The restoration work
It is an honour for our group to talk about Trajan’s Column die quarto ante Idus Maias, in Vindobona.
We spent eight years on the restoration of this monument, from 1981 to 1988, and we are delighted to show you the drawings we made at that time.1 In those years, the Superintendent of Rome’s Archaeo-logical Heritage was Professor Adriano La Regina. A brief word about the reasons for that restoration before we start.
At the end of the seventies, all the ancient monuments in the historic centre of Rome, those in marble, were covered with a blanket of centuries old dust, smog from car fumes, soot from heating systems, which then were coal fired. The Soprintendenza Archeologica di Roma began to take a close look at the situation, carrying out detailed inspections and chemical analyses of the deposits: the mar-ble surfaces were crumbling as a result of sulphation, the calcium carbonate being transformed into calcium sulphate, i.e. gypsum, which melts in the rain. Our Parliament immediately voted a law “Ur-gent Measures for the Protection of the Archaeological Heritage of Rome,” on March 23, 1981. The Ministry decided to protect all the marble monuments of ancient Rome from the rain and built scaf-folds around them, so that scientists could assess the problems and restorers could conveniently get to work, as if within a workshop. In a short time the landscape of the historical centre changed: all mar-ble monuments were surrounded by scaffolding, with ramps and platforms; it became a huge tempo-rary outdoor archaeological museum. The scaffolds were periodically open to the public and archae-ologists and restorers gave guided tours. A symbol of those surveys, conducted at close range on so many monuments and at the same time, was Amanda Claridge’s discovery of small circles used to trace and sculpt the flutes on the shafts of the columns.2
At the end of the restoration, in 1988, the first to benefit was the general public: the old town was freed from automobile traffic, and heating systems used natural gas. The monuments could once again be admired and they are still there for everyone to see after more than twenty years.
For the restoration a light wash system was developed using ordinary water spray; sulphated parts were consolidated with ethyl silicate, both before and after being washed; the cracks were plastered with lime putty mortar to prevent rain getting into the marble, taking the same care as a dentist with a tooth.3 The lime was seasoned for three years, as prescribed by Pliny, in the Palatine lime pit, under the Horti Farnesiorum.4 The patina covering the ancient bas-reliefs was left in place because it is in itself a form of protection from the weather. The patina poses an immediate problem: is the beautiful gold patina natural or artificial? How long have the patinas been there? Since then, they have been observed throughout Europe, on cathedrals, and scientists have established that they are all based on calcium oxalate.5 Their origin remains a mystery. In those eight years of restoration, more gaps ap-peared in our knowledge than were filled. This we realised almost immediately and it determined a basic rule for all restoration sites: prudence.
* This paper has been translated by Fred Moffa, the British Institute of Rome, whom we would especially like to thank.
Roberta Zaccara, to whom I am grateful, edited the illustrations and in particular the composition of figs. 1 and 4. This study is dedicated to the memory of the architect Maurizio Sacripanti.
1 Martines (2001).
2 Claridge (1982). These small rings were observed on Trajan’s Column: they were cut into the necking at the top of the striae, fillets that separate the flutings on the capital: Martines (1992), particularly fig. 11.
3 Conti (1999); Conti, Martines (1996a).
4 Conti, Martines (1996b), particularly 201, fig. 1.
5 Alessandrini (1989).
Giangiacomo Martines 42!
In 1988, the end of the restoration was celebrated by three different publications: by Frank Lepper and Sheppard Frere;6 by Salvatore Settis, Adriano La Regina, Giovanni Agosti and Vincenzo Farinella;7 and by Philippe Morel.8
The survey
For the restoration work, the first thing we needed was a large format drawing of the entire carved frieze, to record all the observations and then prepare for work. We had the engravings of Pietro Santi Bartoli9 and Piranesi,10 but they did not reveal all the complexities of the bas-reliefs. It was then de-cided to make a full-scale tracing of the bas-relief, as children do at primary school, but without touch-ing the marble surface. For the survey an interdisciplinary team was formed: architects for the repre-sentations and the problems of descriptive geometry; archaeologists for the iconography and construc-tion techniques; chemists, physicists, and restorers; at that time there was no computerizaconstruc-tion.
Therefore, the first problem was to choose the datum points on the monument, i.e. the horizontal planes and vertical lines to fix the correspondence between the shaft of the column and the frieze, which winds round it in a spiral. It was the column itself that revealed its reference system: the hori-zontal planes of the drums and vertical axes of the windows. From the capital, down the middle of the four sides, plumblines were dropped, as if they were the perpendicula of a colossal groma used by Roman surveyors (Pl. 1, Fig. 1).11 All the measurements were taken in reference to the plumb lines, which remained in place until the scaffolding was dismantled.
