order.

goods before they are in such a state as to identity and quantity as the buyer bargained to have them delivered in; but the above is the general rule. In general, also, the right of lien which the seller has against the buyer is not made away with by giving a dock-warrant or deliveryThe wharfinger or warehouseman is liable to an action if he refuses to comply with the dock-warrant or delivery-order and hand over the goods, provided he has signified his acquiescence in the order when it was first presented to him, or have accepted rent, &c, or done any other act so as to have assumed the character of wharfinger to the person suing. Various statutes have been passed for the better protection of persons making advances of money on goods, &c., on the security of documents of title of this kind, the last of which is the 5 & 6 Vict. c. 39; and see 12 & 13 Vict. c. 106, s. 179. DOCTOR, one who has taken the highest degree in the faculties of Divinity, Law, Physic, or Music. In its original import it means a person so skilled in his particular art or science as to be qualified to teach it. There is much difference of opinion as to the time when the title of Doctor was first created. It seems to have been established for the professors of the Roman law in the University of Bologna, about the middle of the 12th century. Antony à Wood says, that the title of Doctor in Divinity began at Paris, after Peter Lombard had compiled his Sentences, about the year 1151. (Hist. and Antiq. Univ. of Oxford, 4to. Oxf. 1792, vol. i. p. 62.) Previously, those who had proceeded in the faculties had been termed Masters only. The title of Doctor was not adopted in the English Universities earlier than the time of John or Henry III.

In Oxford the time requisite for the Doctor of Divinity's degree is eleven years from the time of matriculation, or four years from the time of proceeding B.A. Doctors of Civil Law, four years after proceeding through Arts, or if intending to practise in the Ecclesiastical Courts; if not, five years from the date of admission as B.C.L. For the degree of M.D., three years must intervene from the time of the candidate's having taken his Bachelor of Medicine's degree. For a Doctor's degree in Divinity or Law three distinct lectures are to be read in the schools, upon three different days: but by a dispensation, first obtained in convocation or congregation, all three are permitted to be read upon the same day; so that by dispensation a single day is sufficient in point of time for these exercises. For a Doctor's degree in Medicine, a dissertation upon some subject, to be approved by the Professor of Medicine, must be publicly recited in the schools, and a copy of it afterwards delivered to the Professor. The University fee on admission is 401.

In Cambridge a Doctor of Divinity must be a Bachelor of Divinity of five, or a M.A. of twelve years' standing. The requisite exercises are one act, two opponencies, a Latin sermon, an English sermon, and a determination. A Doctor of Laws must be a Bachelor of Laws of five years' standing. His exercises are two acts and one opponency. Doctors of Medicine must be Bachelors of Medicine of five years' standing, or a M.A. of seven years' standing. The exercises are two acts and one opponency. For the degree of D.D., the total fees are 51.; for LL.D., 25l. 108.; for M.D., 15. 10s. For a Doctor's degree in music, in both Universities, the exercise required is the composition and performance of a solemn piece of music, to be approved by the Professor of the Faculty. (Oxf. and Camb. Calendars,' for 1859.) Coloured engravings of the dresses worn by the doctors of the several faculties of Oxford and Cambridge will be found in Ackermann's History of the Univ. of Oxford,' 4to, 1814, vol. ii. p. 259, et seq.; and in his History of the Univ. of Cambridge,' 4to, 1815, vol. ii. p. 312, et seq.

DOCTORS' COMMONS, the College of Civilians in London, near St. Paul's Churchyard, founded by Dr. Harvey, Dean of the Arches, for the professors of the civil law. The official residences of the judge of the Arches' Court of Canterbury, of the judge of the Admiralty, and the judge of the Prerogative Court of Canterbury while it existed, were situated there; and it was the residence of the doctors of the civil law practising in London, who live there (for diet and lodging) in a collegiate manner, and common together. Doctors' Commons was burnt down in the fire of London, and rebuilt at the charge of the profession, whose modern representatives have been authorised to sell the property. [ARCHES, COURT OF.]

DODE'CAGON, a figure of twelve sides; a term generally applied to an equiangular and equilateral (or regular) dodecagon. [REGULAR POLYGON.]

