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Reviews
| American Bridge Patents: The First Century (1790–1890). Ed. by Emory L. Kemp, with essays by Emory Kemp, Shelley Birdsong-Maddex, Eric N. Delony, and Larry N. Sypolt. Morgantown: West Virginia Univ. Press, 2005. xiii+184 pp., illus., diags., notes. $40 pb (ISBN 1-933202-06-8).
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Patents are of unquestionable importance to the study and understanding of bridge engineering history. Both the lay public and professionals appreciate their relevance. Abba Lichtenstein (SIA), renowned bridge preservationist and civil engineer, always asks whether a certain bridge represents any patented technology in the course of rudimentary assessments of significance. The evaluation components of many state historic bridge inventories incorporate the concept, and patented technology can be a factor in applying the National Register of Historic Places criteria.
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Given their importance, an overview of 19th-century American bridge patents has been long in coming. American Bridge Patents claims to be "the most comprehensive collection of official bridge-patent information ever published" (p. 135). More than 600 patents are listed by date, name of the patentee, and patent classification.
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While it might arguably be the most complete published listing, it is certainly not the first. An early effort by F. B. Brock, a Washington, DC, patent attorney, appeared in a series of Engineering News articles during the early 1880s. Brock created "an illustrated historical description of all expired patents on truss-bridges" (Engineering News 9 [28 Oct. 1882]:371). They had become "public property" and were then available for use without a fee. While Brock began his 29-part series with a description and drawing of Theodore Burr's 1817 patent and ended with an 1866 suspension truss, its value extended beyond being a historic report. One Ohio bridge builder, Everett Sherman, read the October 1882 article describing the truss patented in 1846 by Horace Childs and shortly thereafter began specializing exclusively in its construction. Multiple examples of the Childs truss bridge built by Sherman still survive.
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A second, far more comprehensive listing was prepared by the commissioner of patents, M. D. Leggett, as part of a universal patent index in 1874. It included all bridge patents from 1790 through 1873. It listed patentees and their locations, dates, patent numbers, and descriptors of each design. Until the present volume, this listing was the sole shortcut for bridge patent research, although it obviously omitted the last quarter of the century.
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According to editor Emory Kemp, this new volume was assembled to help cultural resource professionals identify and evaluate historic bridges. More than simply a listing of patents, it incorporates four separate articles. The first essay, making up nearly half the volume, was written by Kemp to explain how "patents punctuate the history of nineteenth-century bridges" (p. 3). He provides a conventional history of the most widely used American bridge patents and their designers. The stories of Lewis Wernwag, Theodore Burr, Stephen Harriman Long, Ithiel Town, William Howe, Thomas and Caleb Pratt, Squire Whipple, Charles Ellet, Jr., and John Roebling are already widely known and appreciated. By treading this familiar ground, and occasionally digressing into European bridge history, Kemp has left unexplored other interesting and important elements of American bridge patent history. For example, patents had enormous promotional value and were aggressively sought by inventors, sometimes over a period of years. How was this broader concept of a patent adapted and utilized by bridge builders during the 19th century? If this essay emphasizes the most famous patents and patentees, what about the other patents that were less successful? Are there also good examples of and historical/technological lessons to be learned here? Surely, the study of hundreds of patents turned up some interesting inventions to describe and analyze.
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Continuing his story of 19th-century bridge history beyond well-known builders, Kemp describes the role of so-called "catalogue bridges," Pratt truss variations, masonry construction, and reinforced concrete. Here the connection to patent history seems oddly unfocused. Not until the discussion of reinforced concrete does the discussion return to the world of patents and competing inventions.
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Shelley Birdsong-Maddex worked on the study while employed at West Virginia University and prepared the essay on the development of the U.S. patent system. While the background of patent law and the governmental policy that accompanied it is invaluable, the essay lacked a clarity that would have come from paraphrasing instead of using numerous direct quotes from legal documents.
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The author of the third essay, Eric DeLony, will be familiar to most readers as the former director of the Historic American Engineering Record. He offers a personal account of his extensive background in and excitement with bridge patent research. Unfortunately, portions of his chapter unnecessarily overlap with Birdsong-Maddex's.
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This volume provides only limited patent data; it is meant to be a guide for those researching the patent office's database, accessed through its website. Larry Sypolt, another West Virginia University staffer, provides a detailed explanation of necessary procedures. For patents issued prior to 1975, there is no mechanism for searching the database text. Knowing the actual bridge patent number is essential, providing the main impetus for the book. The heart of this study is, therefore, the listing of more than 600 bridge patents, which makes up the last quarter of the volume. This list of patents is first sorted by date, beginning with Charles Willson Peale's 1797 design and ending with T. J. Hitson's 1898 suspension bridge. A second list arranges the patent numbers alphabetically by the patentee's last name.
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Several observations on the listings are in order. First, by ignoring the hometowns of the designers, which every patent application included, opportunities for comparative geographic studies were lost. Secondly, no cross-references were provided for patents with multiple designers, some of whom, like Job Abbott of the highly influential Wrought Iron Bridge Company, were quite important but do not appear as patent holders. Most fundamentally, however, this listing is selective, not comprehensive. Approximately 200 patents (DeLony makes reference to more than 800 patents in his essay) were left out. Some of the omissions were of patents included in Leggett's 1874 patent office index and that, in some cases, represent significant designs and structures. Most critically, no explanation is provided for selecting the "over six hundred bridge patents" that are included.
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Rather than speaking in generalities, some specific examples are in order. Assuming that the published 1874 index was comprehensive, then the new volume's most valuable contribution should relate to the last quarter of the 19th century. The patents listed on page 150, for example, include 25 designs issued between August 1875 and August 1877. A total of 18 bridge patents issued during that two-year period are not included. The omitted patents include five "safety-gates" for drawbridges, two methods for covering wooden truss members, a method for notching timbers to reduce decay, and a curious hydrostatic device for leveling segments of a drawbridge. These were all relatively insignificant inventions, and their elimination could probably have been justified, had the effort been made. Two were, however, legitimate pier designs, and four were truss bridges. One of the latter represents structures that were actually built, the design by the aforementioned Everett Sherman (patent no. 191,552). Another exclusion, an improvement in "metallic arch-bridges" (patent no. 184,490), was the work of Job Abbott, also mentioned above. Both Abbott and his company were celebrated for their designs in this area—all of which make the absence of these latter designs especially unfortunate. Beyond these chronological examples of omissions, it is noteworthy that neither of Edwin Thacher's concrete improvements (patents no. 570,239 and 617,615) is included in the listing, despite the citation of Thacher as a noteworthy reinforced-concrete builder in Kemp's interpretative chapter. Admittedly, all patents were not of equal value, nor can they be viewed as being of similar historical importance, but without an explanation of the selection rationale, readers will get an impression that the list is complete when it is not.
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Another goal of the publication was obviously to increase awareness of the watercolors prepared by designers as part of their original patent office submissions. Many are, indeed, spectacular, and West Virginia University Press has reproduced them handsomely, set off with contrasting black backgrounds. They have genuine artistic appeal, offering a tantalizing glimpse into the minds of these bridge builders beyond that provided by the standard specifications and drawings. The excellent production qualities of the volume are the primary recommendation for investing the purchase price.
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In addition to the volume's striking visual nature, editor Kemp deserves credit for the overall concept of its content. All the desirable parts are there: an overarching interpretative essay, an explanation of patent office history, a personal note on conducting patent research, an annotation on how to utilize the patent office's website, handsome graphics, and a lengthy listing of bridge patent numbers. Along with this well-deserved praise, he must also assume responsibility when the various components fall short of expectations.
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