reports, maintenance records, official engineering correspondence, extant historic engineering drawings, and several historic photos. A photographic recording of the five reconstructed bridges extant in 1972 and a measured drawing record of one of the extant structures also exist. These sources, which are highly credible and trustworthy, span the entire period from the introduction of the design prototype on the Rideau Canal through 1972.

It has been documented that the original design prototype for the unequal arm center-bearing timber swing bridge was introduced on the Rideau Canal in 1866 and that, for more than a century, timber swing bridges were reconstructed at roughly 12- to 15-year intervals. Moreover, the sources enabled all of the extant reconstructions to be accurately dated: Jones Falls (1960), Brass Point (1964), Lower Brewer's (1967), Kilmarnock (1970), and Upper Nicholson's (1971) (see figure 1).⁵

Figure 1. Regional map, showing the locations of five reconstructed timber swing bridges extant on the Rideau Canal in 1972.
Drawing by Ken Watson, 2007.

Proposed IA Approach

Once the sources pertaining to an industrial monument, site, complex, or cultural landscape have been verified as credible, trustworthy, and complete, several steps have to be taken to evaluate the authenticity of an industrial cultural resource. First, as a preliminary step, the claimed significance of the cultural resource has to be clarified within its historical context, and then the test of authenticity can be applied to

identify and define the genuine heritage values that conveyed the significance and character of the original cultural resource, as well as any acquired heritage values of its evolved form, within the traditional culture (engineering or industrial) in which it was created and maintained;
locate where the genuine heritage values resided in the cultural resource as created within its original setting, and in the evolved form within its setting; and
evaluate the integrity of the cultural resource in its current condition and setting to determine its level of authenticity in conserving genuine heritage values.

In the present case, the significance of the original 1866 design prototype for the center-bearing timber swing bridge will be established through its historical associations; next, the genuine heritage values that conveyed its significance and historic character will be identified, defined, and located within the engineering culture and the environment of the setting in which it was created and maintained; and, finally, the integrity of each of the extant reconstructed structures within its current setting will be assessed to determine whether, and to what extent, it conserved and conveyed those genuine heritage values, by way of determining its authenticity (see figure 2).⁶ Throughout this whole process, the applicability of the revised test of authenticity to industrial archaeology will be assessed.

Figure 2. Jones Falls Swing Bridge, an unequal arm, center-bearing type of timber swing bridge as reconstructed in 1960. Photo by author, July 1974.

Significance through Historical Associations

None of the timber swing bridges on the Rideau Canal were associated with a historically important person, event, or important theme in Canadian history. The designer of the original design prototype, James D. Slater, superintending engineer, Rideau Canal (1858–1872), was not a distinguished bridge engineer. He was a competent engineer, a public servant with broad knowledge of bridge engineering, but he had no national reputation within that field. Consequently, the bridges have no heritage value through any association with a famous bridge builder.⁷

In 1925 the Historic Sites and Monuments Board of Canada declared the "construction of the Rideau Canal" was an event of national historic significance.⁸ The unequal arm, center-bearing timber swing bridges of the 1866 design prototype, however, were not associated with the construction of the canal in 1826–1832. They were not an integral part of a nationally significant construction event and have no heritage value through any association with that event.

Timber swing bridges were widely constructed on the Rideau Canal during the mid- to late-19th century but did not play a nationally significant role in the development of that region. It was the Rideau Canal as a water transport and waterpower system that fostered the settlement and economic development of the Rideau corridor, supplemented in the latter half of the 19th century by railway transport. Until the "good roads" era of the 1920s, the demand for the timber swing bridge structure was primarily a product of the population growth within the Rideau corridor, with swing bridges serving as facilitators of transport and travel for rural residents seeking to cross the canal to the mills, villages, and wharfs along the canal that were oriented towards the waterway and shipping. Road transport was of a purely local significance.⁹ The swing bridges were not on a historically important transportation artery that fostered the development of a major region of the country and have no heritage value through any association with the development of the Rideau corridor.

The design prototype of the timber swing bridge was by no means highly innovative, nor did it represent a nationally significant adaptation in the history of Canadian bridge engineering. Although designed specifically for use on the Rideau Canal, the prototype was but a slightly revised version of a standard center-bearing timber swing bridge plan that the Department of Public Works had introduced previously on the St. Lawrence River canals system.¹⁰ When erected, the original structure was not recognized as an outstanding engineering achievement, nor has its evolved form acquired any recognition as having symbolic significance as a historic engineering landmark.¹¹ Yet, the unequal arm, center-bearing type of timber swing bridge was widely constructed on Canadian canals in the late-19th century.

Timber swing bridges were erected across navigable waterways in Canada from the early 1840s to the end of the century. In many areas of the country, swing bridges replaced ferries for transporting people and goods across navigable waterways. Timber swing bridges were far less costly to construct than fixed, high-level bridges on Canadian steamboat canals and navigable rivers. Because they had a level deck, swing bridges were far easier to cross for heavily laden wagons (or sleighs in winter) than was a high-level bridge with steeply inclined approach spans. Moreover, swing bridges provided an unlimited vertical clearance for steamboats and Great Lakes schooners. Swing spans were far easier to maintain and operate than other types of moveable bridges, such as the retractile and primitive double-leaf bascule types employed previously on some Canadian canals. The early types of timber swing bridge introduced on the Rideau Canal during the 1840s and 1850s (the rim-bearing and offset pivot swing bridge types) had a major drawback—they required two workers to swing them, whereas the center-bearing type could be swung easily by one worker.

Once introduced during the 1860s, the center-bearing type of timber swing bridge, compared to other contemporary moveable timber bridges, was found to be efficient, cost-effective, relatively maintenance free, and easy to operate. It quickly proliferated on Canadian canals and navigable waterways, eliminating many long, circuitous road connections. New areas of the country were opened for settlement and development along arterial roads no longer interrupted by navigable rivers and canals.¹² Following its introduction, the center-bearing timber swing bridge played a prominent role in the history of Canadian bridge building and in the historical development of the country, a prominence based on its engineering qualities.

Engineering Heritage Values

Historically, the significance of the center-bearing timber swing bridge on the Rideau Canal resided in its being representative of a common type of moveable canal bridge. It possessed a number of characteristics that made this bridge a superior structure to alternative types of canal bridges—characteristics that accounted for its rapid proliferation on Canadian canals and navigable waterways. Hence, there is a need to identify, define, and locate the heritage values that conveyed the engineering significance and superior character of the unequal arm, center-bearing type of swing bridge and that represented that common type of nationally significant structure.¹³

To that end, the design, form, traditions, techniques, materials, substance, function and use as well as the traditional location and setting of the original Rideau Canal design prototype of the unequal arm, center-bearing timber swing bridge will be examined. Its heritage values will be identified and defined within the context of the continuing traditional engineering culture of conservation through replacement-in-kind reconstructions that prevailed in Canadian bridge building and on the Rideau Canal during the 19th century.

Design

The essence of the prototype for the original center-bearing swing bridge was in its being an unequal arm (or bobtail) structure, balanced on a single cast-iron pivot on which it rotated horizontally. In being an unequal arm swing bridge, the long arm that crossed the waterway was counterbalanced by a heavier short arm on the heel of the swing span. The superstructure was strengthened by a truss on each side of the bridge, consisting of a vertical main post with stay rods emanating downwards to the side girder of the swing span (see figure 3).

Figure 3. Plan, elevation, and cross-section of the design prototype for the unequal arm, center-bearing timber swing bridge introduced on the Rideau Canal in 1866. Library & Archives Canada, NMC 43043, drawing detail, 18 June 1866.