DODECAHEDRON. [SOLIDS, REGULAR.] DOEGLIC ACID (CHO). An oleaginous acid, extracted from the oil of a species of sperm whale, Balana rostrata (Danish Dögling). It solidifies at 62° Fahr.

DOGE was the title of the first magistrate of the republic of Venice. The first settlers on the islands of the lagune were governed by magis trates sent from Padua. After Padua was devastated by the Huns and other barbarians, A.D. 452-60, the colonists of the lagune being left to themselves, each island elected a magistrate called tribune. An annual selection was made of seven from among these tribunes, who constituted the government of the whole community. A council of forty

persons chosen by the general assembly of the people had the legis lative and judicial powers. As population and wealth increased, and the community was threatened by hostile neighbours, it was found necessary to concentrate and strengthen the executive, and a chief magistrate for life was elected by the assembly of the people, and was called doge, a corruption of dux, as he was also general of the armed force. The first doge, Paolo Luca Anafesti, was elected in 697. The third doge in succession, Orso Ippato, elected in 724, made war against the Longobards, and took Ravenna, which he restored to the Byzantine emperor, who, as a reward for this service, granted to the republic a tract on the coast of the mainland as far south as the Adige. This first continental possession of Venice, being afterwards enlarged, was called Dogado. The successes of Orso inspired the people with jealousy, and he was assassinated in 737. The office of doge was at the same time abrogated, and an annual magistrate was substituted; but the fifth of these was imprisoned on some charge, and his eyes were put out, after which the people again elected a doge for life in 742. From that time till 1172 about forty doges ruled in succession, nearly one half of whom died a violent death, or were deposed, exiled, or had their eyes put out, sometimes by regular trial before the council of forty, and sometimes by popular insurrection. The Quarantia, or Council of Forty, which exercised the government during the interregna, assumed by degrees the power of electing a doge, in order to put a stop to the frequently recurring tumult and anarchy; the choice, however, was subject to confirmation by the assembly of the people. The first doge thus elected was Sebastiano Ziani, in 1173, and the Forty made him swear to a new constitution, or fundamental law, by which, instead of the general assembly of the people, the sovereign power was vested in a great council of 480 citizens, elected for one year, but capable of indefinite re-election. These were chosen by twelve tribunes, two for each sestiere, or district, of the city of Venice alone, who were themselves appointed by the inhabitants of their respective districts, the other islands and territories of the republic having no part in the elections; each tribune naming forty members. The Great Council was to appoint six individuals who were to be the doge's counsellors, without whose concurrence no act of the doge should be valid. This council was afterwards called "la Signoria." In important cases the doge was to consult with another council of sixty members, called Pregadi, or "requested," taken also from the Great Council. The citizens of Venice, weary of tumult, and being secured in the exclusive right of furnishing the members of the Great or Sovereign Council, seem to have willingly acquiesced in these constitutional changes, and a distribution of golden pieces made by the new doge served to gratify the populace. About a century after, another organic change took place. Pietro Gradenigo being elected doge in 1259, by the influence of the old or aristocratic families, proposed a law which passed the Great Council in 1298 after much opposition and delay, that no one should in future be eligible to sit in that assembly except those who then had a seat in it, or whose fathers, grandfathers, and great-grandfathers, had been members of it. The number of the members of the Great Council was no longer limited to 480. Lastly, in 1319, a new law passed the Great Council, by which that assembly declared itself permanent and hereditary, all the members who were then sitting in it (about 600 in number) remaining for life in possession of their seats, their sons who were above twenty-five years of age being likewise admitted, and their descendants after them, to the exclusion of all other families. This decree, known in history as "la serrata del maggior consiglio," established an hereditary and exclusive aristocracy at Venice, which lasted till the end of that republic. The celebrated Council of Ten was also then appointed, which, though at first only named for two months, gradually appropriated all the power of the state. confirmation of the doge by the people was henceforth dispensed with. The doge himself became merely a state pageant, the servant of the councils, which had the power of trying and deposing him, and even sentencing him to death. They took away from him the command of the military and naval forces, his children were excluded from every office of state, and he had no patronage except the prebendal stalls of the cathedral of St. Mark. The doge was president by right of all the councils, with a double, or casting vote. He was simply addressed by the title of Messer Doge. (Memori Venete' di Giovanni Gallicioli, Venice, 1826; Daru, 'Histoire de Venise,' books 6 and 39.)

