The Pantheon: From Antiquity to the Present

by Unknown

  XXII. Pantheon, east stair, sounding “S7” near the top of the rotunda. (Photo Mark Wilson Jones)

  XXIII. West stair, detail of sounding on level 2. This shows the “gut” of the construction at the junction between the rotunda and transitional block. Note the continuity of mortar and aggregate, as well as a whole bipedalis (indicated by arrow) that traverses the junction. (Photo Mark Wilson Jones)

  XXIV. Manfredo Manfredi, permanent tomb of Vittorio Emanuele II, lateral niche of the Pantheon, begun 1884. (Photo Robin B. Williams)

  These observations effectively eliminate all previous proposals that would claim that the main parts of the Pantheon were built completely separately. That the rotunda was never planned to stand on its own is further confirmed by the connections between the staircase and the chambers encased within the drum (Figs. 7.7, 7.8). These connections, being perfectly intact, were part of the original construction. This confirms what has become evident given the other considerations mentioned: the stairs were anticipated from the outset. And if the stairs were envisaged, so too must have been the transitional block as a whole.

  Inspection of the brickwork surfaces and of the courses of bipedales running around the stair offers further clarification of the relationship between parts of the fabric. The courses of bipedales are particularly instructive, for they traverse at intervals the entire thickness of construction, like layers in a layer cake (Fig. 7.7 and Plate XXIII). In the lower half of the staircase, the bipedales, save for a few exceptions, run at the same level around all four walls, which suggests that these were coeval. This coordination is less pronounced higher up, but one bipedalis course on the sixth turn of the stairs runs right around the staircase and all the way to the dome. That this occurs in spite of the separation between the rotunda and the transitional block points to the temporal proximity of the entire complex, suggesting that work on the latter only suffered a short-lived hiatus. Operations must have resumed on the upper half of the transitional block quite quickly, probably within a year or two.27

  The Connection between Transitional Block and Portico

  The excavations of the 1890s supervised by Luca Beltrami indicated that the foundations of the existing portico and those of the transitional block were made at the same time. This was later confirmed by A. M. Colini and Italo Gismondi in their study.28 They also reinforced Leclère’s observation of the continuity displayed by the entablature running longitudinally, noting that the blocks incorporating the capitals of the pilasters in the portico are embedded into the fabric of the transitional block too deeply to have been inserted in a separate epoch.29 (Part of the rough marble of a capital block can be seen where it disappears into the masonry in Figure 7.10, right, though it is impossible to gauge the full extent of its penetration; this is indeed considerable, as I have been able to observe from close quarters when there was scaffolding in place.) Colini and Gismondi also noted that the brickwork facing the transitional block has a single inclined line of bipedales tracking just above the portico roof, but not at exactly the same angle. This suggests perhaps that the roof was contemplated when this part of the transitional block was built, though some adjustments came to be made in the course of execution.30

  7.10. Pantheon, vestibule, and transitional block at the junction with the portico. Note the unusual grouping of pilasters, and in particular the conjunction of one that forms part of the transitional block with the three-pilaster-faced anta. All four of the antae in the portico have sides toward the great niches that are wider than the other faces. This creates a “leftover” rough portion on each of the capital blocks, since the capitals proper are maintained the same width throughout. The result may be seen on the far right. This and other capital blocks are embedded into the fabric of the transitional block. (Photo Mark Wilson Jones)

  The portico and transitional block were, then, planned together and their joint foundations implemented together. The portico cannot have been added in a completely separate campaign. This does not mean, however, that both marched exactly in step. In fact, the raising of columnar structures was normally carried out after completion of any associated masonry structure (see Chapter Six), while there were also reasons that led to a greater delay than normal in this particular instance, as we shall see.

  To summarize our examination so far, the fabric of the Pantheon reveals the following:

  All three main parts of the Pantheon, rotunda, transitional block, and portico, belong to a unitary initial conception.

  At the south end, the grottoni were not part of the original project; they were added after the commencement of the rotunda, but were built so quickly as to catch up and become united with it before the dome was far advanced.

  At the north end, the rotunda and transitional block are bonded at the bottom, but about halfway up the elevation the procedure changed. Work was next carried forward on the rotunda alone, with the rest of the transitional block following on soon afterwards.

  A portico was planned as part of the project from the outset, but it was the last major part of the edifice to be implemented.

  The curious phasing of the grottoni can be explained as a response to concerns about the stability of the rotunda, while building the portico last made practical sense. But how can we explain the interruption of work on the transitional block?

  Can there be an explanation of a structural kind, for example differential settlement between the rotunda and the transitional block? However, there are no signs of such. Those lesions that are present in the staircases respond to the general pattern of cracks affecting the rotunda as a whole, and they tend to peter out before ground level. There is no cracking visible in the sounding in the west stair where the rotunda and the transitional block intersect (Plate XXIII). Nor are there any significant lesions in the side walls of the staircase (those that run north–south). What explains, then, the hiatus in building the latter? This is an issue, I contend, that cannot be resolved by focusing on construction alone. It is now time to turn to issues of design that might bear on the same puzzle.