Three key design features were characteristic of the unequal arm swing bridge and conveyed its working principles. One design feature was the "regulator" at the apex of the truss system, which was a cast-iron saddle housing a pivoting crank to which the stay rods were attached. It was designed to keep in equilibrium the tensile forces in the truss system. With any downwards deflection of the long arm of the swing span under a moving load, the regulator would rotate to relieve the stress on the loaded stays. In effect, the downwards deflection of the long span would cause a corresponding upwards deflection of the short span, which resulted in a slackness in the short span stay, enabling the regulator to rotate.

The regulator function was part of the basic design principle of the center-bearing timber swing bridge, which was a beam bridge rather than a truss bridge. The truss system was not designed to carry any of the dead or live load when the bridge was closed on the abutments and carrying road traffic. When closed, the swing bridge was a simply a continuous beam structure, balanced on the central pivot, that rested on an abutment at each end. The stay rod trusses were designed to function only when the bridge was swung open, to keep the end of the long arm from sagging when no longer supported on its abutment.

The second key design feature was the single central pivot on which the swing span rotated, with a concentric circle of balance wheels running on a circular track about the pivot assembly to keep the swing span from tipping when swung off its abutments (see figure 4).

Figure 4. Ironwork and machinery of the 1866 design prototype for the unequal arm, center-bearing timber swing bridge. Library & Archives Canada, NMC 43043, drawing detail, 18 June 1866.

The third key design feature was the counterbalancing of the bridge on a pivot beam over the pivot assembly through increasing the weight of the short arm, or heel span, to counterbalance the long arm over the central pivot.

All three of these features were present in the design prototype of the Rideau Canal unequal arm, center-bearing timber swing bridge. Moreover, as originally designed, the swing bridge was counterbalanced in three ways: through tapering the two girders of the mainframe to reduce their dimensions and weight on the long arm; by the additional weight of the corbel frame and employing heavier framing timbers in the short arm rather than in the long arm; and by utilizing counterweights placed in pockets built into the short arm, generally loose stone, scrap iron, or gravel.

The unequal arm, center-bearing timber swing design introduced on the Rideau Canal in 1866 was similar in its basic design features and working principles to the center-bearing timber swing bridge already in service on Canada's St. Lawrence River canals system and Welland Canal in that era. Hence, the three key design characteristics of the original Rideau Canal design prototype were genuine heritage values, representative of the engineering significance of the unequal arm, center-bearing timber swing bridge common on Canada's canals during the late-19th century.

Integrity: All five of the reconstructed swing bridges extant on the Rideau Canal in 1972 embodied the design of the original timber swing bridge in terms of its three key design features. The truss regulator was conserved as originally designed as was the central pivot and concentric circle of balance wheels, although the pivot assembly was of steel rather than cast iron. The superstructure was also counterbalanced on a pivot beam over the pivot assembly, and the counterbalancing was carried out in the same manner as in the original design prototype, with the exception that the two girders were no longer tapered for their full length.

A minor modification was in the anchorage design for the lower ends of the truss stay rods at the bridge girders. Beginning in 1964, a flexible stirrup anchor replaced the simple bolt used to anchor the stay rods to the bridge girders. Only the earlier Jones Falls reconstruction retained the traditional simple bolt anchor. The flexible stirrup anchor relieved the truss stay rods from any compressive force that might come into play with a reversal of stresses, such as could occur during a rapid load-slack cycle caused by a moving load passing rapidly over the swing span. It increased the efficiency of the original truss design, complimented the regulator function of the prototype and represented a continuation of the 19th-century empirical engineering tradition of making design improvements in response to observations of structure behavior once the bridge was in service. This modification was a compatible design that would come to possess an acquired heritage value. It was typical of improvements in efficiency of the original design prototype within the dynamic engineering culture of 19th-century bridge building on the Rideau Canal and elsewhere on Canadian canals and navigable waterways. Hence, in their integrity of design, the Rideau Canal reconstructions were fully representative of the unequal arm, center-bearing timber swing bridge, and they possessed an authenticity of design (see figure 5).

Figure 5. Brass Point Swing Bridge, showing the center-bearing timber swing bridge span reconstructed in 1964 and the novel stirrup anchor for the stay rods. Photo by author, July 1974.

Associated Design Values

On the Rideau Canal, design specifications governed the carpentry and paint finishes on the bridge. In the design prototype, the ends of the cap beam and pivot beam were rounded up; the ends of the toe and heel beams were rounded; and the corners on the main posts of the gallows frame were chamfered in keeping with the construction specifications. Otherwise, the timber swing bridge was bereft of any ornamentation. Such a finishing standard was characteristic of good carpentry practice and was representative of the carpentry finish of the center-bearing type of swing bridge constructed on Canadian canals and navigable waterways. The carpentry finish was a genuine associated heritage value of the center-bearing timber swing-bridge design.

Another associated design feature was its paint finish as conveyed in the specifications. On the Rideau Canal, the exterior woodwork of the timber swing bridges was painted a stone color—three coats of linseed oil-white lead paint and a top coat of stone color—and the ironwork was painted black, which was in keeping with the Department of Public Works paint standard and color preference for bridges.¹⁴ The paint finish was an associated heritage value of design, representative of the center-bearing timber swing bridge and was reproduced in the Rideau Canal design prototype.

Another design feature was the manual mode of operation. The essence of this design was a finely balanced structure rotating on a single, central pivot with a minimum of friction that could be easily swung by one person without employing any mechanical-assist mechanism.¹⁵ On Canadian canals, the center-bearing swing spans were swung by one person, usually by means of a simple push-pull bar handle on the heel of the swing span. Some bridge sites retained a crab/endless chain/pulley blocks mechanism, installed to work an earlier type of swing bridge. This was the case on the Rideau Canal where both the simple push-pull handle and the earlier mechanical-assist crab mechanism were used by a bridge tender or canal man to swing the bridge.¹⁶ An associated heritage value of design resided in the push-pull bar handle and the mechanical-assist crab mechanism, both of which were manually operated by one person.

Integrity: All five reconstructions extant on the Rideau Canal in 1972 conserved the carpentry finish that was representative of the center-bearing timber swing bridge and the original Rideau Canal design prototype. All of the reconstructions were authentic in conserving the associated heritage value residing in the traditional carpentry finish.

None of the reconstructions conserved the paint finish representative of the center-bearing timber swing bridge. All five reconstructions were painted with the traditional oil-based paint, but the stay rods were not painted black to match the original, and the woodwork was painted white, instead of a stone color. Moreover, at Lower Brewer's the woodwork was two-tone—white overall with a bluish grey on the heel section. The reconstructed timber swing bridges were not authentic in their paint finish.¹⁷

All five of the reconstructed timber swing bridges extant in 1972 conserved the associated heritage value residing in the historic manual mode of operation—either one or the other of the two modes representative of the center-bearing timber swing bridge and of that type of swing bridge when first erected on the Rideau Canal. At Jones Falls, Lower Brewer's, and Nicholson's, the push-pull bar handle was retained on the heel of the reconstructed swing span. At Brass Point and Kilmarnock, the crab/endless chain/pulley blocks system was in place. Only the simple push-pull bar handle conveyed in a fully intelligible manner the reason for introducing the new center-bearing swing bridge in place of the older rim-bearing and offset pivot structures that had required two people working a crab/endless chain/pulley blocks system to open and close.