The

The doges at Genoa were at first magistrates for life [BOCCANERA, in BIOG. DIV.], as at Venice, but the frequent contentions and civil factions among the aspirants to that dignity induced Andrea Doria, in his reform of 1528, to make the office of doge to last only two years. [DORIA, in BIOG. DIV.]

DOGMA (dóyμa), a word borrowed from the Greek, means an estab lished principle, a fundamental article of belief derived from undisputed authority, and is generally applied to the essential doctrines of Christianity which are drawn from the Scriptures, or from the authority of the Fathers. Hence that branch of divinity called dogmatic theology is an exposition and assertion of the various articles of the Christian faith as founded upon authority acknowledged by Christians in general, and is distinguished from scholastic theology, which assumes to estab lish the truth of the Christian doctrines by argument. John Damascenus was one of the first who wrote an exposition of Christian dogmatics. [DAMASCENUS, in BIOG. DIV.] But although the authority of the Scriptures and of the early fathers is acknowledged by all Christians,

there are other authorities which are acknowledged only by one communion, and not by others. Thus the Greek church acknowledges the authority of the earlier councils only, while the Roman Catholics look upon the later councils and the bulls and decretals of the popes as equally positive authority in matters of faith; and the Protestant and reformed churches, rejecting the latter, recur to their respective synods and confessions of faith. Melancthon wrote a concise exposition of the dogmas of the Protestant or Lutheran church. Among the numerous Roman Catholic writers on dogmatic theology, Bellarmine is one of the most distinguished. Dogmatic theology, as distinct from scholastic as well as from moral theology and Biblical divinity, constitutes a separate chair in several Roman Catholic universities in continental Europe, and in those of Ireland.

In the Protestant universities of Germany there is a chair for the history of dogmas. The business of the professor is to examine the doctrines of the various sects which have divided Christianity, their sources, and the arguments by which they are supported. Such a course of lectures forms an important addition to the study of Ecclesiastical History.

DOIT or DUYT, a small Dutch copper coin, being the eighth part of a stiver, in value half a farthing. Doit is also a division of the English grain Troy. See Snelling's View of the Coins of Europe,' 8vo. London, 1766. The word is used by Shakspere, Coriolanus,' Act i., sc. 5.

DOLLAR. [MONEY.]

DOME. The mathematical theory of a dome, so far as consideraions requisite for security are concerned, is more simple than that of

an arch. Imagine two vertical planes passing through the axis of a dome, and making a small angle with each other. These planes intercept (as in the cut) two symmetrically opposite slices of the dome, which tend to support each other at the crown. This support might be made complete and effectual upon principles explained in the article ARCH; so that in fact each small slice of the dome, with its opposite, might compose a balanced arch. Any slice of such a dome is supported by the opposite one only, so that all the rest might be taken away. Now suppose such a dome to be constructed upon an interior centering, of which however the arches are not separately balanced, in consequence of the weight of APK being so great that the resultant of this weight and the horizontal thrust at A falls obliquely, not being, as in a balanced arch, perpendicular to PK, but cutting the line K P produced towards the axis. Still this dome cannot fall: for since every part of the horizontal course of stones has the same tendency to fall inwards, these pressures inwards cannot produce any effect, except a lateral pressure of each slice upon the two which are vertically contiguons. Hence the condition of equilibrium of a dome is simply this, that the weight of any portion AMPK must be too great for a balanced arch. Upon the same principle a dome may even be constructed with a concave exterior: and in a dome of convex exterior a portion of the crown may be removed, as is the case when the building is surmounted by a lantern. The tendency of the upper part to fall inwards being equal all round, each stone is supported by those adjacent. From the preceding it appears that it would be (in comparison with an arch) easy to construct a dome with perfectly polished stones, and without cement. The friction of the stones and the tenacity of the cements are of course additional securities. The part in which the construction is weakest will be near the base, more particularly if the joints become nearly horizontal at the base, or if the circumference at the base be very considerable. This weak point is generally secured in practice by bringing strong chains or hoops round the horizontal courses at the interior of the base. Dr. Robison says, "The immense addition of strength which may be derived from hooping largely compensates for all defects; and there are hardly any bounds to the extent to which a very thin dome vaulting may be carried when it is hooped or framed in the direction of the horizontal courses." This system of internal hooping is every way preferable to reliance upon cements, and may, without interference with the ornamental part of the design, be carried to any length. Among other advantages, a dome may be made by means of it to rise vertically from the base, which cannot be the case in an arch.