  The Front of the Pantheon and the “Compromise Hypothesis”

  While the structure of the Pantheon solicits both wonder and alarm, its design has historically provoked just as varied responses. Alternating between praise and criticism, the paradoxical fortuna of the monument has been charted lucidly by Tilmann Buddensieg,31 while surfacing in the Introduction to this book, and in some chapters in the second half. Criticism of the interior was mainly directed at the attic level, and especially the pilasters for being too small and for not aligning with either the main order below or the coffering above. This can be understood as a misplaced faith in academicism, which tended to dominate from the time of the Renaissance, and in particular the “law” of vertically aligning like with like. Instead, we may delight in a coherent scheme that spurns a predictable radial solution for the sake of a genuinely dynamic experience. The “push and pull” effect of the openings and exedras on the eight main axes is accentuated by compositional alignments avoided elsewhere.32 (The proof that all of this was deliberate lies in the way the floor pattern meets the rotunda, being similarly synchronized exclusively on the eight main axes.) Because it is not so obviously tied visually to the drum, the dome appears to hover with an indefinable magical quality.33

  Criticism of the exterior has concerned the difficult marriage of the rotunda, transitional, block and portico, as exemplified by the abrupt termination of the entablature where the circular and orthogonal geometries meet (Figs. 7.9, and 7.11, and see Fig. 1.9). Along with various “solecisms” – offenses to the classical “grammar” of the orders – this lack of unity used to be seen as the legacy of separate phases. Giorgio Vasari related how many artists of his time, “Michelangelo among them, are of the opinion that the Rotunda was built by three architects, the first carrying it up to the cornice above the columns, the second doing from the cornice upwards.... [T]he third is believed to have done the beautiful portico.”34 As late as the 1930s, Giuseppe
Cozzo, a specialist of Roman construction who should have known better, continued to maintain that the rotunda was built first (in the time of Agrippa), and the rest later (in the reign of the Severan emperors).35 This was an attempt to reconcile the main Agrippa inscription emblazoned on the frieze of the portico with the secondary longer inscription in smaller letters on the architrave.36

  7.11. Junction of the rotunda, transitional block, and portico on the west side. (Photo Mark Wilson Jones)

  But the enigma of the Pantheon is not to be solved in this way. Following the work of Georges Chedanne, Luca Beltrami, and Heinrich Dressel in the 1890s, scholars had to accept the implications of brickstamp studies (see Chapter Three). Leaving aside for a moment the precise dates implied, these showed that save for later repairs and alterations, the whole edifice was erected more or less in one go. What explains, then, the character of the design? The inept collision of rotunda, transitional block, and portico continued to elude a positive interpretation, representing something of an embarrassment to be sidestepped as deftly as possible by anyone writing about the Pantheon in the course of the twentieth century.37

  Paul Davies, David Hemsoll, and I attempted an explanation of a quite different kind in 1987, arguing that the front of the Pantheon is not what was originally intended, but rather the outcome of compromises induced by circumstances beyond the architect’s control. The “compromise hypothesis” proposes that the portico was originally planned to have a roof at the level of the existing upper pediment, a roof supported on columns incorporating monolithic shafts of Egyptian granite 50 feet in length and 100 tons in weight (Fig. 7.12, Plate XVII).38 For some reason unknown – perhaps because a consignment of the intended shafts had sunk at sea en route between Alexandria and Rome – only after work had started on site was the decision made to employ 40-foot shafts instead.39 It is important to note that Roman monolithic column shafts tended to be standardized in multiples of 4- and/or 5-foot lengths, and that they were typically worked up to near-finished form in major quarries across the Mediterranean world. Large examples can still be seen where they were abandoned in several quarries, including those of Mons Claudianus, the source of the shafts for the front file at the Pantheon. In the context of grand imperial monuments, 40 footers represented the next major step down from 50 feet, and it was this smaller size that was actually used. Forty footers were also much more common (and they weighed only half as much, though this was probably not the key factor).40

  7.12. Pantheon plans and elevations, intended and as executed. (Wilson Jones 2000, Fig. 10.12)

  Although it should perhaps not be admitted in the politely serious domain of scholarly discourse, our article of 1987 was conceived by chance in a London pub after a day studying other things in the Warburg Institute, while sketching from memory. But what started as a bit of speculative amusement came to take on substance upon further research. Calculation showed that 50-foot shafts were perfectly commensurate with an order rising to the cornice running around the rotunda and the start of the upper pediment. Meanwhile, scrutiny brought into focus the solecisms that had worried so many past commentators, while revealing some previously unnoticed ones. In effect, there is quite a tally of features that are sufficiently unusual or perverse as to raise the question of whether they were really intended in the first instance. Here follows the list of points as they stood in the year 2000:41

  i. The transitional block is faced with an accessory pediment that is partially cut off by the main roof (Fig. 7.9). No known earlier building has a comparable arrangement save for the Propylaea of the Athenian Acropolis.