Form

A heritage value resided in the basic form of the Rideau Canal design prototype that was representative of the superstructure of the unequal arm, center-bearing type of timber swing bridge. This form took its shape and delineation from the characteristic arrangement of the structural components of that structure type. The heritage value of form resided in the horizontal mainframe supported by a corbel frame mounted on a transverse pivot beam, the gallows frame mounted over the pivot beam, and the stay rod trusses on either side of the bridge. The high railing alongside the swing span was a component of its form but had a safety rather than structural function.

Integrity: All five of the reconstructed timber swing bridges extant in 1972 conserved the heritage value of the form, representative of the significance and character of the unequal arm, center-bearing timber swing bridge. Several modifications had been introduced over the course of a century of reconstructions to simplify the construction details and to upgrade the load-carrying capacity of the prototype. The modifications, confined to the interior of the structure, were not visible or readily noticeable and did not compromise the traditional form. The reconstructed structures conserved the unequal arm configuration, balance, symmetry, proportion, and lines of the form that was representative of the unequal arm, center-bearing timber swing bridge and of the Rideau Canal design prototype. The reconstructions were authentic in their form.

Without the introduction of interior structural modifications to upgrade the structure's load-carrying capacity, it would have been impossible to have kept the timber swing bridges in service and to justify their conservation through replacement-in-kind reconstructions. Ironically, the interior structural modifications enabled the swing bridge to be conserved on the Rideau Canal when structures of a similar design were eliminated in toto from the other Canadian canals because of inadequate design values in the face of evolving road traffic needs.¹⁸

Traditions

The particular culture within which a cultural resource was created and maintained defines its significance and character, and if that culture encompasses a living traditional culture of conservation through replacement-in-kind reconstructions, the continuance of that process would constitute a genuine heritage value, which contributes to the significance and character of a reconstructed cultural resource.

From the introduction of the center-bearing timber swing bridge on Canadian canals and navigable waterways in the 1860s, there was a tradition of conservation through replacement-in-kind reconstructions. In the traditional approach to bridge building, the basic rationale, as with the Japanese temple reconstructions, was to overcome the debilitating decay to which wood structures are subject over time. Rather than being sustained as a religious ritual, the approach arose and was sustained by an engineering culture within which the efficiency and economy of design and construction as well as the maintenance of function and use were ultimate values. During the 19th century, a replacement-in-kind reconstruction that replaced wood components and salvaged and reused metal components was the most cost-efficient and practicable approach to keeping a timber swing bridge in service.

As long as the old structure had performed its function with a reasonable degree of efficiency and structural quality timber was readily available at a reasonable cost, there was no desire to change the design, to introduce a new type of structure, or to introduce newer types of materials. Modifications were made only in situations where an upgrade was needed to enable a bridge to meet increasingly heavy live-load demands. Moreover, such changes, generally confined to the interior of the structure, made use of the same original material or a like construction material. This bridge-building tradition predated the introduction of the center-bearing timber swing bridge but was representative of the engineering significance and character of that common bridge type on Canadian canals and navigable waterways in the late-19th century.¹⁹

On the Rideau Canal, the bridges were maintained in service within a continuing traditional culture of conservation through replacement-in-kind reconstructions, and the continuation of that bridge-building process constituted a genuine heritage value that embodied and represented a continuance of a cultural tradition, contributing to its significance and character. Indeed, that heritage value had two aspects: a tangible aspect (the reconstruction that embodied it) and an intangible aspect (the continued reconstruction process in representing that living cultural tradition).

Integrity: Where the heritage value of traditions is concerned, all five center-bearing timber swing bridges extant on the Rideau Canal in 1972 were reconstructed within a continuing traditional culture of conservation through replacement-in-kind reconstructions. They were authentic both in embodying and representing the heritage value of the continuance of that cultural tradition.

Techniques

The mortise and tenon joinery technique of heavy timber construction was employed in framing the swing bridge design prototype on the Rideau Canal. That technique of heavy timber framing was common in medieval Europe and widely used in 19th-century Canada in the construction of barns, houses, buildings, churches, mills, grain elevators, timber crib dams, wharfs, and canal lock gates as well as in the construction of center-bearing timber swing bridges on Canadian canals and navigable waterways. The technique of mortise and tenon timber framing was a genuine heritage value, representative of the unequal arm, center-bearing timber swing bridge.²⁰ In bridge building, mortise and tenon joinery began to be phased out in the mid-1880s when metal truss bridges were being introduced in large numbers, but it survived on the Rideau Canal for framing the reconstructed timber swing bridges.

Integrity: Three of the five reconstructed timber swing bridges extant on the Rideau Canal in 1972 were authentic in fully conserving the heritage value of the traditional mortise and tenon technique of heavy timber framing: Jones Falls (1960), Brass Point (1964), and Lower Brewer's (1967). This heritage value, however, was missing in the timber swing bridges reconstructed thereafter at Kilmarnock (1970) and Upper Nicholson's (1971). They were framed with butt joints and modern steel connectors and were not authentic in their framing (see figure 6).

Figure 6. Cutting up Lower Brewer's Swing Bridge, the last timber swing bridge framed with mortise and tenon joinery connections when reconstructed in 1967; the steel reinforcing angles were added in 1981. Photo by Eric Sunstrum, June 1984.

At Kilmarnock and Upper Nicholson's, there was also a new departure. The two swing bridges were reconstructed by contractors through a public tendering process, rather than by the Rideau Canal carpentry crew. Although this new development was a revival of an even older 19th-century practice, the contractors of the 1970s were no longer familiar with the traditional technique of mortise and tenon framing. An additional loss of an intangible associated heritage value occurred that was residing in the knowledge of the mortise and tenon framing technique that had been passed down through generations of carpenters in framing the bridges reconstructed on the Rideau Canal.

Materials

The heritage value of the materials representing the engineering significance and character of the center-bearing type of timber swing bridge needs to be carefully identified and precisely defined within the continuing traditional culture of conservation through replacement-in-kind reconstructions. Within that engineering culture on the Rideau Canal and historically in Canadian bridge building, decayed material was routinely replaced when it reached its active life expectancy by either the same type of material or a like material when the original material was no longer readily procurable or affordable. Historically, when the original structural material of the timber swing bridges, white oak, was no longer readily obtainable at reasonable cost in large-dimensioned structural grade timber, white pine was substituted. By the turn of the 20th century, when white pine became difficult to procure, Douglas fir was substituted. The wrought-iron rods and cast-iron fitting and machinery were salvaged and reused, but eventually all of the wrought- and cast-iron components were replaced with steel components of the same design.²¹

Function and continued use were the primary engineering values. In traditional conservation by replacement in-kind reconstruction, the original material and workmanship were readily discarded. Indeed, within that particular traditional engineering culture, the relative importance of original material and workmanship, as opposed to function and continued use, were the reverse of what they would be within architectural heritage conservation. The substitution of a like material when readily available at a reasonable cost was simply good engineering practice and was based on engineering values—efficiency and economy—in what today would be called an "engineering value" approach.

A genuine heritage value resided not in the conservation of original material but, rather, in the conservation of the same generic type of material—wood for wood and metal for metal. This heritage value was central to the replacement-in-kind reconstruction process in which the center-bearing timber swing bridges on the Rideau Canal, and elsewhere on Canadian canals, were created and maintained.²²

Integrity: The materials representative of the engineering significance and character of the swing bridge were conserved in the Rideau Canal reconstructions. All five of the reconstructed structures extant on the Rideau Canal in 1972 were authentic in their construction materials, wood structural members, and metal hardware and machinery as defined within the continuing traditional culture of replacement-in-kind reconstructions.