For the demonstration of this formula, see Venturoli's 'Mechanics' (Creswell's translation), or Robison's 'Mechanical Philosophy.' It is not necessary that p should be a constant: a reference to the work first cited will show how to proceed on the supposition that it is a function of x greater than unity.

It is to be observed, however, that the mathematical theory of dome construction is utterly inapplicable to the extraordinary works of the Mohammedan architects, in which the curve of the dome itself is often carried considerably beyond the points of support. Evidently in such buildings as the Madrissa of Sultan Hussein at Ispahan, the Taj Mehal at Agra, or the tomb of Mahomet at Beejapore, given by Mr. Fergusson in his 'Handbook of Architecture,' the stability of the domes depends entirely upon the adhesion of the materials themselves; for if they had been free to move under the influence of gravity the domes must have fallen.

DOME (in Architecture). A term usually applied in England to express what more properly should be called a "cupola," or a spherical covering of a building or hall. The confusion in the use of this word seems to have arisen from the fact that the Italians and the Germans call the cathedrals, or principal churches of their towns by the generic name duomo, or dom, from the Greek Awua, as being the houses by way of distinction; and from the additional fact that the majority of the churches or cathedrals built in Italy since the revival of literature have been built with cupolas. It would now be impossible to bring the word back to its original signification, and it may therefore be considered that the term dome expresses generically the spherical or the spherico polygonal coverings of buildings, whether the plans of those buildings be circular or not; that is to say whether the spherical coverings be raised over a rotunda, or over a drum carried down by pendantives to a square base. Specifically the term dome expresses the outer, or the convex, side of the covering; whilst that of cupola expresses the inner, or the concave side.

Neither the Assyrians, Egyptians, nor the Greeks appear to have resorted to domical construction, although there were some rude attempts occasionally made by the latter nation, as in the treasure chamber at Mycenae, to carry out that mode of vaulting. The Etruscans seem to have been the first people who habitually employed the dome, and they very frequently adopted it in their tombs or their votive monuments. It was no doubt from them that the Romans derived this style of ornamentation; and it is certain that the most numerous ancient ruins of domes are to be found in the neighbourhood of Rome and Naples. The principal of these in and near Rome are the Pantheon and the temples of Bacchus, Vesta, Romulus, Hercules, Cybele, Neptune, and Venus, and also some of the chambers of the Thermæ.

The most magnificent dome of antiquity is unquestionably that of the Pantheon, supposed to be a chamber of the great baths of Agrippa. The diameter of the dome internally is 142 feet 8 inches, with a circular opening at the top in the centre 28 feet 6 inches in diameter. The height of the dome from the top of the attic is 70 feet 8 inches. Internally it is decorated with five rows of square compartments. Each row is considerably larger than that immediately above it, as they converge towards the top. The large squares, all of which are rather more than 12 feet each way, contain four smaller squares sunk one within the other. It is supposed that these squares were decorated with plates of silver, from some fragments of that metal having been