The carved frieze was projected flat (Pl. 2, Fig. 2)12. The shaft is cylindrical at the bottom, up to a third of its height, and above it is conical, as a result of tapering, entasis.13 The entire frieze was pro-jected in accordance with Ptolemy’s second projection of the world,14 constructed with curved meridi-ans and parallels; in the case of Trajan’s Column, the parallels are the joins at the tops of the drums, while the meridians are the perpendicula of the groma along the windows. We have to imagine a pro-jection surface tangent to the shaft of the column, i.e. a large sheet of cellophane, on which the carved frieze was traced. In this way a flat drawing could be made without any distortions. The full-scale drawings were then reduced to a scale of 1 to 5; the drawings of the entire frieze are contained in 68 panels that can be joined into a whole 238.4 cm wide and 527.9 cm high.15
The Column’s height: centum pedes?
Despite the many precise measurements (Pl. 3, Fig. 3),16 there still remains a problem: the centenaria height of the column (base + shaft + capital) (Pl. 4, Fig. 4).17 Also doubtful is the length of the Roman foot used to build the column.18 In the years 1981–1988, Heinrich Bauer measured all the monuments being restored in search of the foot, concluding that the foot in use in Rome was the hundredth part of
6 Lepper, Frere (1988).
7 Settis (1988).
8 Morel (1988).
9 Bartoli, Bellori (1672).
10 Piranesi (1774).
11 In Fig. 1, the Roman soldier with the groma is taken from: Frigerio (1932–1933), particularly 96, pl. 2; the engraving of Trajan’s Column is taken from: Piranesi (1748–1778) 2, fol. 30.
12 From Martines (2001) pl. 1.
13 According to Wilson Jones (2000) 130 and fig. 6.32, the entasis of Trajan’s Column is formed “… with an ample arc sandwiched between two straight sections”.
14 Harley, Woodward (1987) 186–188. For the plan of the bas-relief, the system of projection was arranged by Marco Pel-letti, of Modus Società Cooperativa, Rome.
15 Martines (2001) pl. 2–69.
16 Martines (2001) pl. 78.
17 Martines (2001) pl. 87. The measurements on the right of the drawing were taken from: Martines (2000), particularly 84–86, pl. 9. About the order: Florescu (1969) 38–56, especially fig. 15.
18 Martines (1999b).
Description of the Structure 43!
the base of the Pyramid of Caius Cestius, 29.47 cm, which was valid also for Trajan’s Column.19 The problem of the centenaria height concerns the plinth at the base (Pl. 5, Fig. 5); in fact, to quote Bauer:
“As for the height of Trajan’s Column, including plinth and capital, we should first of all say that the
‘plinth’ does not have the normal shape of a parallelepiped but is in fact double the cavetto moulding of the cornice below and rises in a parabolic curve”.20 Instead, in the relief made by Marco Pelletti (Pl.
5, Fig. 6),21 67.7 cm of the upper cavetto is perfectly vertical. From this point the column is exactly 29.6 m high.
This hypothetical horizontal limit, even if made on a papyrus drawing, was cancelled. Apol-lodorus combined two elements of the order, the plinth at the base of the column and the eaves at the top of the pedestal. In this way, Apollodorus achieved figurative continuity between the pedestal and column.
The drums of the shaft
The entire structure is made up of 29 blocks: 8 huge parallelepipeds form the podium or pedestal; 19 drums make up the shaft with the torus and the capital, which is round underneath and square above;
another 2 drums form the pedestal which supported the statue of the emperor (Pl. 6, Fig. 7).22 The blocks of the podium are arranged on four levels, in pairs perpendicular to each other. The interior of the column is partially hollow and has a staircase going through it, which leads to the terrace on the capital. The emperor’s burial chamber is at the level of the Forum. In the podium, the stairway climbs up with 4 flights of stairs. Above the podium, the stairway continues in the form of a winding staircase inside the shaft, describing 11 coils + 2 steps.
Each complete coil of the winding staircase has exactly 14 steps (Pl. 7, Fig. 8.1).23 The ceiling is a perfect helicoidal area. The 14-part cyclotomy is rare in architecture because the heptagon is a polygon that cannot be constructed with ruler and compass.24 Each coil of the staircase is lit by 4 apertures arranged in cross, alternately on the axis of the Forum and the axis of the Libraries. The apertures on the axis of the Forum correspond to the edges of the risers, while the apertures on the Library axis correspond to the centerlines of the treads: this difference can help a person climbing up see where they are going and count the coils of the stairway.25
Therefore the shaft is made up of 19 monolithic drums,26 the height of each varies from 148.2 to 154.7 cm: evidently, this difference is due to the fact that each drum needed to be levelled, after a drum had been laid on another. What remains constant, though, is the division of the height of the drums into 8 risers of the spiral stairs (Pl. 7, Fig. 8.2). They are about 19 cm high, 1 bes, and are much easier to climb than the steps of the Colosseum, 1 pes, so you can reach the top without having to catch your breath and they are easy to come down.