Substance

The essence of the unequal arm, center-bearing timber swing bridge on the Rideau Canal was in its being a massive structure composed of heavy, large-dimensioned timbers capable of carrying heavy loads over a clear span of almost 40 feet. The bridge was designed to carry heavy freight wagons loaded with grain, hay, manufactured products, and agricultural produce. The heavy structural timbers were the basic element defining the substance of the bridge's character and engineering significance. More generally, the massive structural timbers of the Rideau Canal bridge structures were representative of the substance of the center-bearing type of timber swing bridge on Canadian canals and navigable waterways in the late-19th century. The substance of the original swing bridge constituted a genuine heritage value. Any replacement of the massive structural timbers with smaller dimensioned members in a more modern material of greater strength would diminish the authenticity of the substance of a reconstruction.

Integrity: All five of the reconstructed timber swing bridges extant in 1972 conserved the heritage value that resided in the substance of the common unequal arm, center-bearing type of timber swing bridge. They conserved the heavy, large-dimensioned timber composition and massing of that type of traditional bridge structure and did so without any readily perceptible modifications in the dimensions of the structural members, their mass, or bulk. All five reconstructions were authentic in conserving the heritage value that resided in their substance and that contributed to their engineering significance and character.

Associated Workmanship

Traditionally in the heritage conservation field, workmanship constituted a primary heritage value, and the heritage value was held to reside in a static entity—the physical evidence of the workmanship of the creator or original builder(s) embodied in the fabric of the original structure. However, within a continuing traditional culture of conservation through replacement-in-kind reconstructions, wherein decayed material was intended to be replaced as a matter of course, the conservation of the physical evidence of the workmanship of the creator or original builder(s) was deemed of little, if any, value. What was of value was the continued employment of the traditional trade skills, tools, and trade knowledge when a structure is reconstructed and the realization of the same traditional high-quality standard of carpentry work in the reconstruction. Workmanship, as defined within that traditional engineering culture, is an associated heritage value that has both intangible and tangible aspects—intangible, in the continued employment of the traditional skills, tools, and trade knowledge; and tangible, in the quality of the finishing work as evidenced in the reconstruction.

On the Rideau Canal by 1960, if not somewhat earlier, modern power tools came to be used in reconstructing the timber swing bridges, and the traditional trade skills and hand tools were no longer employed. Moreover, with the reconstruction of the timber swing bridges at Kilmarnock (1970) and Upper Nicholson's (1971), the traditional mortise and tenon joinery was no longer used to frame the structural timbers. Contractors replaced the carpentry crews who traditionally reconstructed timber swing bridges.

Integrity: All five reconstructed structures conserved the tangible aspect of the associated heritage value of workmanship in their high-quality carpentry finish, representative of the character and significance of the center-bearing timber swing bridge on Canadian canals, but the intangible, dynamic component of that associated heritage value—the continued employment of the traditional trade skill, tools, and trade knowledge—was lost.²³ The constructions lacked integrity of workmanship and were not authentic in workmanship, as defined within the engineering culture within which the swing bridges were created and maintained.

Function and Use

Within the continuing traditional culture of conservation through replacement-in-kind reconstructions, the maintenance of bridge function and its continued use were the primary engineering values. The center-bearing timber swing bridges on Canadian canals and navigable waterways were conserved within that traditional engineering culture, and the conservation of function and use were genuine heritage values that contributed strongly to the historic character and significance of the bridge.

Integrity: All five of the reconstructed timber swing bridges extant in 1972 were authentic in conserving the totality of heritage values that resided in the function and continued use of the timber swing bridge. The reconstructed bridges conserved the function of the center-bearing timber swing bridge. They continued carrying road traffic across the canal and being swung open to pass canal vessels.²⁴

Location

The location in which a cultural resource was originally constructed can contribute strongly to its engineering significance and character, in being representative of the culture within which it was created and maintained. On 19th-century canals and navigable waterways, bridge engineers customarily located the center-bearing timber swing bridges at the narrowest section of a canal or the narrowest section of a canalized river or slackwater navigation. To provide a moveable span over the navigation channel, swing bridges were located either over a lock chamber within a lock station or in a multispan, low-level bridge crossing at the narrows of a canalized river or canal slackwater. This was invariably the case on the Rideau Canal and on Canadian canals more generally. When a timber swing bridge was reconstructed, it was in situ. Hence, the original location of a center-bearing timber swing bridge constitutes a genuine heritage value, contributing to its significance and character in being representative of the type of location in which the common center-bearing timber swing bridge was erected on Canadian canals and navigable waterways during the late-19th century.²⁵

Integrity: All five of the reconstructed timber swing bridges extant in 1972 conserved the heritage value residing in the location in which the original bridge was created and maintained. All were located in situ on the original road alignment. Four of the reconstructed structures were situated over a lock chamber within a lock station at the original bridge site. The reconstructed Brass Point Bridge was located in a multispan, low-level bridge crossing at the narrows of a small lake on a slackwater section of the canal where the original swing span was positioned. Indeed, all of the reconstructions possessed an authenticity of location (see figure 7).

Figure 7. Kilmarnock Swing Bridge, as reconstructed in 1970 over the lock chamber within the lock station. Photo by author, July 1974.

Setting

The physical setting in which a cultural resource was created and maintained—the cultural and natural landscape of the setting as well as its relationship to the surrounding landscape—can constitute a heritage value in contributing to its character and significance. This was particularly true of the unequal arm, center-bearing timber swing bridge that was constructed within the cultural and natural landscape of a canal setting. Once erected, it formed part of a distinctive canal bridge setting within the broader canal landscape. This was likewise the case on the Rideau Canal where the physical features of the canal bridge setting were representative of a 19th-century canal bridge setting.

The heritage value of the setting resided in the defining features of the canal cultural landscape and the natural landscape transformed earlier by the construction of the canal: the roadway crossing through the site and over the lock chamber where the swing bridge was located, the lock chamber, the raised water confined by canal embankments, the canal channel, and the auxiliary canal elements (lock master's house and lock office). Where a timber swing bridge was located on a river section of the canal, the heritage value of the setting resided in the roadway (the multispan, low-level bridge with a swing span positioned over the navigation channel) and the natural landscape transformed by the earlier construction of the canal in raising water levels as well as in the auxiliary buildings of the built environment (the bridge tender's shelter, and bridge tender's house adjacent to one end of the bridge). Thus, the physical setting in which the Rideau Canal center-bearing timber swing bridge was created, maintained, and reconstructed constituted a genuine heritage value.

Integrity: All five reconstructed Rideau Canal timber swing bridges extant in 1972 possessed integrity in their setting. The reconstructions were in situ, within a historic canal bridge setting wherein the composition, configuration, and defining features of the canal bridge site and the surrounding canal lands remained essentially as they were when the first center-bearing timber swing bridge was erected at Kilmarnock (1871), Lower Brewer's (1872), Upper Nicholson's (1877), Jones Falls (1883), and Brass Point (1887).²⁶ Some of the auxiliary components of the built environment had undergone modification, removal, or replacement over the years, but the defining physical features of the setting that conveyed the significance and character of the canal bridge site, within which the unequal arm, center-bearing timber swing bridge was created and maintained, remained unimpaired. The five reconstructions within their setting possessed an authenticity of setting.