found on them. The opening at the top of the dome was decorated with an ornamented bronze moulding, gilt. The external part of the dome appears also to have been decorated with bands of bronze. Constantius II. removed the silver and bronze with which the building was decorated. The base of the dome externally consists of a large plinth with six smaller plinths or steps above it; and in the curve of the dome a flight of steps is formed which leads to the opening at the top of the dome. From the drawings of the architect Serlio it appears that flights of steps were formed at intervals all round the dome, which are now covered with the lead placed there by order of Urban VIII. The dome is constructed of bricks and rubble. Sunk bands round the hollow squares or caissons appear to be formed in brick, and the other parts in tufo and pumice stone. The thickness of the dome of the Pantheon is about 17 feet at the base, 5 feet 1 inches at the top of the highest step, and 4 feet 7 inches at the top of the dome. The circular wall which supports the dome is 20 feet thick. This wall is however divided by several large openings, and is furnished with discharging arches of brick. It is most probable that the dome of the Pantheon was executed by means of a centering of wood with the hollow squares formed in relief upon it, as was afterwards done in constructing the great vaulting of St. Peter's.

The dome of one of the chambers of the Therma of Caracalla was 111 feet in diameter. In the Thermæ of Titus there are two domes each 84 feet in diameter, and in the baths 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 the other 62 feet 3 inches. Judging from those that remain, there is every reason to believe that in the Therme 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 Medica, without the walls of Rome, was on the plan of a polygonal dome of ten sides built of brick and pumice stone. This building does not appear to have had any opening at the top.

The ancients appear to have constructed domes on corbels. At Catania there is a spherical dome which covers a square vestibule; and in one of the octagonal rooms of the enclosure surrounding the baths of Caracalla the corbels still remain which most probably supported the dome of the chamber.

The dome of Santa Sophia, at Constantinople, built in the reign of Justinian, is the most remarkable and the earliest constructed after those of the Romans. Anthemius of Tralles and Isidorus of Miletus were the architects. The present dome, however, was reconstructed by the nephew of Isidorus. It rests on the square formed at the intersection of the arms of the Greek cross: the diameter is about 111 feet, and the dome 40 feet high. The dome is supported by four corbellings placed in the angles of the square. The corbels are surmounted 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 is surmounted by a lantern or finishing like a baluster, on which is a cross. The dome of Anthemius and Isidorus was not so high, and was partly destroyed twenty-one years after its 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 Rhodes. It appears 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. (Procopius, TEрi кTIOμάтwv, 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 is a regular octagon, which is supported by eight piers placed at the angles of the dome. Between these angles are seven tall niches divided into two stories. The lower part of these niches is 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 is of the same diameter and the same elevation as the niches. The wall above the niches and arch, which is without openings, sustains a hemispherical dome, the plan being a circle described within a regular octagon. Corbels are not employed as at Santa Sophia, but the arches support the gathering over, or corbelling, which forms the circular base of the dome. The base of the dome is pierced with eight windows, cach divided in the middle by a column which supports two small arches. The dome itself is built with a double row of pipes, 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 pipes there is a construction formed with vases, not unlike the system adopted in the circus of Caracalla. The dome itself is covered with mortar both within and without.

The church of San Marco at Venice, built in the 10th century, by order of Pietro Orseolo, the then doge, is decorated with five domes. One of these, placed in the centre of the church, is much larger than the others. Each dome is enclosed within four pieces of semi-cylin

