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<span class="chapeau">The Bourse de Commerce is surmounted by an iron dome constructed in 1813, designed by the architect François-Joseph Bélanger (1744–1818) with the assistance of his young colleague, Jacques Ignace Hittorff (1792–1867). During the historical study of the Bourse de Commerce that preceded the building’s restoration and repurposing, Pierre-Antoine Gatier discovered a group of drawings by Hittorff detailing the construction of the cupola, now in the collection of the Wallraf-Richartz Museum in Cologne.</span>
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<span class="alinea"></span>Nicholas Le Camus de Mézières’s radically innovative design of Paris’s Halle au Blé—stalls organized around a circular central courtyard—was constructed in 1764. The building was eventually altered to accommodate evolving needs: the open courtyard was covered, first by a wooden cupola, then with a cast-iron one, conceived in 1811 by François-Joseph Bélanger. His cast-iron cupola inaugurated the use of that material, a symbol of the new industrial era, in architecture.
<span class="alinea"></span>In his book <i>Building in France, Building in Iron, Building in Ferroconcrete</i><sup>1</sup>, Sigfried Giedion begins his account of construction in the nineteenth century with a chapter titled “The work of Bélanger and Brunet: the Halle aux Grains, Paris, 1811.” According to Giedion, the groundbreaking construction of this cupola marks the first instance of a modern collaboration between an architect, Bélanger, and an engineer, Brunet. Giedion saw this merging of compatible skills as an important exemplar, emphasizing the importance of teamwork among the members of the group formed by Bélanger, who each contributed to the creation of this cast-iron cupola. He also states that it was through working with Bélanger that Hittorff mastered the basic tenets of iron construction. Michael Kiene, professor at University of Cologne and a specialist in the work of Jacques-Ignace Hittorff, also highlighted the significance of this innovative collaboration between architect, engineer, and other associates “to create this complex cupola, whose originality would make it an important political symbol<sup>2</sup>.”
<span class="alinea"></span>Hittorff, who became one of the great architects of Paris during the Second French Empire (1852–1870), played a key role in this construction, which he directed on-site under Bélanger’s supervision. Through our research, we were able to produce an exceptional account of his participation, relying heavily on a collection of little-known drawings in the collection of the Wallraf-Richartz Museum in Cologne, containing 240 sketches of the cupola of the Halle au Blé. Thanks to an agreement between the Pinault Collection Paris and the Wallraf-Richartz Museum, these fragile drawings were carefully inventoried, researched, and restored. Most are signed by Bélanger, including seven also endorsed by Brunet in his role as “supervisor of construction at the Halle.”
<span class="alinea"></span>The collection consists of preliminary drawings and technical drawings used during the construction and assembly of the cast-iron elements. One remarkable drawing testifies to the group’s first reflections on the design: it shows cross-sections of the dome, comparing the use of cast iron and wrought iron for the project. Once the choice of material has been made, several more drawings illustrate the production of the cast-iron elements of the cupola, detailing precisely the geometry of each piece, then how those were assembled. These are addressed to the Le Creusot metal forge, which cast all the elements. These documents were extremely helpful in determining how to restore the framework of the cupola, as they revealed previously unknown information— for instance, the cupola is actually a composite structure of both cast iron and wrought iron. Further drawings detail the organization of the construction site itself, including the scaffolding.
<span class="alinea"></span>To obtain a complete picture of the construction of the dome, this newly found collection of drawings must be studied and compared with sketches in the collection of the National Archives: drawings by Bélanger and by Hittorff, by a rookie architect and by an established visionary, both participating in the conception of this unique dome, now considered a symbol of modern architecture. This collection confirms Sigfried Giedion’s intuition: that the cupola, by inaugurating sophisticated work methods that would be further developed throughout the twentieth century, announced the start of a new modernity.
1 — Sigfried Giedion, <i>Bauen in Frankreich, Bauen in Eisen, Bauen in Eisenbeton</i> (Leipzig: Klinkhardt & Biermann, 1928).<br>
2 — Michael Kiene, <i>Jacques Ignace Hittorff, précurseur du Paris d’Haussmann</i> (Paris: Éditions du patrimoine, 2011).