Heritage Values in Environment

In evaluating the authenticity of a cultural resource, it has to be borne in mind that the environment of the setting in which the cultural resource was created and maintained has a psychic dimension as well as a physical dimension. There may well be intangible heritage values in the environment of the setting that contribute to a sense of authentic place, which can be conveyed by two distinct but related intangible heritage values:

the feeling that arises from the environment of the setting—in particular from the physical properties of the cultural resource within its setting and from the physical properties of the setting—in evoking a sense of stepping back into the particular time period and historic milieu that conveys the significance and character of the place wherein the cultural resource was created and maintained; and
the genius loci, or prevailing spirit of the setting, which permeates the entire environment of the setting and transmits meanings, patterns, and images that define the character and significance of the cultural resource within its setting, through conveying a sense of authentic place in terms of what it is.²⁷

Feeling

The physical environment of the canal bridge settings, wherein the unequal arm, center-bearing timber swing bridge was initially erected on the Rideau Canal and other Canadian canals during the 19th century, evoked a strong feeling of authentic place—the feeling of a 19th-century canal bridge site on a commercial transport canal. Moreover, that feeling was reinforced by the broader cultural landscape of the canal in which the defining features remained virtually unchanged from the time of its construction down through the years when the bridge was introduced and reconstructed in situ within the continuing traditional culture of conservation through replacement-in-kind reconstructions.

In 1967, the Historic Sites and Monuments Board of Canada designated "the entire lock system of the Rideau Canal including its locks, blockhouses, dams, weirs and original lockmasters' houses" as a place of national historic significance.²⁸ The Rideau Canal National Historic Site of Canada encompassed a corridor of 123 miles along the canalized Rideau and Cataraqui river systems between Ottawa and Kingston, Ontario, and constituted what today would be classed as a "defined cultural landscape," designed and created intentionally by humans. It comprises a linear cultural landscape in which engineering works formed and shaped the natural landscape to the point where the character of the canal and its significance as a cultural landscape are defined by the engineering elements embedded in the transformed natural landscape. In the physical environment at the canal bridge sites within that broader canal landscape, a strong sense of place conveyed a feeling of stepping back in time into a historic canal milieu—a 19th-century canal bridge site within a broader historic canal landscape. It was the case at the canal bridge sites within a lock station as well as on the slackwater sections of the canal, which continued to pass through rural areas largely free of modern intrusions.²⁹

The environment of the setting—the physical properties of the evolved form of the center-bearing timber swing bridge within its setting and the physical properties of the canal bridge setting—did evoke a strong feeling of authentic place. That feeling was an intangible heritage value that helped convey the significance and character of the center-bearing timber swing bridge within its setting.

Integrity: All five of the timber swing bridge reconstructions extant in 1972 when Parks Canada acquired the Rideau Canal were sited in the same location and setting as the original bridges at their own particular bridge site. Within the environment of the setting at each canal bridge site, the defining features of the cultural and natural landscape remained basically as they were when the first center-bearing timber swing bridge was erected there.

All of the canal bridge sites were located on county roads that crossed the canal in rural areas, were remarkably free of modern intrusions, and were physically isolated from the surrounding farming landscape by the tree-lined bluffs of the river valleys through which the canal passed. The only intrusions were early-20th-century upper story additions made to the lockmaster's house at Kilmarnock and Lower Brewer's adjacent to the canal bridge crossing and a heritage-style lock office built in the late 1960s beside the lock at Upper Nicholson's, adjacent to the timber swing bridge crossing over the lock chamber. Otherwise the only discordant feature of the setting's historic environment was the manicured lawns of the canal bridge sites that added a pastoral element to what was originally the cleared, rough ground of a work site at the interface of water and land transport (see figure 8).

Figure 8. Upper Nicholson's Swing Bridge, a typical reconstructed timber swing bridge setting on the Rideau Canal, as seen at a later date. Photo by author, 1993.

The setting environment at all five of the reconstructed timber swing bridges extant in 1972 evoked, in its integrity, a strong feeling of stepping back into a 19th-century canal bridge site that contributed to the significance and character of the center-bearing timber swing bridge within its setting. All five reconstructions possessed a feeling of authentic place within their settings.

Genius Loci

The genius loci is another intangible heritage value that resides in the environment of the setting in which a cultural resource was created and maintained. It constitutes the spirit of a place that brings the environment of the setting to life as a dynamic living place, working place, or inhabited landscape. The genius loci transmits the patterns, meanings, and image, which gather together and organize the elements of the environment of the setting into a meaningful and intelligible whole within conscious or felt boundaries—a gestalt that transcends the meaning of the sum of its constituent parts. In so doing, it orients the visitor, conveys a sense of functionality and continuity, and manifests a traditional way of life that links the present with the past.

The genius loci is evoked by the physical properties of the cultural resource within its setting, the physical properties of the setting, and the dynamic activities carried on within the setting at different levels. By conveying the character and significance of the cultural resource within its setting, it transmits a strong sense of authentic place.

When the center-bearing timber swing bridges were erected on the Rideau Canal, and on Canadian canals more generally in the late-19th century, the canal bridge sites were working places on a commercial transport canal. A strong genius loci permeated the cultural and natural landscape of the canal bridge sites that was reinforced by the dynamic activities of the place: the canal workers operated the locks and swung the center-bearing timber swing bridge for the passage of boats; on the slackwater sections, the bridge tender swung the moveable span of a multispan, low-level bridge to pass boats through the natural landscape of the canal. On the Rideau Canal, the genius loci comprised a genuine heritage value that resided in the environment of the setting in which the swing bridge was created and maintained, inclusive of the work activities of the original setting and the function and use of the swing span that conveyed its significance, character, and representativeness, along with a strong sense of the spirit of authentic place.³⁰

Integrity: The intangible heritage value of the genius loci that permeated 19th-century canal bridge sites was conserved within the environment of the setting of all five reconstructed timber swing bridges extant on the Rideau Canal in 1972. The spirit of the place was conveyed by the highly meaningful and intelligible relationship of the reconstructed swing bridge and the roadway to the canal structures of the setting, the work patterns visible in the layout of the physical features of the canal bridge setting, and the continuation of the traditional work activities and function of the center-bearing timber swing bridge in continued use.

The reconstructed timber swing bridges were not static structures. They continued to carry road traffic across the canal and were swung to pass canal vessels. Moreover, all of the swing bridges were opened and closed manually in the traditional manner, either by a canal worker as at the Jones Falls, Lower Brewer's, Kilmarnock, and Upper Nicholson's lock stations or by a bridge tender as at Brass Point on a slackwater section of the canal.

Whether approached by road or on the waterway, the genius loci of the setting environment conveyed the dynamic character and significance of the canal bridge site, established its visible or felt boundaries, and conveyed the function of a 19th-century canal bridge site in a highly meaningful and intelligible manner.³¹ The integrity of the genius loci was conserved in the setting environment of all five reconstructed timber swing bridges, and the genius loci manifested a strong sense of authentic place.

Authenticity of the Reconstructions

All five of the timber swing bridges extant in 1972 when Parks Canada acquired the Rideau Canal were reconstructed on the basis of information sources that were credible, trustworthy, and complete. None of their components were based on conjecture. None of the reconstructions, however, conserved the totality of the genuine heritage values and associated heritage values that conveyed the significance and character of the original cultural resource and its evolved form within its setting.

All of the reconstructions conserved the heritage values that resided in the design (the three key design principles), form, materials, substance, and traditions, as well as in the function, use, location, and setting of the center-bearing timber swing bridge prototype, as identified and defined within the continuing traditional culture of conservation through replacement-in-kind reconstructions and the history of canal bridge building in Canada. Only three of the reconstructed structures—Jones Falls (1960), Brass Point (1964), and Lower Brewer's (1967)—embodied and conserved the heritage value that resided in the mortise and tenon joinery technique that was representative of the traditional framing method of the 19th-century swing bridge. The two more recent reconstructions—Kilmarnock (1970), and Upper Nicholson's (1971)—were framed with the steel connectors used in modern heavy timber construction. They failed to conserve the traditional mortise and tenon method of heavy timber framing, thereby losing the associated, intangible heritage value that resided in the continued application of the traditional trade knowledge of that construction technique.