drical vaulting, together forming a square, in the angles of which aro four corbels, which gather in the circular base of each dome. The lower part of the dome is pierced with small windows. The interior is covered with mosaic, and the top of the dome is terminated with a finishing on which is a cross. In 1523 the doge, Andrea Gritti, caused the domes to be repaired, and Sansovino, the architect, restored in a great measure the supports, and placed (at about one-third of its height) a great circle of iron round the large dome to prevent its falling; a precaution which has been completely successful. The other domes are not so well preserved. In 1729 one of the smaller domes 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 substituted for the wooden bond, and a circle of iron placed without the dome near its base. In 1735 Andrew Tirali, the architect to the church, placed an iron circle round the dome which is near the great gate, on account of some 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 in time to remove the timber. By the use however of corrosive sublimate, now used in Kyan'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 Bruneleschi, is far superior in construction to the domes of Santa Sophia and San Marco. Bruneleschi first constructed the octagon tower which supports the dome. Each face of the tower is pierced with a circular window; the walls are 17 feet thick, and the cornice which terminates the tower is 175 feet from the ground. From this cornice rises the double dome. The outer dome is 7 feet 10 inches thick at the base. The 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 part 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 is externally an octagon, and internally a circle. The external diameter of the octagon is 192 feet 9 inches, and the internal circle 134 feet 8 inches; the thinnest part of the wall, between the octagon and the circle, is 29 feet 3 inches. On the plinth is a circular stylobate, 28 feet 6 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, respectively, the internal wall 14 feet 7 inches thick, and the external feet. In 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 4 inches high, is placed the drum of the dome, which is 10 feet 1 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 construction is 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 inches wide and 17 feet high. The walls are strengthened on the outside, between the windows, with sixteen buttresses, constructed with solid masonary. 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 diameter 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 drawings and instructions. After his death Pirro Ligorio and Vignola were appointed the architects. Giacomo della Porta, the pupil of Vignola, followed his master as architect to the cathedral; but though the designs of Michel Angelo were strictly followed, the dome itself was constructed under the pontificate of Sixtus V. Sixtus gave Giacomo della Porta as a colleague Domenico Fontana, by whom the dome was constructed.

On the constructions of Michel Angelo a circular attic was first formed, 19 feet 24 inches high, and 9 feet 7 inches thick. This attic is strengthened externally by 16 projections, 2 feet 11 inches deep, and 6 feet 4 inches wide, placed over the buttresses of the dome. On the

attic rises the double dome, the internal diameter of which, at the base, is 138 feet 5 inches. The curve externally is an arc of a circle whose radius is 84 feet 1.62 inches. To the height of 27 feet 8 inches from the attic the dome is solid. At the base the thickness is 9 feet 7 inches; and as the external dome is raised higher than the internal dome, the thickness is increased as the curve ascends, so that where the dome is divided the thickness is 11 feet 4 inches. The circular space which divides the two domes is 3 feet 2 inches wide; the internal dome is 6 feet 4 inches thick; and the height from the attic to the opening of the lantern is 83 feet 10 inches. The diameter of the lantern is 24 feet 10 inches. The external dome is 2 feet 10 inches thick where it separates itself from the internal dome; and it is strengthened externally by 16 projecting bands of the same thickness. The dome is pierced with three rows of small windows. As the curves of the dome are not concentric, the space between them becomes wider as it rises; so that at the opening of the lantern the space is 10 feet wide. These domes are joined together by 16 walls or spurs, diminishing in thickness as they ascend to the lantern; at the base they are 8 feet thick, and at the summit 3 feet. The base of the lantern is arched, and pierced with small windows. Above the two domes is a circular platform, surrounded with an iron gallery. In the centre rises the lantern, on a stylobate broken into 16 parts, forming projecting pedestals, above which are buttresses similar to the buttresses of the drum, decorated externally with coupled Ionic columns, 174 inches in diameter. The space between the buttresses is filled with arahed openings, which give light to the lantern. The external diameter of the lantern is 39 feet; the internal diameter 25 feet 11 inches; and the height from the platform to the top of the cross is 89 feet 7

inches. The whole height, from the external plinth of the dome to the cross, is 263 feet. The total height from the pavement is 437 feet 5 inches. The total height internally, to the top of the dome of the lantern, is 387 feet.

Sixtus V. covered the external dome with lead, and the bands with bronze gilt. One hundred thousand large pieces of wood were used in making the centering of the domes, which was so admirably constructed that it appeared suspended in the air. (See the drawings in the work by Fontana, on the construction of this dome.) This centering was more for the purpose of a scaffolding for the materials and workmen, than to sustain the weight of the double dome. During the construction of the dome it is believed that only two circles of iron were placed round the masonry, one of which was placed on the outside of the internal dome, at about 36 feet from its springing, and one foot above the division of the domes. The bands of iron of which this circle is composed are 3 inches wide by 1 inch thick. A similar circle is placed about the middle of the solid part of the dome, at about 17 feet 6 inches above the springing of the internal dome. Near the top of the internal dome there are several holes, at the bottom of which upright iron bars appear. These bars are said to be the connecting rods which keep together other circles of iron placed at different heights within the masonry, which are finally terminated by a circle round the eye of the dome.

