f POME. 



looad on them. The opening at UM top of the dome was decorated 

 with an ornamented broOM moulding, gilt. The external part of the 

 dome appear* abo to hare beta decorated with band* of brooie. Con- 

 .Untiiu II. removed the silver and broose with which the building 

 wa decorated. Tbe ban of the dome externally concilia of a large 

 plinth with aiz nnaller pUntht or step* above it ; and in the curve of 

 the dome a Bight of (top* U formed which lead* to the owning at the 

 top of the dome. From the drawing! uf the architect Serlio it appears 

 that flight* of (top* were formed at interval* all round the dome, 

 which are now covered with the lead placed there by order of Urban 

 VIII. The dome U constructed of brick, and rubble. Sunk band* 

 round the hollow aquare* or oai**on* appear to be formed in brick, and 

 the other part* in tufo and pumice stone. The thickness of the dome 

 of the Pantheon i* about 1 7 feet at the baae, 5 feet 1 4 inches at the 

 top of Uie higbwt itep, and 4 feet 7 inclien at the top of the dome. 

 Tbe circular wall which cupporU the dome is 20 feet thick. Thin 

 wall i* however divided by aeveral large openings, and is furnished 

 with discharging arches of brick. It is most probable that the dome 

 of the Pantheon was executed by meant of a centering of wood with 

 the hollow square* formed in relief upon it, as was afterward* done in 

 constructing the great vaulting of St. Peter's. 



The dume of one of the chambers of the Tin-nine of Caracalla van 

 111 feet in diameter. In the Thermic of Titus there are twn domc 

 each 84 feet in diameter, and in the bath* of Constantine there was 

 one of 76 feet. There were three domes in the baths of Diocletian, 

 of which two still remain ; one is 73 feet 6 inches in diameter, and 

 UM other 62 feet 3 inches. Judging from thoae that remain, there is 

 every reason to believe that in the Thermse they were all lighted from 

 above, like the dome of the Pantheon. Near Pozzuoli there is a very 

 perfect circular building, with a dome 96 feet in diameter, built of 

 volcanic tufo and pumice stone. The temple of Minerva Medico, 

 without the walls of Rome, was on the plan of a polygonal dome of ten 

 aides built of brick and pumice stone. This building doe* not appear 

 to have had any opening at the top. 



The ancients appear to have constructed domes on corbels. At 

 f>tni. there is a spherical dome which covers a square vestibule ; 

 and in one of the octagonal rooms of the enclosure surrounding the 

 bath* of Caracalla the corbels still remain which moat probably sup- 

 ported the dome of the chamber. 



The dome of Santa Sophia, at Constantinople, built in the reign of 

 Juxtinian, is the most remarkable and the earliest constructed after 

 those of the Romans. Authcmius of Tralles and Isidorus of Miletus 

 were the architect*. The present dome, however, wag reconstructed 

 by the nephew of Isidorus. It rests on the aquare formed at the 

 intersection of the arms of the Greek cross : the diameter is about 

 III feet, and the dome 40 feet high. The dome is supported by four 

 corbelling* placed in the angles of the square. The corbels are sur- 

 mounted by a kind of cornice which supports a circular gallery. The 

 lower part of the dome is pierced with a row of small windows 

 adorned with columns on the exterior. Externally the dome is 

 divided by projecting ribs, rounded and covered with lead. The top 

 U mrmountod by a lantern or finishing like a baluster, on which is a 



The dome of Anthemius and Isidorus was not so high, and 

 wu partly destroyed twenty -one years after it* construction by an 

 earthquake during the lifetime of Justinian. In the reconstruction 

 the nephew of Anthemius used very light white bricks, only one fifth 

 the weight of common bricks, which are said to have been made in 

 Rhode*, It appear* from the history and description of the building 

 of Santa Sophia, by Procopius, that the architects encountered many 

 difficulties, which arose probably from not being thoroughly acquainted 

 with the principles on which domes should be constructed. (Pro- 

 copius, f ft KTiapJcrttr, lib. i. cap. 1.) 



The dome of San. Vitale, at Ravenna, which is considered to be 

 more ancient than that of Santa Sophia, is curiously constructed. 

 The lower part of the plan of the dome in a regular octagon, which is 

 supported by eight pier* placed at the angles of the dome. Between 

 these angle* are seven tall niche* divided into two stories. The lower 

 part of these niches i* open, and ornamented with columns, like Santa 

 Sophia. The eighth side of the dome is pierced with a great arch 

 forming an entrance. This arch U of the same diameter and the same 

 elevation a* the niche*. The wall above the niches and arch, which i 

 without openings, sustain* a hemispherical dome, the plan being a 

 circle described within a regular octagon. Corbel* are not employed 

 as at Santa Sophia, but the arches support the gathering over, or cor- 

 belling, which forms the circular base of the dome. The base of the 

 dome u pierced with eight window*, each divided in the middle by a 

 column which supports two small arches. The dome itself i* built 

 with a double row of pipe*, hollow at one end and pointed at the 

 other, the point of one being placed in the hollow of the preceding. 

 They are thus continued in a gentle spiral line until they finish at the 

 top. Between the top of the small arched windows and the pipe* 

 there U a construction formed with vase*, not unlike the xystem 

 adopted in the circu* ( Caracalla. The dome iteelf is covered with 

 mortar both within and without. 



The church of San Marco at Venice, built in the 10th century, by 

 order of Pietro Oneolo, the then doge, i* decorated with five domes. 