Where the setting environment was concerned, each of the reconstructed timber swing bridges within its setting conserved the intangible heritage values of the feeling and genius loci of a 19th-century canal bridge site, both of which contributed strongly to a sense of authentic place.

None of the reconstructions conserved the intangible associated heritage value residing in the continued employment of traditional skills and hand tools in their creation, as all of them were reconstructed primarily with modern power tools. The associated heritage value of workmanship was conserved in the standard of the carpentry finish of all of the reconstructions, but the associated design value of the original paint scheme was missing. All of the reconstructions conserved the associated heritage value that resided in their manual mode of operation.

Upon evaluation through the test of authenticity, it is clear that three of the reconstructed timber swing bridges extant on the Rideau Canal in 1972—Jones Falls, Brass Point, and Lower Brewer's—had a high degree of integrity and a high level of authenticity in conserving the genuine heritage values of the original cultural resource within its setting as well as in conserving the heritage values acquired by its evolved form in being present in situ in the Rideau Canal setting for more than a century. Although they lacked several associated heritage values, they were an evolved integral form of the center-bearing timber swing bridge in conserving the totality of the genuine heritage values that defined the essence of its significance and character.³²

The other two reconstructions—Kilmarnock and Upper Nicholson's—were missing a genuine heritage value that contributed to the significance and character of the unequal arm, center-bearing timber swing bridge as a representative structure. They lacked integrity and were an evolved form with a lesser degree of authenticity (see figure 9).

Figure 9. Lower Brewer's Swing Bridge, an orthographic projection drawing of a later 1984 reconstruction, showing the evolved form of the unequal arm, center-bearing timber swing span. Drawn by Gaétan Forest, 1993.

All five of the reconstructed swing bridges were of historic significance in the great extent to which they conserved the genuine heritage values that conveyed the significance and character of the unequal arm, center-bearing timber swing bridge erected on Canadian canals and navigable waterways in the late-19th century. As such, they were representative to a large extent of a common type of structure that had played a prominent role in Canadian bridge building and in the historical development of the country. Moreover, as of 1972 they were the only timber swing bridges extant and in service on any Canadian canal or navigable waterway.

Conclusion

As adapted and applied to evaluate the authenticity of reconstructed timber swing bridges conserved within a continuing traditional culture of replacement-in-kind reconstructions, the revised test of authenticity of the UNESCO World Heritage Committee (based on the Nara Document on Authenticity, November 1994) has revealed its potential utility for application in industrial archaeology. The application of the cultural heritage values-based test of authenticity to five reconstructed timber swing bridges on the Rideau Canal entailed dealing with a rather daunting array of values for a case study. It has the virtue, however, of enabling the versatility and comprehensiveness of the test of authenticity to be explored more thoroughly than would have been the case if a single extant cultural resource had been evaluated for its authenticity.

The revised test of authenticity has proved to be well suited for application within industrial archaeology in its systematic approach to evaluating the authenticity of a cultural resource. In this case study, an examination of the historical associations of the unequal arm, center-bearing timber swing bridge on the Rideau Canal was undertaken to determine its significance. It was found to reside in its representativeness of being a common type of structure that played a prominent role in the development of a major region of the country in the late-19th century. Once its national significance was determined, then the revised test of authenticity was applied to determine whether, and to what extent, the reconstructed center-bearing timber swing bridges on the Rideau Canal were authentic in being truly representative of the character of that nationally significant common type of structure.

To that end, the heritage values that conveyed the significance and character of the common center-bearing timber swing bridge were identified, defined, and located within the traditional engineering culture and historic environment in which the bridge was created and maintained during its period of significance.

In seeking to define the cultural heritage values of the common type of center-bearing timber swing bridge, the precepts of design, form, materials, substance, use, function, traditions, techniques, location, and setting were examined. They proved highly useful and appropriate for defining and locating the genuine heritage values that conveyed the significance and character of the bridge, as did the precepts of feeling and spirit in defining the heritage values in the historic environment of the setting that contributed to its significance and character.

The culture-specific heritage values approach to the evaluation of authenticity provided a ready means of determining what was truly significant and characteristic of the common center-bearing timber swing bridge on Canadian canals and navigable waterways during the late-19th century within the traditional engineering culture and environment wherein it was created, maintained, and reconstructed. It also enabled the function and use of the bridge to be recognized as heritage values along with the reconstruction process and the feeling and spirit characteristic of the canal bridge sites. Moreover, the approach was flexible enough to enable the design improvement embodied in the introduction of the stirrup anchor on the evolved form of the center-bearing timber swing bridge to be recognized as an acquired heritage value. Most importantly, it enabled the conventional concepts of materials and workmanship to be redefined and understood in a different, more meaningful fashion that expressed the values of the traditional engineering culture within which the center-bearing timber swing bridge was created and maintained. To that end, it proved much more apt as a methodology for evaluating authenticity in industrial archaeology than the traditional architectural test of authenticity.³³

Traditionally in heritage conservation, the architectural concept of authenticity has prevailed, wherein the original physical attributes of a heritage property—its design, materials, workmanship, or setting—are evaluated for the particular time of its creation. The focus is on conservation of the original fabric, but with minimal intervention. Within that traditional architectural conservation context, reconstructed structures were, and are, deemed contemporary works with no a priori historic value. A reconstruction is viewed simply as an interpretive or educational tool.³⁴ With the revised test of authenticity based on cultural heritage values, a paradigm shift in conservation values occurs. The intention is no longer simply to conserve "what is" but, rather, to conserve the genuine heritage values, both tangible and intangible, that convey the significance and character of the original cultural resource, as identified, defined, and located within the traditional culture in which it was created and maintained. In such a conservation context, a reconstruction can have a high level of authenticity in conserving the significance and character of the original cultural resource, and hence a reconstruction can have historic value.³⁵

Whether evaluating a reconstruction or an extant industrial cultural resource, the cultural values based test of authenticity provides a highly useful, apt, and efficient methodology for determining whether, and to what extent, an object is authentic in being "what it purports to be." The revised test of authenticity of the World Heritage Committee merits consideration for adoption within industrial archaeology.³⁶

Acknowledgments

The author thanks the IA editor and three anonymous IA reviewers for their insightful comments, which have resulted in a much more sharply focused analysis and argument. Although the present evaluation of the authenticity of five reconstructed timber swing bridges extant on the Rideau Canal in 1972 draws heavily on the knowledge, experience, and insights gained by the author in evaluating the significance of historic engineering structures and sites while in the employ of Parks Canada, the views expressed are solely the author's and do not necessarily represent the views or heritage values of the Parks Canada Agency.

Notes

^1. This summary is based on the Nara Document on Authenticity as well as on the framing papers and discussion papers prepared for the Nara Conference on Authenticity. See Knut Einar Larsen, ed., Nara Conference on Authenticity in Relation to the World Heritage Convention (Paris: UNESCO World Heritage Centre, 1995).

^2. Literature references to an "authentic" reconstruction in parentheses or to a reconstruction "possessing the quality of being authentic" recognize only the original cultural resource as truly authentic. When a cultural resource has evolved over a long period of time through a series of reconstructions but still embodies and conveys the genuine heritage values that convey the essence of the significance and character of the original cultural resource within it setting, then the reconstruction in its completeness or integrity of heritage values is an "evolved integral form" of that original cultural resource.

