The Pantheon: From Antiquity to the Present Page 26

  Conclusions

  These calculations, however hypothetical in some aspects, serve to show that while the Pantheon may have been a triumph of construction, compared with other Trajanic projects including the emperor’s great thermae, or indeed the Temple of Venus and Roma, it was hardly the mammoth undertaking that many have wished to believe. Its Trajanic context reveals it not so much as the signature building of Hadrian the architect, or even of Hadrian the princeps, but as just the last in a series of outstanding and innovative building projects that characterize the reign of his predecessor Trajan.

  I am very grateful for the kind assistance of Christina Triantafillou, who worked with me on the basic calculations for the Pantheon, particularly for the grottoni and porch, and provided the key data on the Basilica of Neptune, all of which forms part of her unpublished doctoral thesis for the University of Oxford on the economics of Trajan’s building projects in Rome.

  1 Janet DeLaine, “The Romanitas of the Railway Station,” Uses and Abuses of Antiquity, ed. Michael D. Biddniss and Maria Wyke, Bern 1999, p. 150.

  2 See most recently Rabun Taylor, Roman Builders, Cambridge 2003, pp. 190–211; Gerd Heene, Baustelle Pantheon: Plannung, Konstruktion, Logistik, Düsseldorf 2004, p. 24; Lynne Lancaster, Concrete Vaulted Construction in Imperial Rome: Innovation in Context, Cambridge 2005, pp. 43–46.

  3 Janet DeLaine, “The Baths of Caracalla in Rome: A Study in the Design, Construction, and Economics of Large-Scale Building Projects in Imperial Rome,” Journal of Roman Archaeology, Supplement 25, 1997, pp. 103–109, 174–194.

  4 For example, M. E. Blake, Roman Construction in Italy from Nerva through the Antonines, Philadelphia 1973, p. 42.

  5 There is in fact no direct dating for the Basilica of Neptune. The 32 brickstamps identified in situ in the grottoni, as listed in Herbert Bloch, “I bolli laterizi e la storia edilizia romana,” Bullettino della Commissione Archeologica Comunale 64, 1937–1938, pp. 108–109, nos. 73–104, have often been erroneously attributed in scholarship to the Basilica (Christian Hülsen, “Thermen des Agrippa,” Römische Gebälke, ed. F. Toebelmann, Heidelberg 1923, p. 67 n. 3; Lanfranco Cordischi, “Basilica Neptuni in Campo Marzio,” Bollettino di Archeologia 5–6, 1990, p. 20 n. 56; Lise Hetland, “Dating the Pantheon,” Journal of Roman Archaeology 20, 2007, pp. 95–112; p. 99). The problem has arisen because of uncertainty in the origins and function of the basilica itself as either an independent structure or an element of the Baths of Agrippa, as well as in the relationship of the grottoni to the two structures. The grottoni brickstamps date to the same time as the Pantheon proper, the late Trajanic to early Hadrianic period. As far as can be seen, no brickstamps can be identified solely and specifically with the Basilica itself. However, unprovenanced brickstamps discovered in the general area of the grottoni and basilica all point toward a contemporaneous date for the two structures (see Bloch 1937–1938, pp. 109–112, for the list of brickstamps).

  6 E.g., Luca Beltrami, Il Pantheon: La struttura organica della cupola e del sottostante tamburo, le fondazioni della rotonda, dell’ avancorpo, e del portico, avanzi degli edifici anteriori alle costruzioni adrianee. Relazione delle indagini eseguite dal R. Ministero della Pubblica Istruzione negli anni 1892–93, coi rilievi e disegni dell’ architetto Pier Olinto Armanini, Milan 1898; Giuseppe Cozzo, Ingegneria Romana: maestranze romane; strutture preromane, strutture romane, le costruzioni dell’ anfiteatro flavio, del Pantheon, dell’ emissario del Fucino, Rome 1928, pp. 267–286; Kjeld De Fine Licht, The Rotunda in Rome: A Study of Hadrian’s Pantheon, Copenhagen 1968, pp. 63–78, 94–100, 133–142; Blake 1973, n. 4, pp. 42–48; William L. MacDonald, The Architecture of the Roman Empire, vol. 1: An Introductory Study, London 1965, 2nd ed. rev. New Haven 1982, pp. 94–118.

  7 However, in Chapter Five, Gene Waddell argues that once the relieving arches pass into the body of the fabric, they are composed in part of brick, part of concrete. In any case, the overall effect on the manpower figures is relatively small.

  8 Licht 1968, pp. 35–58; Louise Rice, “Urbani VIII e il dilemma del portico del Pantheon,” Bollettino d’arte 143, 2008, pp. 93–110.