The 8 risers have 7 treads, which together cover 180° (Pl. 7, Fig. 8.3). Thus in each drum, 8 treads make exactly a straight angle + 1 tread, i.e. ! + ! / 7:27 using this rule the helicoid joints never occur on the same vertical line, but progressively rotate.
19 Bauer (1983), particularly 136, note 33. Bauer, who died prematurely, rests at the foot of the Cestian Pyramid, in the historic cemetery. James Packer, too, established a similar length for the Roman foot, 29.38–29.40 cm, for Trajan’s Forum:
Packer (1997) I 471.
20 Bauer (1983) loc. cit., lit.: “Per quanto riguarda l’altezza della Colonna Traiana, compreso plinto e capitello, è da dire prima che il suo ‘plinto’ non ha la forma normale di un parallelepipedo ma è in realtà un raddoppio del guscio della cornice sottostante e sale in curva parabolica.”
21 Martines (2001) pl. 89 and 90.
22 Martines (2001) pl. 86.
23 Martines (1983).
24 Martines (1989), particularly 5–7.
25 Martines (2000) 24. For the geometry of the helix, in the 1st century CE: Hero of Alexandria, Definitiones 7, see Heiberg (1912); Giardina (2003) 178–179, 278–280.
26 Mark Wilson Jones hypothesised an original project for a shaft divided into 20 drums: (2000) 169–171, expecially fig.
8.15; Wilson Jones (1993).
27 Martines (1983).
Giangiacomo Martines 44!
The drums were originally joined by metal pins sealed with molten lead, without any mortar.
There are 4 pins for each join, placed at 45° to the axes of the windows (Pl. 7, Fig. 9).28 In the Middle Ages many pins were stolen to be melted down and made into weapons, pots and sickles; only two are left on the whole shaft.29 From the holes left by the thieves we can determine the shape of the pins and the mounting system: they were square, with 45–50 mm sides, 165 mm high, and certainly made of bronze; they were driven into the holes in the upper block, fitting into specially made wider holes in the lower block; after a drum had been laid on another, the empty space was sealed from the outside with molten lead, poured through raceways formed on top of the lower drum. So the ends of the lead seals remained in sight, forming grey half circles, with a diameter of 20 mm or less, corresponding to the section of the raceways on the horizontal line of the join (Pl. 8, Fig. 10). Where the drums joined, three pins were sealed from the inside and a fourth from the outside, because the solid marble helix made it impossible to seal the pins from the inside.
Each drum is formed by three distinct geometric bodies (Pl. 7, Fig. 8.2): a solid inner cylinder, an outer cylinder, and the part of the stairs between the two cylinders; these three bodies form a whole, which is carved out of a single block of stone. In this way, each drum is about 1/3 lighter than it would be if it were solid. For example, the third drum would weigh 43.7 tons if it were solid; instead, thanks to the hollow of the stairway and the apertures it weighs 29.9 tons.30 It is likely that the stairway was excavated at the quarry, or at least started there, to make it easier to transport the drums; the excava-tion was certainly finished at the building site, before being erected.
The monument is built e marmore Lunensi: blocks and drums were extracted from the Fantiscritti quarry, situated at an altitude of 630 metres above sea level.31 The entire structure (Pl. 6, Fig. 7) weighs 1,036 tons; the heaviest block forming the pedestal weighs 72.33 tons; the weight of the drums varies according to the height at which they were placed, from 29.85 to 22.30 tons; the torus weighs 50.37 tons and the capital 44.66 tons.32 These are considerable and exceptional weights even in the construction of public monuments; in the Colosseum and the Arch of Septimius Severus, built before and after Trajan’s Column, respectively, the heaviest block weighs 32 tons33 and this would seem to be the limit of the great Roman cranes like the wheel of Haterii.34
Another unresolved question is how the blocks were shipped by sea35 to the Tiber, transported to Rome to the building yard in Trajan’s Forum and, above all, how they were erected. As regards the latter, there are two hypotheses: first, the drums were either lifted by cranes and ropes;36 second, the drums were pulled up a chute or sloping plane.37 The three main problems in the lifting of weights by crane and rope are: the buckling force on the wooden masts of a hypothetical giant crane; the rolling friction of the ropes on pulleys; the tensile stress of the ropes themselves. According to Pliny the El-der, strong ropes were made of spartum,38 esparto grass, which is still used in mussel farming.