^3. Jukka Jokilehto and Joseph King, "Authenticity and Integrity," summary of ICCROM Position Paper, presented in Amsterdam, Netherlands, 1998. During the Nara Conference, two examples of a continuing traditional culture of reconstruction were commonly cited: that of the Japanese, wherein wooden Shinto temples were dismantled and reconstructed of new materials at 20-year intervals as part of a religious ritual established for centuries past; and that of the Haida peoples of British Columbia, wherein wooden totem poles of symbolic or familial significance were continually reconstructed to conserve their cultural heritage values, while the originals were allowed to follow their natural life cycle through decay to ultimate destruction.

^4. The application of the revised test of authenticity to the five reconstructed timber swing bridges in this paper is solely the responsibility of the author and may not be strictly in accordance with how the World Heritage Committee would interpret its concept of authenticity or apply its test of authenticity. Although the Nara Document speaks of heritage properties, herein "cultural resource" and "cultural resource within its setting" will be used, for clarity and brevity, to be inclusive of industrial monuments, sites, complexes, and cultural landscapes. By definition, a cultural resource encompasses archaeological, traditional, and built environmental resources such as buildings, structures, objects, districts, and sites that have a perceived heritage value.

^5. The provenance of the design prototype for the unequal arm, center-bearing timber swing bridge on the Rideau Canal and its structural evolution through a succession of reconstructions from 1866 to 1972 is documented in Robert W. Passfield, "Design Evolution: Reconstructed Timber Swing Bridges on the Rideau Canal," Canal History and Technology Proceedings, vol. 26 (March 2007):1–41. The wide variety and diverse nature of the sources that can be used to document industrial cultural resources is conveyed in the references of this paper.

^6. This three-fold examination framework is a standard approach for evaluating the significance and character of cultural resources. The Federal Heritage Buildings Review Office in Canada uses a three-fold evaluation framework—historical associations, architecture, and environment—in evaluating and classifying federally owned heritage buildings to ensure that their heritage character is defined and protected. For this paper, the term engineering is substituted for architecture; however, for industrial sites, the use of technology as a category would be more appropriate.

^7. James Dyson Slater (1813–1876) served as superintending engineer, Rideau Canal, from 10 Jun. 1858 to 1 Oct. 1872. Previously he had worked as a land surveyor locating railways and canals. He was employed by the Department of Public Works as assistant engineer on the Welland Canal and later as assistant engineer on the Ottawa River Works where he was responsible for maintaining timber slides, timber crib dams, roads, and bridges ("Engineers Employed on Public Works, Canada, 1779–1891," Sessional Papers [Ottawa, Canada, 1891]; Ontario Land Surveyors Association, "J. D. Slater," Annual Report [1921]:129–30).

^8. Historic Sites and Monuments Board of Canada, Minutes, Ottawa meeting (15 May 1925):11. For an overview history of the construction of the Rideau Canal, see Robert W. Passfield, Building the Rideau Canal: A Pictorial History (Don Mills, Ontario: Fitzhenry & Whiteside, 1982), 184 pp., illustrated.

^9. On the economic development of the Rideau Corridor, see V. A. George, "The Rideau Corridor, The Effect of a Canal System on a Frontier Region, 1832–1898" (master's thesis, Queen's University, Kingston, Ontario, 1972), and the summary, pp. 222–25.

^10. Slater to F. Braun, Secretary, Department of Public Works, 7 Feb. 1865 and 28 Apr. 28 1865, RG12, Vol. 3596, file 4053–255, Department of Transport, Library & Archives Canada (hereafter LAC); and Rideau Canal, Design for Swing, Contract No. 2906, 18 Jun. 1866, Rideau Canal, V2/410, 1866, NMC 43043, Cartographic and Architectural Archives, LAC.

^11. The term "symbolic importance" denotes that the structure itself has attained a recognized public status as a historic landmark representing an outstanding engineering achievement, meaning the monument transcends its era and its particular locale. For example, in the U.S. the Brooklyn Bridge has symbolic importance as a national icon itself, representing an outstanding engineering achievement.

^12. When the Rideau Canal was constructed, five bridges were erected: three fixed, high-level bridges (Bytown, Burritt's Rapids, and Newboro); a rectractile bridge (Merrickville); and a double-leaf bascule bridge (Kingston Mills). Two types of swing bridges were introduced subsequently on the Rideau Canal—the rim bearing and the offset pivot—before the center-bearing type of timber swing bridge was introduced in the 1860s on Canadian canals by the Department of Public Works. On the proliferation of the center-bearing timber swing bridge on the Rideau Canal, which was typical of Canadian canals in the 1870s and 1880s, see Passfield, "Design Evolution," 15–17 (n. 5).

^13. The forgoing analysis of the historical associations of an engineering cultural resource that bestow national significance is based on the guidelines for "Historic Engineering Landmarks" in Historic Sites and Monuments Board of Canada, Criteria, General Guidelines, Special Guidelines for Evaluating Subjects of Potential National Historic Significance (Fall 2002). The HSMBC approach to evaluating the national significance of historic engineering landmarks is set forth in Robert W. Passfield, "Commemorating Historic Engineering Landmarks in Canada," International Engineering History and Heritage, Proceedings of Third National Congress (Reston, Va.: ASCE, 2001), 175–84.

^14. J. D. Slater, "Specifications of a Bridge at Upper Site [Manotick], Long Island," 16 May 1865, RG112, Vol. 3596, file 4042–235, LAC (see n. 10); and J. D. Slater, "Specifications for Swing Bridge at Brewer's Lower Mills," 11 Sept. 1872, File 4052–248, Vol. 1, Rideau Canal Records, Bridges & Tunnels, Lower Brewer's Bridge, Parks Canada, Ottawa. The carpentry and paint finish standards are part of the design specifications and are associated design heritage values to be conserved. Workmanship is primarily an intangible heritage value, concerned with how the work is done, although the quality of the work is evidenced in the reconstruction.

^15. Slater to Braun, 30 Nov. 1864 and 7 Feb. 1865, RG 43 B61, Vol. 2006, reel T-2469, Department of Railway & Canals, LAC (see n. 10).

^16. Slater to Braun, 7 Feb. 1865 (see n. 15). Ironically, during a recording trip to the Kilmarnock timber swing bridge in July 1974, it was noted that the ends of the chain of the crab/endless chain/pulley blocks operating mechanism were disconnected from the heel of the swing bridge. The bridge tender preferred to simply push on the heel of the span to swing the bridge open and to pull the span closed—the original historic mode of swinging the bridge.

^17. For the paint specifications, see Passfield, "Design Evolution," 9–10 (n. 5). The operating mode of the individual swing bridges was recorded in a photo survey in July 1974.

^18. Passfield, "Design Evolution," 26–27, 29–30 (see n. 5). The author can attest from his familiarity with Canadian canals that no timber swing bridges are extant anywhere but on the Rideau Canal.

^19. By way of definition, on the Rideau Canal "replacement-in-kind" is a type of reconstruction that encompasses the substitution of a similar or like material, such as another species of wood, for the original wood fabric in situations where the original material is no longer obtainable or affordable in large dimensioned, structural quality timber. In contrast, "replication" is a type of reconstruction where only exactly the same material, e.g., white oak for white oak, is used in replacing decayed original material.

^20. Passfield, "Design Evolution," 5, 36–37 (see n. 5). See also Thomas Ritchie, Canada Builds, 1867–1967 (Toronto: Univ. of Toronto Press, 1967), 160–67. The carpentry trade practice in constructing mortise and tenon connections is detailed in Thomas Tredgold, Elementary Principles of Carpentry: A Treatise (London: J. Taylor, 1820).

