Editing St. Peter's Basilica (section)

====Michelangelo and Giacomo della Porta, 1547 and 1585====
[[File:St. Peter's Basilica Rome - 20140808 2350.jpg|thumb|St. Peter's Basilica from [[Castel Sant'Angelo]] showing the dome rising behind Maderno's façade|alt=Photo. The façade is wide and has a row of huge columns rising from the basement to support the cornice. The ribbed, ovoid dome is surmounted by a lantern topped with ball and cross. Its drum is framed by two very much smaller domes.]]
[[File:S. Pietro May 2022-15.jpg|thumb|The dome was brought to completion by Giacomo della Porta and Fontana.|alt= Photo looking up at the dome's interior from below. The dome is decorated at the top with a band of script. Around its base are windows through which the light streams. The decoration is divided by many vertical ribs which are ornamented with golden stars.]]

Michelangelo redesigned the dome in 1547, taking into account all that had gone before. His dome, like that of [[Florence]], is constructed of two shells of brick, the outer one having 16 stone ribs, twice the number at Florence but far fewer than in Sangallo's design. As with the designs of Bramante and Sangallo, the dome is raised from the piers on a drum. The encircling peristyle of Bramante and the arcade of Sangallo are reduced to 16 pairs of Corinthian columns, each of {{convert|15|m|ft}} high which stand proud of the building, connected by an arch. Visually they appear to buttress each of the ribs, but structurally they are probably quite redundant. The reason for this is that the dome is ovoid in shape, rising steeply as does the [[dome]] of Florence Cathedral, and therefore exerting less outward thrust than does a [[Sphere|hemispherical]] dome, such as that of the Pantheon, which, although it is not buttressed, is countered by the downward thrust of heavy masonry which extends above the circling wall.<ref name=BF/><ref name=JL-M/>

The ovoid profile of the dome has been the subject of much speculation and scholarship over the past century. Michelangelo died in 1564, leaving the drum of the dome complete, and Bramante's piers much bulkier than originally designed, each {{convert|18|m|ft}} across. Following his death, the work continued under his assistant [[Giacomo Barozzi da Vignola|Jacopo Barozzi da Vignola]] with [[Giorgio Vasari]] appointed by [[Pope Pius V]] as a watchdog to make sure that Michelangelo's plans were carried out exactly. Despite Vignola's knowledge of Michelangelo's intentions, little happened in this period. In 1585 the energetic [[Pope Sixtus V]] appointed [[Giacomo della Porta]] who was to be assisted by [[Domenico Fontana]]. The five-year reign of Sixtus was to see the building advance at a great rate.<ref name=JL-M/>

Michelangelo left a few drawings, including an early drawing of the dome, and some details. There were also detailed engravings published in 1569 by Stefan du Pérac who claimed that they were the master's final solution. Michelangelo, like Sangallo before him, also left a large wooden model. Giacomo della Porta subsequently altered this model in several ways. The major change restored an earlier design, in which the outer dome appears to rise above, rather than rest directly on the base.<ref>{{cite book |last1=De la Croix |first1=Horst |last2=Tansey |first2=Richard G. |last3=Kirkpatrick |first3=Diane |title=Gardner's Art Through the Ages |date=1991 |publisher=Thomson/Wadsworth |isbn=0-15-503769-2 |edition=9th |page=[https://archive.org/details/gardnersartthrou00gard/page/663 663] |url-access=registration |url=https://archive.org/details/gardnersartthrou00gard/page/663}}</ref> Most of the other changes were of a cosmetic nature, such as the adding of lion's masks over the swags on the drum in honour of Pope Sixtus and adding a circlet of [[finial]]s around the spire at the top of the lantern, as proposed by Sangallo.<ref name=JL-M/>

A drawing by Michelangelo indicates that his early intentions were towards an ovoid dome, rather than a hemispherical one.<ref name=Gardner/>  In an engraving in [[Galasso Alghisi]]' treatise (1563), the dome may be represented as ovoid, but the perspective is ambiguous.<ref>{{Cite book |url=https://books.google.com/books?id=qP5PAAAAcAAJ&q=Alghisi |title=Galassi Alghisii Carpens., apud Alphonsum II. Ferrariae Ducem architecti, opus |archiveurl=https://web.archive.org/web/20230403022925/https://books.google.com/books?id=qP5PAAAAcAAJ&q=Alghisi |archivedate=3 April 2023 |first1=Galasso |last1=Alghisi |first2=Dominicus |last2=Thebaldius |year=1563 |url-status=live}} pp. 44, 147 of Google PDF download.</ref> Stefan du Pérac's engraving (1569) shows a hemispherical dome, but this was perhaps an inaccuracy of the engraver. The profile of the wooden model is more ovoid than that of the engravings, but less so than the finished product. It has been suggested that Michelangelo on his death bed reverted to the more pointed shape. However, Lees-Milne cites Giacomo della Porta as taking full responsibility for the change and as indicating to Pope Sixtus that Michelangelo was lacking in the scientific understanding of which he himself was capable.<ref name=JL-M/>

Helen Gardner suggests that Michelangelo made the change to the hemispherical dome of lower profile in order to establish a balance between the dynamic vertical elements of the encircling giant order of pilasters and a more static and reposeful dome. Gardner also comments, "The sculpturing of architecture [by Michelangelo]&nbsp;... here extends itself up from the ground through the attic stories and moves on into the drum and dome, the whole building being pulled together into a unity from base to summit."<ref name=Gardner/>

It is this sense of the building being sculptured, unified and "pulled together" by the encircling band of the deep cornice that led Eneide Mignacca to conclude that the ovoid profile, seen now in the end product, was an essential part of Michelangelo's first (and last) concept. The sculptor/architect has, figuratively speaking, taken all the previous designs in hand and compressed their contours as if the building were a lump of clay. The dome ''must'' appear to thrust upwards because of the apparent pressure created by flattening the building's angles and restraining its projections.<ref name=Mignacca/> If this explanation is the correct one, then the profile of the dome is not merely a structural solution, as perceived by Giacomo della Porta; it is part of the integrated design solution that is about visual tension and compression. In one sense, Michelangelo's dome may appear to look backward to the Gothic profile of Florence Cathedral and ignore the [[Classicism]] of the Renaissance, but on the other hand, perhaps more than any other building of the 16th century, it prefigures the [[Baroque architecture|architecture of the Baroque]].<ref name=Mignacca/>