Construction And Restorations Between The 16th And 18th Centuries

2.1 The building site and the pre-existing structures

The study of events of the construction of the Gesu Nuovo church provides significant grounds for reflexion referred to multiple topics which are related to the construction and to the transformation of architecture since the 16th century. The analysis of historical sources suggests an articulated combination of interpretations of damage and, consequently, of methods of consolidation proposed during past centuries. At the same time, the examination of the planning choices which have been adopted in the substitution of parts -the dome in the crossing, particularly - highlights how the integration of lacking parts has been developed during each historical phase with a sincere expression of the contemporary "state of technique" and the culture of planning.

Since its establishment, the church of the seat of the Society of Jesus in the capital of the Spanish vicereign was planned in correspondence with the pre-existing architecture of the 15 th century palace of the prince of Sanseverino (De Frede 2000).

External facades were re-used in Giuseppe Vale-riano's project along three sides of the building for economic reasons and, moreover, for the recognition of its urban significance and role. The vertical perimetric structures of the palace were preserved and underfoundated (Pirri 1970, p. 116, p. 121, note 58) while the excavation of the four crossing pillars started in 1584, probably with the center of the crossing planned in correspondence to the palace courtyard (Schinosi 1706-1711, lib. V cap. VI, p. 464).

The reconstruction of the building phases is facilitated by information given by the Jesuit chronicler Giovan Francesco Araldo at the end of the 16th century (Divenuto 1998), together with historical data provided by documentary sources preserved in the Jesuit archive in Rome (Pirri 1970; Bösel 1985, vol. I, pp. 416-419). Through Araldo's narration it is possible to understand that the foundations of the four pillars were realised between November 1584 and March 1585, reaching the "monte, et ferma pietra", that is the tuff in the subsoil (Divenuto 1998, p. 238). Reading the Jesuit chronicler, we learn that the four pillars on which the dome had to be placed were built in only three months, from March to June 1585 (Divenuto 1998, p. 240 and p. 243), covering their tuff basements with piperno blocks. An interruption of approximately ten years in the building of the church followed the establishment of the pillars so that the construction was started again only in 1594 with work in the tribune and in its side chapels (Divenuto 1998, p. 372); construction times slowed down again in 1596 because a serious blaze burned in the church and because of the death of Valeriano in July. The construction of the crossing was started again only when the tribune was completed. The erection of the four arches discharging on the pillars - built about ten years before - and, finally, of the bottom ledge of the tambour concluded this building phase.

The church of Gesu Nuovo was inaugurated in October 1601 (Errichetti 1963, p. 183, note 2) without its central dome: about thirty years passed from the inauguration to the beginning of the construction of the Jesuit dome in 1629 (Errichetti 1963, p. 177).

2.2 The domes of the Gesu Nuovo church in the seventeenth century

Although it is scarce, useful information about the construction of the dome can be deduced from the seventeenth century cartography and, moreover, from the description of the structure and of its dimensions given by the Neapolitain guide Carlo Celano in 1692. The first dome of the Gesu Nuovo church had a tambour that was marked externally with buttresses with volutes (Figs 1 and 2). Two calottoes weighed on the tambour and they were separated by an interspace about seven metres high in correspondence with their keystone; in addition, a staircase leading to the lantern on top was constructed between the two vaults (Celano 1692, p. 44). The lantern, consisting of a cylinder of masonry surrounded by eight grey tuff columns,

Figure 1. Naples, the Gesü Nuovo church in the map of B. Stopendael (1653).
Figure 2. Naples, plan of Gesü Nuovo church and Professed House (17th century). The drawing shows the double calot-toes structure of the first dome of the church (Bösel 1985, tav. 271).

balustrades and vessels, produced a significant weight on the lower calottoes; as we learn from Celano, the lantern was the first element to crack shortly after its completion so that it required the replacement of a stone column with a brick one.