  9 Licht 1968, pp. 48–56, Figs. 52–63, 72; Rice 2008b.

  10 According to Licht (1968, p. 44), several of the blocks of the pediment had been used before, and there are Severan brickstamps from the upper part of the intermediate block facade above the portico (Hetland 2007, n. 5, p. 101; for brickstamps: Corpus Inscriptionum Latinarum [CIL], XV 155.2 and 157.1).

  11 The exceptional bronze ceiling (or roof) of the caldarium of the Baths of Caracalla makes it clear that the large-scale constructional use of bronze was current in the Severan period; see Janet DeLaine, “The ‘cella solaris’ of the Baths of Caracalla in Rome: A Reappraisal,” Papers of the British School at Rome 62, 1987, pp. 147–156.

  12 For roof construction in general, see F. C. Giuliani, L’edilizia nell’antichità, Rome 1990, pp. 59–68. Details are taken from historical sources: the width of the truss elements are assumed to be equal (James Newlands, The Carpenter’s Assistant: The Complete Practical Course in Carpentry and Joinery, London 1990, p. 137), and other dimensions for the various timbers used in traditional systems (e.g., purlin, tie-beam, etc.) are from the tables in C. Paola Scavizzi, Edilizia nei secoli XVII e XVIII a Roma: ricerca per una storia delle tecniche, Rome 1983, pp. 38–42. The number of rafters and battens were determined by the potential size of the (assumed) marble roof tiles. The size of the marble tiles are based on those used on the Pantheon cupola (Lucos Cozza, “Le tegole di marmo del Pantheon,” Città e architettura nella Roma imperiale: atti del seminario del 27 ottobre 1981 nel 25˚ anniversario del Accademia di Danimarca, Odense 1983, pp. 109–118).

  13 Beltrami 1898, n. 6, esp. Figs. X–XV, XXII, XXV, XXXIV, and XXXV, summarized in Licht 1968, pp. 172–176; Paola Virgili and Paola Battistelli, “Indagini in piazza della Rotonda e sulla fronte del Pantheon,” Bullettino della Commissione Archeologica Comunale di Roma 100, 1999, pp. 377–394. See also Chapter Two in this volume.

  14 Lancaster 2005, n. 2, p. 59, and Fig. 1; DeLaine 1997, n. 3, p. 132, and Fig. 3; Sheila Gibson, Janet DeLaine, and Amanda Claridge, “The Triclinium of the Domus Flavia: A New Reconstruction,” Papers of the British School at Rome 62, 1994, pp. 80–86.

  15 See G.T. Schwarz, “Antike Vorschriften für Fundamente und ihre Anwendung auf Römische Bauten in der Schweig,” Provincialia Festschrift Rudolf Laur-Belart, ed. E. Schmid et. al., Basel 1968, pp. 448–453.

  16 Note that Licht 1968, p. 92, n. 5, has doubts about the depth of foundations. Even if the clay really does lie under the foundations, then we might expect that it had previously been consolidated by piling, a common Roman technique in water-logged conditions, especially in road construction.

  17 Licht 1968, passim, and especially Figs. 97–99, p. 105.

  18 Thanks are due to Nikolaos Theocharis and Michael Heinzelmann of the Pantheon project carried out at the Karman Center in Bern for providing figures for the volume of the dome at different levels, thus avoiding otherwise very difficult calculations.

  19 For the brickstamps from the Saepta, see Bloch 1937–1938, pp. 107–108; Hetland 2007, n. 5, p. 100.

  20 For the importance of such infrastructure in later periods, see Nicoletta Marconi, “The Baroque Roman Building Yard: Technology and Building Machines in the ‘Reverenda Fabbrica’ of St. Peter’s (16th–18th Centuries),” Proceedings of the First International Congress of Construction History 2, ed. Santiago Huerta, Madrid 2003, pp. 1357–1367.

  21 The most complete handbook is Giovanni Pegoretti, Manuale practico per l’estimazione dei lavori architettonici stradali, idraulici e di fortificazione per uso degli ingegneri ed architetti, 2 vols., Milan 1869.

  22 In London in 1749, ordinary brickwork was rated at 1,000 bricks/day, facework 500/day (B. Langley, The London Prices of Bricklayers’ Materials and Works, London 1749, pp. 87, 100–101). In London in 1865: 700–500 bricks/day (J. T. Hurst, A Handbook of Formulae, Tables, a
nd Memoranda for Architectural Surveyors and Others Engaged in Building, London 1865, pp. 214–216. In Italy in 1869: ordinary brickwork, av. 700 bricks/day (Pegoretti 1869, vol. 2, pp. 144–145). The figures have been adjusted for a common working day of 10 hours.

