DOME. - It is a hemispherical vault of raised semicircular, depressed or pointed profile resulting from the rotation of polycentric curves, intended to cover a space of square, circular or polygonal plan resting directly on the perimeter wall or on internal supports independent of it by means of brackets, corner squinches or pendentives, or by means of a drum with or without windows. Apart from any consideration of the origin of the dome, which certainly had its greatest development in Roman architecture, all the types are already found in use in early Christian art for buildings of the centralized system, with the difference that supports independent of the perimeter wall prevail; the structure of the dome tends progressively to become lighter with the adoption of amphorae or fictile tubes, continuing a procedure already known to Roman builders. In Italy one may cite the examples of St. Costanza in Rome, the baptistery of Nocera dei Pagani, St. Lorenzo in Milan, the mausoleum of Galla Placidia, the two baptisteries and St. Vitale in Ravenna.
In Asia Minor, on the other hand, the dome is first inserted on the Anatolian type of basilica covered by a barrel vault and then on cruciform schemes; in the course of its evolution Byzantine architecture increasingly develops the drum pierced by windows and renders ever more complex the system for balancing the thrusts. The series of Constantinopolitan churches (Sts. Sergius and Bacchus, St. Sophia, St. Irene, St. Theodosia, St. John in Trullo, St. Mary Diaconissa, St. Mary Panachrantos, St. Mary Pammacharistos, St. Saviour in Chora) demonstrates the high degree of perfection reached by Byzantine builders.
In Italy in the Romanesque period the true and proper domes depend on Byzantine and Moorish models or influences and in that case show on the outside the extrados of the vault (St. Mark's in Venice, the cathedral of Pisa, St. Ciriaco and St. Maria in Porto Nuovo in Ancona, the cathedral of Caserta Vecchia, the cathedral of Molfetta, St. John of the Hermits, and St. Cataldo in Palermo, the Annunziata in Messina, etc.). In the longitudinal buildings of the Lombard type, being divided into segments and set on an octagon and not visible on the outside, they acquire rather the character of tiburia (v.). In the fourteenth century the prevalence of Gothic taste develops the tiburium almost to the limit of the irrational, so that in order to determine the internal space according to a precise geometric form it achieves effects of an entirely particular nature; of great interest therefore appears the plan of St. Maria del Fiore prepared for a dome-like covering over the central space joined to the triple nave. And at the beginning of the fifteenth century there arises the slender dome, of pointed section with a double shell held together by the ribs that bound the eight segments; the work still shows the influence of Gothic taste in various elements, but in the definition of a concluded and precise space it announces the new times. The dome planned instead by Alberti for the Tempio malatestiano, as appears from the medal of Matteo de Pasti, was a hemispherical shell on the model of the Pantheon. Domes multiply in the course of the fifteenth century; the Madonna dell'Umiltà in Pistoia, St. Maria delle Carceri in Prato, St. Maria delle Grazie al Calcinaio, St. Maria del Popolo and St. Maria della Pace in Rome are all inspired by a lively sense of line that accentuates their soaring quality and elegance.
With Bramante, both in the tempietto of St. Peter in Montorio and in the project for St. Peter's, the shell rests on the drum, losing all soaring quality, with a sense of weight that in the second case the drum pierced with a loggia would have accentuated. The history of the dome is summed up in that of St. Peter's, in which the Sangallesque project, by developing the drum until it partly hides the shell, gives it a development greater than a semicircle. Thus is prepared the triumphant Michelangelesque solution of a dome with a double shell which permits, besides a singular stability, a greater external soaring quality and a more coherent definition of the internal space, since the first shell is set somewhat lower. The plastic power of the drum serves effectively to buttress the thrusts of the double shell, while the ample breadth of the internal space dominates that of every other space, subordinating it to itself in a synthesis that permits no deviations. Beside the greatest sixteenth-century example one may recall those of the sanctuary of Loreto, of St. Biagio in Montepulciano, of St. Maria di Loreto in Rome, of St. Maria di Carignano in Genoa or of the Redentore in Venice, more adherent to the Bramantesque spirit than to the innovation of Michelangelo. But already in the Vignolesque Gesù in Rome the diameter of the dome becomes greater than the width of the nave, so as to strengthen with the curved lines of the backdrop the dynamic dilation of the internal space; on this path the Roman builders set themselves in the late sixteenth and seventeenth centuries, first among all Della Porta, to whom belongs the merit of having turned the double shell of Michelangelo's St. Peter's, not without some modification with respect to the master's definitive project. Then the timid shells set on elliptical plan are articulated into true domes according to a succession in which the architects working in Rome from Vignola to Francesco da Volterra and to Bernini and Borromini themselves stand foremost. The profile becomes even more complex and the drum is plastically articulated in St. Carlo ai Catinari, in St. Andrea della Valle or in St. Carlo al Corso in Rome; and in St. Ivo alla Sapienza Borromini composes the dome by continuing and joining the convex-concave sections of the perimeter structures with marvellous constructive daring. Then the dome tends to dominate with its mass the entire church conceived as its base, and the problem of barely perceiving at the entrance the internal space bounded by it determines various modifications of plan and elevation. Outside Rome the domes of Guarini, with their sources of light obtained in the shell or inserted between the two non-concentric shells, generate effects of singular scenography. With Juvara at Superga there is a return to the more composed and measured forms generally accepted in the eighteenth century.
Among the nineteenth-century domes heir to the tradition one may cite those of the Gran Madre di Dio in Turin, of St. Carlo in Milan, of St. Francesco di Paola in Naples, etc. Then the new technique, pushed to its extreme consequences, leaves in St. Gaudenzio in Novara a curious example of a drum with various superimposed orders that falls short of the purposes and effects required of a true and proper dome. With the manner of perceiving space changed, domes seem destined to decline with the prevalence of reinforced concrete; then from the formal multiplicity of nineteenth-century and modern eclecticism there have re-emerged new interpretations of Romanesque tiburia and finally still some domes in the wake of the sixteenth-century tradition. - See pls. LXIX-LXXII.
Bibliography4 works
17th and 18th Jahrhunderts in den romanischen Ländern (Handbuch der Kunstwissenschaft, 9, 1), Berlin 1915, passim; G. Giovannoni, La tecnica della costruzione presso i Romani, Rome 1921, passim; P. Toesca, Storia dell'arte italiana, I. Turin 1927, passim; N. Tarchiani, Architettura italiana dell'Ottocento, Florence 1937, passim; G. Giovannoni, Origini romane delle c. bizantine, in Atti del V Congresso interno, di studi bizantini, Rome 1940, passim (with bibliography); id., Tra la c. di Bramante e quella di Michelangelo, in Saggi sull'architettura del Rinascimento, Milan 1940, pp. 145-76; P. Sampaolesi, La c. di S. Maria del Fiore, Rome 1941; A. Verzone, L'architettura dei primi secoli cristiani nell'Italia settentrionale, Milan 1943; M. Zocca, La c. di S. Giacomo in Augusta e le c. ellittiche in Roma, Rome 1945; G. De Angelis d'Ossat, Romanità delle c. paleocristiane, ibid. 1946; G. Giovannoni, La c. di S. Pietro, ibid. 1947; V. Fasolo, La c. di S. Carlo ai Catinari, ibid. 1947; A. De Rinaldis, L'arte in Roma dal Seicento al Novecento, Bologna 1949, passim.