According to the above mentioned seventeenth century author, this intervention caused a "weak point" which was at the origin of the collapse of the Jesuit double dome, which occurred during the earthquake of 1688. Therefore, such a hypothesis, empirically tending to highlight the role played by the lantern in the collapse of the dome, had already been advanced in an "official report of damages" produced approximately one month after the earthquake; in fact, this document stressed that "the dome fell beginning to crumble from the lantern", striking in its collapse the lateral chapels of the transept (Cantabene 2004, p. 58).Through reference to the documentary sources, it is possible to suppose that the seismic tremors caused the loss ofthe two vaults and that of the lantern, while they spared the seventeenth century tambour which remained largely in place. This fact is confirmed by the description of the dynamics of the collapse provided by the Neapolitan architect Giuseppe Lucchese in 1708; this technician, engaged in the analysis of crackings of the double dome of the Treasury of St.Gennaro Chapel in the cathedral of Naples in the same year (Russo 2007), refused any hypothesis of a fall "on perpendicolo" of the Gesu Nuovo dome as had been advanced by contemporary "mathematicians"; on the contrary, he emphasised the rotation suffered by the vaulted parts and by the lantern towards the west transept side. As the report of Lucchese makes clear, the four arches, the pendentives and the tambour remained "firm and intact" (ATSG, A/22, foll. 66v-67); a circumstance that would not have arisen, according to Lucchese, in case of a collapse only in a vertical direction.

The Jesuits attended to the repair of the tambour, to the construction of the transept left vault again and to closing the crackings with lime and bricks in only six months (Errichetti 1963, p. 177). Thereafter, the collapsed parts were rebuilt following the plan of the Neapolitan architect Arcangelo Guglielmelli between 1692 and 1693 (Amirante 1990, p. 247 and p. 334). As a drawing of 1769 clarifies (Sasso 1856, tav. 13; Errichetti 1963, p. 178) (Fig. 3), a single vault concluded by a smaller lantern was built in order to replace the complex double dome of the beginning of the century (Fig. 4); its weight loaded, of course, on the pillars and arches dating, as said before, back to the end of the sixteenth century.

2.3 From the interpretation of structural damage to planning choices. Debate and construction in the eighteenth century

Just over sixty years after the rebuilding of the vault and of its lantern, the dome by Guglielmelli and, in particular, the first pillar on the left required the attention of Jesuits because of a worrying cracking pattern. A monitoring of this pillar was undertaken in 1767 using "swallow tails of marble" (Carrafiello 1995, p. 358) in correspondence with the above-mentioned pillar; at the same time, a first consultation with the royal architect Luigi Vanvitelli was carried out in order to have suggestions about appropriate remedies (Di Stefano 1973, p. 232).

The expulsion of the Jesuits from the Kingdom of Naples, which occurred in the same year, and the subsequent settlement of Reformed Franciscans in the church caused an interruption in the control of progression of the crackings and in Vanvitelli's task. Only from 1769 onward did the attention of engineers and religious focus again on the conditions of the building as the survey of 1769 by the architect Giuseppe Mauro demonstrates (Fig. 3). Beginning from 1769 the most accredited Parthenopean technicians of the second half of the eighteenth century were involved in the issues of the church. Among these, in particular, a decisive role was played in the choices by Ferdinando Fuga, who replaced Vanvitelli as the trusted technician of the Franciscans. Considering" azzardosissima" the solution of the rebuilding only the cracked pillar,

Figure 3. Naples, the Gesu Nuovo church. Front view ofthe second dome (1692-1693) drawn by the architect Giuseppe Mauro in 1769 (in Sasso 1856-1858, table 13).

Figure4. Naples, the Gesu Nuovo church. Hypothesis about the longitudinal section before the demolition of the second dome (from Guerra 1967, Fig. 5).

Figure 3. Naples, the Gesu Nuovo church. Front view ofthe second dome (1692-1693) drawn by the architect Giuseppe Mauro in 1769 (in Sasso 1856-1858, table 13).

Fuga proposed in 1769 a thickening of the structures of the four pillars in the crossing, of the upper arches and, in addition, of the remaining pillars and arches of the church resorting to "sottarchi" and "contropi-lastri" (Errichetti 1963, pp. 178-179). This proposal would have greatly expanded the resistant sections of the construction but, at the same time, it would have altered its space and the perception of the chapels and the tribune as provided for in the design ofValeriano.