In conclusion, the shaft is lighter than an equivalent solid column by 1/3, and is more rigid than an equivalent hollow cylinder of marble. The helix gives the structure special strength, lightness, stiff-ness, even in earthquakes. These characteristics reflect the performance of an exceptional structure.
28 Piranesi (1774) pl. 8.
29 Martines (2000) 83, pl. 7.
30 In the third drum, the outer cylinder weighs 23.15 tons, the inner cylinder 3.4 and the stairs 3.35. The thickness of the stairs’ marble helix is constant, about 43 cm, just under a sesquipes: this is a relatively small thickness compared to the mass of the two cylinders. In the Column of Marcus Aurelius, the thickness of the stair helicoid is greater, 62 cm, more than 2 pedes: Martines (2013a) pl. 23–26; Martines (2000) 23.
31 Martines (2000) 19, notes 2–4 with bibliography.
32 Martines (2000) 75–76, pl. 1.
33 Bruno et al. (1999), particularly 160, pl. 1. Bruno, Bianchi (2006), particularly 310, pl. 1.
34 Martines (1998–1999).
35 Wirsching (2006); Wirsching (2007).
36 Lancaster (1999). In his studio in Pietrasanta, the sculptor Claudio Capotondi built a model of the drums of Trajan’s Column and a very convincing crane, which I saw with Prof. Giovanni Di Pasquale of the “Istituto e Museo di Storia della Scienza di Firenze”, in the Spring of 2010.
37 Martines (2000) 30–36. About the sloping plane: Di Pasquale (2012).
38 Coarelli (2008) 41. Plin. nat. 19.29–31.
Description of the Structure 45!
The winding stairway excavated in the cylinder of the marble shaft is an invention of this highly origi-nal structure.39
Apollodorus’ ability to conceive empty areas carved out of the drum can be credited to the experi-ences and traditions of his native land, the Kingdom of Nabataens:40 Petra. In Trajan’s Column, the width of the stairway is the same as a caesura, namely a trench in a stone quarry:41 a quarryman would open up a path along the slope of a mountain,above the blocks to be quarried. When the path was deep, the quarryman cut some steps. When the caesura, which literally means ‘cut’, was of the desired depth, the blocks were detached at the bottom with wet wooden wedges and then made to slide down the slope. In Trajan’s Column, the caesura is not straight as at Luni, but circular as in the quarries of Cusa in Sicily, where the drums of the temples of Selinunte come from.
In Trajan’s Column, the width of the stairway is just 75 cm and the average height 225.5 cm. The space is minimal but the climb up is easy, without any feeling of claustrophobia. These are same measurements used by Le Corbusier eighteen centuries later in Modulor.42
Trajans’ Column and !"#$"%&'($&): common concepts
There are concepts which are common to Trajan’s Column and the "#$%#&'()%'*, Siege-matters, the book by Apollodorus of Damascus.43 The most evident characteristics of his treatise are: the lightness of his machines, the ease with which large structures are constructed with small pieces, the fact that they can be dismounted after use and transported elsewhere, the simplicity of the material and work-force, the option of mass producing different pieces.44 All innovative characteristics if compared to siege works before Apollodorus: consider the wooden towers and earthworks for just one siege, such as Masada in 72 CE.45 In Trajan’s Column, each drum is like a piece of machinery, designed to be mass produced; the drums are relatively small and light compared to the gigantic size of the column.
The capacity to conceive minimal spaces, such as the stairway, can also be found in the Siege-matters: to open a breach in the enemy walls, two soldiers come up to the wall protected by a small tortoise formation and quickly start digging into the masonry with picks making enough room for one of them (Pl. 8, Fig. 11).46 Then both get in, but shoulder to shoulder, and continue to widen the gap, protected by the very wall they wish to demolish. So they prop up the hollowed out part with wooden logs which they will then set alight: +, -'*.)/ [0123'/] .'*4#5.% 67# 8!9.)&:µµ;,#%,47 “two men dig in each [alcove], back to back.”48
In Siege-matters, Apollodorus shows particular interest in the subject of centre of gravity of com-posite bodies, formed, that is, of similar material that are joined together. It is the problem of how to
In Siege-matters, Apollodorus shows particular interest in the subject of centre of gravity of com-posite bodies, formed, that is, of similar material that are joined together. It is the problem of how to