^21. Passfield, "Design Evolution," 5, 10–11, 17, 20, 26, 36 (see n. 5).

^22. In authorizing the substitution of a like material when the original material of construction was no longer available, the Rideau Canal engineers did not insist that the substitute wood had to be from the same genus of tree. For example, white oak is a deciduous hardwood, but the materials substituted for it were white pine and, later, Douglas fir, both coniferous (evergreen) softwoods. When necessary, the original type of wood was simply replaced with a different type of wood that had acceptable design values.

^23. Ashton Dale, 12 Jan. 2005, personal interview with author. Ashton Dale began work on the Rideau Canal in December 1934 as an apprentice timberman, repairing timber crib waste weirs and reconstructing timber swing bridges and lock gates. He became a carpenter in 1937 and was appointed a carpenter foreman in 1949, in charge of a bridge and lock gate building crew. He retired in April 1977 as the maintenance supervisor, Rideau Canal.

^24. Thereafter, the Jones Falls swing bridge, which was in an advanced state of decay, had to be taken out of service as a safety precaution. It was swung open, and the road crossing was closed. The bridge lost its heritage value of continued use but retained its heritage value of function as it remained capable of being swung. Subsequently, the swing span was removed from its pivot pier and placed on blocks nearby. At that point, it lost its capacity to function as a swing bridge along with that heritage value. The other four timber swing bridges were reconstructed by Parks Canada during 1978–86 within the continuing traditional culture of conservation through replacement-in-kind reconstructions. See Robert W. Passfield, "Reconstructing Timber Swing Bridges at Parks Canada," Canal History and Technology Proceedings, vol. 26, (March 2007): 42–76.

^25. The terms location and setting are engineering values in that they were determined by engineering considerations relating to where and why a crossing was required and what the best siting was for the structure. They reflect heritage values that convey engineering significance and character. The heritage values of feeling and spirit reside in the setting environment.

^26. The fixed timber, pony truss spans of the Brass Point Bridge were renewed with steel pony truss spans on timber crib piers in 1903, yet the defining elements of the bridge were conserved—its form and basic design, scale and mass, the roadway and its alignment, and the moveable timber swing bridge span, not to mention its continuing function and use. The steel pony truss spans did not detract appreciably from the representativeness of that setting as a late-19th-century canal bridge site. The authenticity of setting was conserved at Brass Point to a large degree.

^27. The concepts of "sense of place" and "genius loci" as used here are derived from "The Concept of Place," pp. 27–38, and "Heidegger's Thinking on Architecture," pp. 39–48, in Christian Norberg-Schulz, Architecture: Meaning and Place, Selected Essays (New York: Electra/Rizzoli, 1988); and from Christian Norberg-Schulz, Genius Loci: Towards a Phenomenology of Architecture (London: Academy Editions, 1980). Although the genius loci is all pervasive in the environment of the setting in conveying a sense of place, it is not synonymous with the sense of place. A sense of place encompasses tangible heritage values embodied in the physical properties of the structure within its setting, the physical environment of the setting, and the intangible heritage value of its feeling; whereas the genius loci is a single intangible heritage value conveying the spirit of the place.

^28. Historic Sites and Monuments Board of Canada, "Rideau Canal," Minutes, Ottawa meeting (23–24 Oct. 1967): 17.

^29. The cultural landscape analysis of Rideau Canal is based on site visits and research conducted by the author in the mid-1970s as part of a project team that prepared site studies (what would now be called cultural landscape studies) of Rideau Canal lock sites. See Parks Canada, "Rideau Canal, Preliminary Site Study Series," 14 vols., Internal Reports, 1974–1977. See also a more recent study prepared for Parks Canada by a contractor: "The Cultural Landscapes of the Rideau Canal Corridor," unpublished report, The Institute for Heritage Education, Montreal, 1998, 397 pp.

^30. The strength of the genius loci in imaging the setting environment is dependent on the cultural perspective of visitors and their abilities to recognize the function and use of the cultural resource as well as to know its broader role and its historical and/or spiritual associations. The genius loci is perceived by the individual in experiencing the setting environment within which the cultural resource is situated.

^31. This analysis of whether the setting environment evokes a sense of authentic place is complicated by the fact that at the combined canal bridge/lock station sites, two layers of meaning are highly intelligible in a gestalt pattern. A visitor may see the image of either a canal bridge site with a timber swing bridge at its focal point or a canal lock station wherein one of the prominent features is a timber swing bridge. At Jones Falls the massive nature of the canal structures—four high-lift locks, a canal basin, a 62 foot high stone arch dam, and the high rocky banks of the river valley—overshadowed the canal bridge site, and, conceptually, the image of a canal lock station predominated.

^32. It is highly unlikely that any reconstruction, other than possibly a Japanese temple reconstructed in a traditional manner as part of a religious ritual, will ever be evaluated as an "authentic" reconstruction that fully conserves the genuine heritage values and the associated heritage values of an original cultural resource within its setting. The best that can be expected is that a reconstruction constitutes an evolved integral form of the original cultural resource within its setting, conserving the genuine heritage values that conveyed the essence of its significance and character, although lacking some of its associated heritage values.

^33. The nature of change in industry and the inadequacy of the traditional architectural concept of authenticity for evaluating industrial buildings, complexes, and landscapes, with its focus on original "design, materials, workmanship, or setting," is commented upon by Barrie Trinder, "Authenticity in the Industrial Heritage," Nara Conference on Authenticity (Japan: Agency for Cultural Affairs, UNESCO World Heritage Centre, 1995), 403–40.

^34. For example, Parks Canada does not recognize reconstruction as a conservation activity. The Parks Canada cultural resource management policy states that "the reproduction, reconstruction or replication of a cultural resource will be considered as an interpretative option, not as a conservation activity" (3.4.1.6); that "preservation encompasses conservation activities that consolidate and maintain the existing form, material and integrity of a resource" (3.4.3); and that "period reconstruction and reproductions are by definition contemporary work and have no a priori historic value" (3.5.2, subsection 6.3.5). Within the cultural resource management plan for the Rideau Canal, each of the four reconstructed timber swing bridges extant today is classified as a "noncultural resource." However, they are protected under the heritage preservation mandate under which the Rideau Canal is maintained and operated. (Parks Canada, "Cultural Resource Management Policy," Guiding Principles and Operational Policies [Ottawa 1994], 110, 114).

^35. Although generally reconstructions are not undertaken in industrial archaeology because of the heavy capital and maintenance costs associated with their scale and complexity, the legitimacy of reconstruction as a conservation activity still needs to be recognized.

^36. In its early years, industrial archaeology focused on the recording and conservation of industrial monuments—the icons of industry—that were associated with a great industrialist or engineer; a seminal event; or the introduction of a new technology, method of production, or material. The recordings were descriptive rather than analytical, were object focused, and were evaluated within the architectural concept of authenticity focusing on the "design, materials, workmanship or setting" of the object. At that time, the architectural concept of authenticity was not seen as posing any problem. This is no longer the case. See Marion Blockley, "The Ironbridge Gorge, Preservation, Reconstruction, and Presentation of Industrial Heritage," The Reconstructed Past, Reconstructions in the Public Interpretation of Archaeology and History, by John H. Jameson, Jr. (New York: AltaMira Press, 2004), especially pp. 177–81, 181–87. Blockley sees a need for a concept of authenticity that takes into account the dynamism of industry, the primacy of function, the nature of the evolution of industrial cultural resources, and the symbolic importance of industrial monuments.

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