  ii. The entablature of the portico terminates abruptly at the rotunda, failing to align with the moldings of the latter (Figs. 7.9, 7.11).

  iii. The portico pediment is exceptionally tall in relation to the height of the order (Fig. 7.12, and see Plate I), to judge by the proportions of other Roman buildings of similar size, such as Augustus’s temple of Mars Ultor.

  iv. The cornice brackets or modillions of the portico pediment are smaller and are spaced at more frequent intervals than those of the upper pediment, despite the fact that both pediments are the same size (Fig. 7.9).

  v. The gaps between the columns, or intercolumnations, are unusually large relative to the column diameter when compared with most other monumental imperial colonnades (although widely spaced rhythms did also exist).

  vi. The antae in the portico are oddly unbalanced. The sides facing the great niches are wider than the rest, an arrangement that gave rise to an unsatisfactory resolution of the capitals overhead (Figs. 7.10, right; 7.13, partial plan)

  vii. The central aisle of the portico becomes narrower where it enters the transitional block; here is a peculiar grouping of pilasters, as if the ones nearer to the entrance door were added after the others were already in place (Figs. 7.10, 7.14).

  viii. Where the portico meets the transitional block the entablature steps out by a small amount, one neither so small as to be insignificant nor so big as to constitute a positive feature (Fig. 7.11).

  ix. The transitional block is only bonded with the rotunda in the lower levels of the building. In the upper parts, it merely runs up against the rotunda, as has just been confirmed in the preceding discussion (see Fig. 1.9).

  All such solecisms and curiosities would simply not have existed in the hypothetical original project (Plate XVII). Scholarly responses to the compromise hypothesis have been favorable, though of course not everyone is convinced.42 Lothar Haselberger, the author of important publications on the building, hastaken issue with such an approach, highlighting the danger of presuming that we can know what ancient architects intended, along with specific objections to some of the points just outlined.43 For him, the juxtaposition of exacting details with various “misfits” could reflect an approach to making buildings that we have yet to fully appreciate, in this as in other imperial monuments.44 His is wise council, but yet the juxtapositions he notes (precise-imprecise, regular-irregular, and so on) seem to me not so much to detract as perhaps to add to the argument, for they remain easier to understand in a situation where a design had to be compromised, delayed, and possibly rushed as a consequence. In any event, not one of the previous points has been definitely disproved. And no one has yet been able to show how and why we should positively celebrate the front of the Pantheon in the same way as we certainly can the interior.

  7.13. The portico as built (top) and as intended (bottom). Transverse section through the portico, with the transitional block and rotunda seen in elevation, 1: 400, with part-section top right and part-plans in the middle. (Drawing Mark Wilson Jones)

  7.14. The vestibule and door, seen on axis with view through to the rotunda beyond. Originally a bronze, suspended, vaulted ceiling would have abutted the reveal of the masonry barrel vault over the vestibule. (Photo Maxim Atayants)

  Other responses to the compromise hypothesis take the form of qualified support, such as that published by Rabun Taylor in his book Roman Builders; he runs with the idea of a compromised Pantheon portico, but adapts it in favor of hypothetical columns that were taller still.45 Yet Taylor’s 55-foot shaft size is not able to appeal to evidence of the same kind that favors 50 footers. One such is a letter on papyrus from an Egyptian contractor dating to Hadrian’s reign. It calls urgently for fodder for animals involved in transporting overland a single 50-foot granite shaft from the quarries at Mons Claudianus to the Nile, and thence to Alexandria, from where it would in all certainty have been bound for Rome.46 Another coincidence concerns the working drawing template of the Pantheon pediment inscribed on the pavement in front of the Mausoleum of Augustus (see the Introduction). The pediment crosses over the plan of a capital that is too big for the actual building, but which freakily happens to be precisely the size that the hypothetical project predicts.47 A much damaged 50-foot granite shaft lies under the sea off the ancient port of Alexandria, while the possibility of 50 footers arriving in Rome is underlined by the recent discovery of stumps in the
imperial fora.48 The find-spot points to their use in the focal cult building of the vast precinct known as the Temple of Peace, begun in the early 70s AD. This adds to the very rare instances of 50-foot monolithic shafts already known in the city: the broken one lying by Trajan’s Column and companions under the nearby palazzo Valentini, which belonged to the Temple of Trajan, as well as the shaft of the Antonine column, which was also of Egyptian granite and extracted in the time of Trajan. Trajan’s Baths is another candidate.49 The quarrying, transportation to Rome, and erection of such 100-ton monster stones was thus a feasible imperial ambition, albeit one so audacious that it stretched the Roman building machine to the limit.50

  It is possible to marshal further fresh evidence in favor of the compromise hypothesis. My inspection of the staircases has established once and for all that the rotunda and transitional block are united at low level, and so part of a unified project. The compromise hypothesis offers an explanation for the interruption of work on the transitional block; furthermore, it fits neatly with a hiatus of relatively short duration during which the design was argued over and revised.