 One of the**, placed in the centre of the church, i* much larger than 

 the other*. Each dome i enclosed within four piece* of *emi-cyliu- 



DOME. <08 



drioal vaulting, together forming a square, in the angle* of which arc 

 four corbel*, which gather in the circular baae of each dome. Tin- 

 lower part of the dome i* pierced with small windows. The intoi ior 

 u covered with moaaio, and the top of the dome is terminated with a 

 finishing on which is a cross. In 1 523 the doge, Andrea Gritti, caused 

 the dome* to be repaired, and Sansovino, the architect, restored in a 

 great measure the support*, and placed (at about one-third of its 

 height) a great circle of iron round the Urge dome to prevent its 

 falling ; a precaution which ha* been completely successful. The other 

 dome* are not *o well preserved. In 1729 one of the smaller dome* 

 was in danger of falling, from the decay which had taken place in a 

 circular bond placed at the base of the dome. Stone was however 

 ul, -muted for the wooden bond, and a i-ii. !< of iron placed without 

 ih.- dome near it* base. In 1735 Andrew Tirali, the architect to the 

 church, placed an iron circle round the dome which i* near the great 

 gate, on account of *ome small fractures which were then perceived. 

 If, however, the other domes are constructed with a wooden bond, it 

 is very probable that they will eventually fall unless steps be taken iu 

 time to remove the timber. By the use however of corrosive subli- 

 mate, now used in Ryan's patent for preserving wood from the dry 

 rot, wood may be used in the construction of domes with much more 

 security as regards durability. 



The celebrated dome of Santa Maria del Fiore, built by Bruneleechi, 

 is for superior in construction to the dome* of Santa Sophia and San 

 Marco. Bruneleschi first constructed the octagon tower which sup- 

 ports the dome. Each face of the tower is pierced with a circular 

 window ; the walls are 17 feet thick, and the cornice which terminate* 

 the tower is 175 feet from the ground. From this cornice rise* the 

 double dome. The outer dome is 7 feet 10 inches thick at the bale. 

 Tbe internal dome, which is connected at the angles with the external 

 dome, is 139 feet in diameter and 133 feet high from the top of the 

 internal cornice of the tower to the eye of the lantern. This dome 

 has eight angles, forming a species of Gothic vault, and was the first 

 double dome with which we are acquainted. Some time after the 

 dome was finished, several fractures were perceived in it, which were 

 owing to settlements in the masonry ; but the fractures were filled up 

 and no new signs of settlement have showed themselves since. 



The first modern dome constructed in Rome was that of the Church 

 of Our Lady of Loretto. It was commenced in 1507 by Antonio 

 Sangallo. The dome, which is double, is circular on the plan. The 

 internal dome is constructed on double consoles, instead of corbellings. 

 The double consoles are crowned with a small cornice, forming an 

 impost for eight arches, from the upper port of which springs the dome. 

 On the top is a lantern light, which is not apparent externally. 



Up to this time domes had been constructed on walls and corbellings ; 

 but in St. Peter's at Rome a new plan was adopted. The dome of 

 St. Peter's stands upon four piers, 61 feet 11 inches high, and 30 feet 

 10 inches thick, measured in a straight line with the arches. From 

 the arches spring the corbellings, which are finished by an entablature. 

 Upon this entablature is a plinth. The plinth ia externally an octagon, 

 and internally a circle. The external diameter of the octagon is 192 

 feet 9 inches, and the internal circle 134 feet 84 inches ; the thinnest 

 part of the wall, between the octagon and the circle, is 29 feet 8 inches. 

 On the plinth is a circular stylobate, 28 feet 64 inches thick. This 

 thickness is divided into three parts by a circular passage, 5 feet 10 

 inches wide : the two walls on each side of this passage are, respect i, < !y. 

 the internal wall 14 feet 74 inches thick, and the external 8 feet. Iu 

 the internal wall are other smaller passages, 2 feet 10 inches wide, 

 forming flights of steps communicating with the four spiral staircases 

 formed in the thickness of the wall of the drum of the dome. Above 

 the circular stylobate, which is 12 feet 44 inches high, is placed the 

 drum of the dome, which is 10 feet 1 J inches thick, measured to the 

 inside line of the pilasters, which decorate the interior of the dome. 

 The pilasters themselves are 178 feet thick in addition. The con- 

 struction U formed of rubble and fragments of brick. The interior is 

 lined with bricks stuccoed. Externally the work is faced with thin 

 slabs of travertine stone. The drum is pierced with sixteen windows, 

 9 feet 3 1 inches wide and 17 feet high. The walls are strengthened 

 on the outside, between the windows, with sixteen buttresses, con- 

 structed with solid mosonory. These buttresses are 13 feet 3 inches 

 wide and 51 feet 6 inches in height, from the base to the top of the 

 entablature. Each buttress is decorated and strengthened with half 

 pilasters, and terminates with two coupled columns engaged, the dia- 

 meter of which is 4 feet : the order is Corinthian. When the base of 

 the dome had been built to the height of the entablature of the drum, 

 Michel Angelo died : but some time before his death he had caused a 

 wooden model to be made, with ample details, to which he added 

 drawing* and instructions. After his death Pirro Ligorio and Viguola 

 were appointed the architects. Giacomo della Porto, the pupil of 

 Vignola, followed his master as architect to the cathedral ; but though 

 the designs of Michel Angelo were .-tri.tly followed, the dome itself 

 was constructed under the pontificate of Sixtus V. Sixtus gave Gia- 

 como della Porta as a colleague Domenico Fontona, by whom the 

 dome was constructed. 



On the constructions of Michel Angelo a circular attic was first 

 formed, 19 fi-.-t I'l in.-hes high, and 9 feet 7 inchw thick. This attic 

 is strengthened externally by 16 projections, 2 feet 11 inches deep, and 

 6 feet 44 inches wide, placed over the buttresses of the dome. On the 