The contradiction between eurythmia and the reasoning behind firmitas led, therefore, the Franciscans and the Royal Secretariat to require the formation of a team of experts in order to solve the problem; a committee composed of the Neapolitan professional intelligentsia, with Fuga himself, and with Mario Giof-fredo, Giuseppe Pollio, Giuseppe Astarita, Pasquale Monzo, Lorenzo Iaccarino, Felice Bottiglieri and Berardo Galiani, was formed in November 1769 in order to understand the causes and to propose a

Figure4. Naples, the Gesu Nuovo church. Hypothesis about the longitudinal section before the demolition of the second dome (from Guerra 1967, Fig. 5).

solution to the structural problems of the church (Errichetti 1963, pp. 178-179). During 1770 and the first half of next year, therefore, two "schools of thought" were gradually emerging through the direct examination of the conditions of the building; the first one can be considered much more "interventionist", while the other one was characterised by a more conservative approach. As we have seen, Fuga may be considered the exponent of the first approach, so that he would even propose the demolition of the aisles of the church, justified by economic reasons, in the following years (Errichetti 1963, p 181).

With respect to the issue, the royal architect Mario Gioffredo, planner and director of the construction of the complex dome of the Spirito Santo in the same years, would stand definitely on a more moderate front. Opposing Fuga's ideas, he supported the hypothesis of the recourse to only a partial substitution of the damaged pillar, avoiding more invasive interventions in this way. The position of Gioffredo coincided, with the appropriate distinctions, with the interpretations - in opposition to Fuga, as well - made by a young member of the technical Neapolitan class, Vincenzo Lamberti and, equally, by Berardo Galiani, author of the commented translation of Vitruvius De Architectura in 1758. The first, a young engineer who published the Voltimetria retta in 1773, ascribed the damage of the pillar and the dome to the actions of underground waters; he hypothesized an underpinning with arches near to the left pillar and a consolidation of the pillar with iron plates (Di Stefano 1973, p. 233). Lamberti, exponent of an emerging "theory of vaults" in the Neapolitan context, showed himself to be significantly abreast of studies conducted in other parts of Europe in the report he presented on that occasion (Guerra 1967, pp. 392-393); this, in particular, was in relation to the equilibrium of vaults and arches, as the quotations from de la Hire and Belidor demonstrate. This theoretical and cultural background was not enough, however, to avoid the answer, articulate and pragmatic, that Luigi Vanvitelli presented to the Secretariat of the Royal House in 1772 (Di Stefano 1973, pp. 233-234): sharing the idea of intervention of Ferdinando Fuga and removing the issue from "mathematical" interpretations, Vanvitelli brought the problem of the Gesu Nuovo church back to the direct examination of the phenomena. The architect attributed the main causes of the pillar's cracking and the causes of the damage still underway to the seismic tremors and to the excessive speed of past "restorations".

The position taken on the issue by Galiani seems equally interesting: a meditated approach to the constructive and dimensional characteristics of the building emerges from the report submitted by him in 1774, especially when the technician highlighted the existence of planning "repentances" in correspondence to the cross. He reported, in particular, the existence of a system of brick arches that had been constructed higher than the four tuff arches and connected with them through masonry plugs of poor quality. Galiani, like Lamberti and Gioffredo, excluded the possibility of an excessive load transmitted from the top dome on the four pillars and he rather attributed the damage to the thrusts of coverage structures on vertical walls (Carrafiello 1995, pp. 355-373). Despite the above described opposing positions, the majority of technicians involved in the question ended up attributing the damage underway to the excessive weight of the dome of Guglielmelli and to the poor quality of the construction; so, the demolition of the tambour and the higher vault was proposed in 1774. Started only in 1786, the intervention was carried out under the direction of the royal engineer Ignazio Di Nardo and it involved the replacing of the seventeenth century structures with a lighter "incannucciata" bowl (Fig. 5), sustained by a system of upper wooden beams (Errichetti 1963, pp. 181-183).

Di Nardo's intervention concluded, so, a significant phase in the history of the church's domes, characterized by the progressive reduction of covering masses and, consequently, of weights.

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