The domes were constructed with such haste, that sufficient time was not allowed to the work to take a solid bed as it was carried up, in consequence of which a great number of vertical settlements have occurred, and the circle of iron round the internal dome was fractured. To obviate the danger arising from these settlements, six circles of iron

means eight supports are obtained instead of four, and the corbellings do not project too much, as in other similar constructions. The corbellings gather in a circle, the diameter of which is 104 feet 4 inches, the octagon base being 107 feet. The corbellings are surmounted by a complete entablature, 8 feet 3 inches high, decorated with consoles. The drum is set back 3 feet 24 inches from the face of the frieze, and this intermediate space is occupied by two steps and a seat. The cornice is 98 feet 9 inches from the pavement. The height of the drum from the top of the seat is 62 feet 6 inches to the springing of the internal dome. The wall forming the drum is inclined internally 4 feet 11 inches, or about the 12th part of its height. This was designed by the architect to increase the resistance of the walls to the united pressure of the large internal vault and the conical dome which carries the lantern.

The interior of the drum is decorated with a continuous stylobate, on which is an order of Corinthian pilasters. The 32 spaces between the pilasters are filled with 24 windows and 8 large niches. Externally the drum is decorated with an order of 32 Corinthian columns engaged, which are united to the wall of the drum by eight solid constructions in masonry. In each space between the constructions there are three intercolumnations, the columns being joined at their bases by walls pierced with arches. The external colonnade is surmounted by an entablature, with a mutuled cornice, on which is a balustrade; behind this is a terrace, formed by the recessing back. The attic is 22 feet 4 inches high from the top of the balustrade to the under side of the cornice of the attic. Above the internal order of the drum rises the interior dome, the diameter of which at the springing is 102 feet 2 inches by 51 feet in height. The top of the dome has a circular opening 14 feet 10 inches in diameter.

Above the attic are two steps, from which the external dome springs. The external dome is constructed of wood, covered with lead, and decorated with projecting ribs forming panels, curved at the ends. This dome terminates with a finishing which joins the base of the lantern; the circular gallery formed on the finishing is 274 feet 9 inches above the pavement of the nave. The lantern is supported on a conical tower, terminated by a spherical dome. This tower, which is joined to the internal dome at its base, disengages itself from it at the height of 8 feet 6 inches above the springing of the same. The perpendicular height of this tower is 86 feet 9 inches, and the walls are inclined 24 degrees from the perpendicular. The diameter of the base is 100 feet 1 inch measured externally, and 34 feet 1 inch at the springing of the spherical dome which finishes it. The wall of this tower is built of brick, and is 1 foot 7 inches thick, with circular rings of masonry, fastened with iron bands. The spherical dome at the top of the tower has an opening 8 feet in diameter at the summit. Between the attic and the wall of the tower are 32 walls or buttresses, which also serve to bear the ribs of the wooden external dome.

About the same time that Wren built the dome of St. Paul's, Hardouin Mansard, a French architect, constructed the dome of the Invalides at Paris. The plan of this dome is a square, in which is inscribed a Greek cross; in the angles of the square there are four chapels. The dome is raised in the centre of the Greek cross; the base supporting it is an octagonal figure, with four large and four small sides. The four small sides form the faces of the piers of the dome; the large sides are the arched openings of the nave and transverse aisles. A circular entablature is placed over the corbellings, and on the entablature is raised the drum of the dome, the diameter of which is 79 feet 9 inches. The interior of the drum is decorated with a continuous stylobate, above which are coupled pilasters of the composite order, and the wall is pierced with 12 windows. The dome, which is double, rises from a spinging common to both. The lower or internal dome, constructed with masonry, is spherical, and is 83 feet in diameter, with an opening or eye at the top 53 feet 3 inches in diameter, through which part of the outer dome can be seen. The outer dome is of a spheroidal form, and constructed of stone at the base and of brick above: Externally the dome is formed with a stylobate, on which is a Corinthian order of columns, over which is an attic with pilasters, and buttresses in the form of consoles. The drum is fortified externally by eight projections, placed two and two above each pier of the dome. The external dome is framed of wood and covered with lead, like St. Paul's, London, but the construction is much heavier. The external diameter of the dome is 85 feet 4 inches, and its height is 57 feet 2 inches. The finishing of the dome is decorated with consoles, on which is formed a circular balcony round the base of the lantern, constructed of wood, which is 39 feet 4 inches high; the lantern above it, with the cross, is 35 feet 4 inches high. The total height from the ground is 330 feet.

