LACUNARIS, LACUNARIA or LACUNARS, in architecture, the panels of coffers formed on the ceilings of apartments, and sometimes on the soffits of the corona of the Ionic, Corinthian, and Composite orders.
In the temple of Minerva at Athens. the lacunars are placed immediately above the frieze within the portico, and formed with a siiTle recess, having an ovolo at the top, which moulding terminates the vertical plane sides, and the horizontal heads of the The lactinai•s are not square. but longer in the longitudinal than in the transverse direction of the building.
In this they are formed in one recess, with an ovolo at the top of the recess, or the farthest, extromit v of the sides. The lacunars are longer from ••ont to rear of the portico, than in the transverse direction of the building.
In the temple of Theseus at Athens, the lacunars are formed above the frieze, in two rows, between large beams which reach from the rear to the front of the pronaos : thei: figures are of a square horizontal section, and have only a single recess upwards, with an ovolo above it. The side of the square of each coffer is about one-fifth part of the diameter of the column, and their recess upwards of half the side of their square. The distance between the beams is equal to the breadth of the anta2 at the bottom, or nearly equal to the diameter of the columns. The beams are not regulated by the columns, but placed at equidistant intervals, to receive the two rows of lacunars, or coffers. Within the temple or cella, the beams reach transversely, from side to side ; but without, and under the soffit of the pronaos, they extend longitudinally from the front to the rear of the pro mos, and the laeunars in the same direction.
In the soffit of the temple of Pandrosus at Athens, the lacunars are formed immediately above the architrave, each into three recesses, with an ovolo at the bottom of each, nearly as broad as the perpendicular surface. The whole depth of
the recess is nearly half the side of the square of its lover part. Each part diminishes gradually in breadth in a sloping straight line, till the side of the square of the upper part is so contracted as to be only half that of the lower. Each succeeding third part diminishes regularly in altitude, so that, accounting the bottom the first, the altitude of the second, or the one next above, is something less, and the third about the same quantity less than the second. Each ovolo is something, less in height than the vertical surface below it, and has the same ratio to its respective surface.
The cella of the temple of Vesta at Rome is surrounded with a circular eolonnade. The ceiling of the portico leis a double row of lacunars, being two in the breadth of the por tico. The laeunars approach as nearly to a square as is con sistent with their diminution, formed by radiations towards the centre of the building, and are constructed in two recesses. The greatest breadth of the outside lacunar is about nine-thirteenths of the diameter of the columns. The whole depth of the recess upwards is about one-seventh of a diameter. The radiating sides are in vertical planes, and the other two sides of each are vertical cylindric concentric surfaces. The greatest breadth of the upper recess is about two-thirds of the lower. The hollow of this recess is occu pied by a rose of a circular form. The recess or cradle vaults of the temple of Peace at Rome are arched, and enriched with octagonal lacunars, each formed in three recesses, which diminish in their margins as they recede upwards. Between the octagonal lacunars are others of a square form in a diagonal position. The ceiling of the middle of the chapel of the said temple, is comparted with hexagonal and rhomboidal laeunars.
The laeunars of the arch of Titus at Rome are square, the side of each being about three-quarters of the diameter of the column.