  23 For a discussion of principles and justification of choices made, see DeLaine 1997, n. 3, pp. 103–109.

  24 Final figures can thus only be considered as generally reliable to the first significant figure, i.e., the first digit plus the order of magnitude, with the second providing some guidance; thus, for example, a calculated total of 4,237.345 days of labor would be given as 4,240 days to three significant figures, but only the 4,000 would be considered really reliable within the specific assumptions made about working conditions, while the 240 would indicate only that the amount was likely to be closer to 4,000 than 5,000.

  25 Licht 1968, pp. 38–39, 62, 87, 157, Fig. 193; cf. Chapter Seven in this volume.

  26 See Lancaster 2005, pp. 51–53, on the setting and curing of pozzolanic mortars. Tests on a modern reproduction of Roman concrete using pozzolana from the Bay of Naples show the concrete still gaining strength after a year (E. Gotti, J. P. Oleson, L. Bottalico, C. Brandon, R. Cucitore, R. L. Holdfelder, “A Comparison of the Chemical and Engineering Characteristics of Ancient Roman Hydraulic Concrete with a Modern Reproduction of Vitruvian Hydraulic Concrete,” Archaeometry 50, no. 4, 2008, 576–590).

  27 See Chapter Seven in this volume.

  28 See Chapter Seven in this volume. While Mark Wilson Jones argues that the impetus for this was a crack in the drum of the rotunda that appeared when the drum was half built, it is also worth noting that the vault that supports the upper part of the grottoni must also have been integral to the Basilica of Neptune, which was less likely to have been able to resist any excess thrust from the Pantheon than vice versa. It is thus possible that the impetus to build the bridge was some structural problem with the Basilica, not with the Pantheon. Note that Licht 1968, p. 148, associates the second buttress behind the Basilica of Neptune apse with the Basilica, not the Pantheon drum. Unfortunately, not enough of the Basilica remains to test this hypothesis.

  29 See Chapter Seven in this volume, and cf. Paul Davies, David Hemsoll, and Mark Wilson Jones, “The Pantheon: Triumph of Rome or Triumph of Compromise?” Art History 10, 1987, pp. 133–153; Mark Wilson Jones, Principles of Roman Architecture, New Haven 2000, pp. 199–211.

  30 See Rita Volpe and F. M. Rossi, “Nuovi dati sull’esedra sud-ovest delle Terme di Traiano sul Colle Oppio: percorsi, iscrizioni dipinte e tempi di costruzione,” in S. Camporeale, H. Dessales, and A. Pizzo, eds., Arqueología de la Construcción, vol. 3: Los procesos constructivos en el mundo romano: la economía de las obras, Anejos de Archivo Español de Arqueología LXIV, Madrid-Merida, 2012, pp. 69–82.

  31 John R. Spencer, Filarete’s Treatise of Architecture, New Haven 1967, IV.23v; Volpe and Rossi 2012, pp. 69–82.

  32 This can be calculated as follows, using the lower zone of the rotunda as an example (figures from Table 6.1):Total mandays of bricklayer and assistant laying face, core, and arches/bonding courses = 684 + 40,300 + 240 = 41,224 mandays

  Since one-third of this is for the assistants, total mandays of bricklayer working at face = 41,224 x 0.667 = 27,482 mandays

  Since maximum number of bricklayers is 104, minimum number of days = 27,482 ÷ 104 = 264.

  33 Hetland 2007 and Chapter Three in this volume.

  34 Herbert Bloch, I bolli laterizi e la storia edilizia romana. Contributi all’archeologia e alla storia romana (1936–1938), Rome 1947, pp. 103–107.

  35 For two different examples, see Herbert Bloch, “The Serapeum of Ostia and the Brick Stamps of 123 AD,” American Journal of Archaeology 63, 1959, pp. 225–240; Janet DeLaine, “Building Activity in Ostia in the Second Century AD,” Acta Instituti Romani Finlandiae 26, 2002, pp. 41–102; pp. 93–99.

  36 See Chapter Seven in this volume.

  37 Pliny the Elder, Naturalis Historia, 36, 55, records an old prescription in Rome that forbade the use of lime that had been slaked for less than three months.

  38 There is evidence to suggest that the area in front of the Mausoleum of Augustus may have been used as a marble working yard for the Pantheon. See Lothar Haselberger, “Ein Giebelriss der Vorhalle des Pantheon. Die Werkrisse vor dem Augustusmausoleum,” Mitteilungen des Deutschen Archäologischen Instituts, Römische Abteilung 101, 1994, pp. 279–308; cf. Martin Maischberger, Marmor in Rom: Anlieferung, Lager- und Werkplätze in der Kaiserzeit, Wiesbaden 1997.