The dome of the Pantheon at Paris is constructed entirely of stone, and is placed in the centre of a Greek cross. It is supported by four triangular piers strengthened by engaged columns of the Corinthian order. The four piers with the lines of the intermediate arches form externally a large square, each side of which is 74 feet 9 inches.

These four piers are pierced above with arched openings, and between the piers with the openings are large arches, the diameter of which is 44 feet 11 inches, and the height 85 feet 5 inches. Between these arches rise the corbellings, which are gathered in to form the circular plan of the drum. The arches and the corbellings are crowned with a large entablature 13 feet 4 inches high. The upper part of the cornice

of the entablature is raised 101 feet above the pavement of the nave. The diameter taken at the frieze is 66 feet. The internal drum which is constructed on this entablature is 55 feet 7 inches in height to the springing of the internal dome. The interior of this drum is decorated with a continuous stylobate, which is the basement of a colonnade of 16 Corinthian columns almost isolated from the wall. These columns are 35 feet 2 inches in height. Between the columns are 16 windows, four of which are false, and placed above the four piers of the dome. The colonnade is crowned with an entablature, above which is a large plinth which rises to the springing of the internal dome. The internal dome is 66 feet 8 inches in diameter at the springing, and is decorated with octagonal caissons or sinkings with a rose in the centre of each. The eye at the top of the dome is 31 feet 3 inches in diameter. Through this eye is seen the upper part of another or intermediate dome. The external dome is placed on a circular base 108 feet 7 inches in diameter and square at the bottom. The angles are strengthened by flying buttresses. Above the corbellings a circular wall is constructed, forming an external continuous stylobate which supports an external colonnade. The external colonnade constructed on the stylobate forins a peristyle round the dome, and is composed of 32 isolated columns of the Corinthian order 36 feet 5 inches high. This colonnade is divided into four parts by the solid constructions in masonry raised over the four piers. The external colonnade is surmounted with an entablature and balustrade above it. There is an attic constructed above the circular wall of the drum, set back 13 feet 10 inches, and pierced with 16 windows, 12 of which light the space between the internal dome and the intermediate dome which bears the lantern. This attic is terminated with a cornice with a step or plinth above. The external dome, 77 feet 8 inches in diameter, measured on the outside, is constructed with masonry; the height is 45 feet 9 inches from the top of the attic to the underside of the finishing against which the curve terminates. The outside of the dome is covered with lead, and is equally divided vertically by 16 projecting ribs. The intermediate dome, built for the purpose of carrying the lantern, was intended to be decorated with subjects by the painter, and we believe it has since been decorated. The form of this dome resembles the small end of an egg: its springing commences at the base of the attic at the point where the internal dome begins to disengage itself. This dome is 50 feet 3 inch high, and 70 feet 3 inches in diameter, and is pierced with four great openings at the lower part 37 feet 3 inches high, and 30 feet 10 inches wide at the base. On a circular platform above the summit of the dome are eight piers with arches, which support the finishing against which the external dome terminates. Above this is the lantern of the dome.

Very full details of the most remarkable domes in Europe are given in the Encyclopédie Méthodique' (article Architecture), from which this brief notice is in a great measure taken. For an account of the construction of wooden-ribbed domes, see Nicholson's 'Architectural Dictionary;' also the section of the Pantheon dome by Taylor and Cressy; also the work on St. Peter's, by Fontana. The dome of the Reading Room of the British Museum is described in the article BRITISH MUSEUM.

The following admeasurements of most of the principal domes of Europe are chiefly from Mr. Ware's 'Tracts on Vaults and Bridges':— DOMES OF ANTIQUITY.