  39 See Chapter Seven in this volume.

  40 See Bloch 1937–1938, pp. 107, 115, and cf. Chapter Three in this volume.

  41 DeLaine 1997, n. 3, pp. 191–193, Tables 21–23. This is just for construction, and just for the central block. Even more men were required for the extensive substructures, as many as 9,000 if these were built in a single year.

  42 For the brickstamps of the Saepta dated to 123 and 127, see Bloch 1937–1938, pp. 110–111. For the Baths of Agrippa, see Giuseppina Ghini, “Thermae Agrippae,” in E. M. Steinby, ed., Lexicon Topographicum Urbis Romae, vols. 1–5, Rome 1995–1999; vol. 5, 1999, pp. 40–42. The Scriptores Historiae Augustae (Vita Hadr. xix.10) also lists the Basilica of Neptune, the Saepta, and the Baths of Agrippa alongside the Pantheon among the buildings Hadrian restored at Rome.

  43 Amanda Claridge, “Hadrian’s Lost Temple of Trajan,” Journal of Roman Archaeology 20, 2007, 54–94.

  44 See note 29.

  45 A. Cassatella, “Venus et Roma, Aedes, Templum,” in Steinby 1995–1999, vol. 5, 1999, pp. 121–123.

  Seven Building on Adversity: The Pantheon and Problems with Its Construction

  Mark Wilson Jones

  The fame of the Pantheon derives substantially from its wondrous engineering. The immense clear span went unchallenged for thirteen centuries until Brunelleschi raised the dome of Florence’s cathedral, and still the ancient feat is unrivaled as a work of unreinforced concrete. This prompts many questions for the casual visitor and the specialist alike. How was the building constructed? How long did it take to erect? What was the relationship between the various parts? In conjunction with the research of Janet DeLaine, Giangiacomo Martines, and Gene Waddell in this same volume, my aim is to advance these questions to the point of charting and explaining the sequence of building operations that is summarized graphically in Plate XIII.

  One way of framing the inquiry is to ponder why the Pantheon has survived intact despite the passage of almost nineteen centuries, bearing in mind that so many other Roman wide-span buildings have not. It is characteristic of this enigmatic monument that the answer is not entirely straightforward. The Pantheon owes its survival to its transformation into a church in the early seventh century, yet doubtless this initiative reflected admiration for the grandeur of the Rotunda in the first place. In any event, the acquired Christian status ensured some remedy for the various injuries suffered down the ages. Most notably, as a replacement for the earlier theft of its original gilded bronze tiles, the dome received a lead covering during the reign of Gregory III in the eighth century. This represented by far the most important single protective measure – who can guess how many other imperial interiors would have survived if they, too, had had their roofs maintained? The front end of the building had a more checkered fortune. Bell towers and the like were added and removed from time to time, while a convent, shops, stores, and hovels latched on to the structure like limpets; each intervention inevitably brought a degree of destruction, contributing to the dilapidation and partial collapse of the east end of the portico.

  It is perhaps surprising that more has not collapsed than just a portion of the portico. After all, the interior span comfortably exceeds any other ancient rival; the actual figure of 43.7 meters, measured from wall to wall, was determined by the axial diameter assigned to the ring of columns of 150 Roman feet (44.3 meters). The next largest surviving Roman domes spanned closer to 100 feet, this being the diameter of the misnam
ed Temple of Diana at Baiae.1 Other large domes may once have existed of which we have no trace, yet clearly the Pantheon was an exceptionally ambitious undertaking even by the standards of the high imperial period.

  The Pantheon’s survival depends most of all on the technical quality of Roman construction, which reached its apogee in the first half of the second century AD. This derived from a long tradition of intelligent experimentation with materials (primarily brick and concrete) and spatial-constructional units (arches, vaults, and the special kind of vaults we call domes).2 Illustrative of the attention to technique of the Pantheon’s builders is the grading by density of the aggregate in the concrete, with the heaviest at the bottom and the lightest at the top (see Fig. 1.12). In the upper parts of the dome pumice (or, rather, scoria) was used, a lightweight volcanic material from the region around Vesuvius, which was acquired only with difficulty after the eruption of AD 79 had covered the best deposits under inferior material.3 As Martines relates in Chapter Four, Roman builders also placed much faith in so-called relieving arches, and here too the Pantheon provides the most elaborate known array (Fig. 7.1, and see Fig. 1.13).