NARTHEX. An inclosed space in the ancient basilica when used as a Christian church; and also of an ante-temple or vestibule outside the church; it is thus used as synonymous with porch and portico. Some modern churches have a narthex with a lean-to roof, so as to form a kind of large porch the whole width of the building, or of the nave only. NATURAL BED OF A STONE. The surface from which the lamina were separated. In all masonry it is important to its duration that the lamina should be placed perpendicular to the face of the work, and parallel to the horizon, inasmuch as the connecting substance of these lamina is more friable than the lamina themselves, and therefore apt to scale off in large flakes, and thus in luce a rapid decay of the work. NAUMACHIA. (Gr. from Navs, a ship, and Maxn, a battle.) In ancient architecture, a place for the show of mock sea engagements, little different from the circus and amphitheatre, since this species of exhibition was often displayed in those buildings. One was erected at Milan under the orders of Napoleon I.

NAVE. (Gr. Naos.) The body of a church reaching from the rail or partition of the choir to the principal entrance. See CHURCH. By

far the most important feature of Romanesque architecture is the greater elevation obtained for the interior of churches beyond the mere walls of previous times. This resulted in the triple range of Pier arch, dividing the nave from the aisles, as 1 in fig. 1417; the Triforium, containing sometimes a gallery over the aisles, as 2; and the Clerestory, or row of windows admitting light to the nove, as 3. The string courses are unbroken, and give the appearance of the building being divided into layers or stages; the

arches also do not harmonise, and the whole Fig. 1417. Roman. Fig. 1418. Norman. presents the characteristics of the horizontality

of ancient types. The first stage of transition to the verticality of Pointed architecture

was the use of shafts of small diameter running up in front of the piers and dividing the

Fig. 1423.

Fig. 1424.

Fig. 1425.

Fig. 1426.

Fig. 1427. triforium and clerestory into compartments, as in fig. 1418. The style advanced, as is shown in fig. 1419, being an example of the treatment of a bay of a nave or choir in the Early English or Lancet period; fig. 1420 in that of the Geometrical Decorated; fig. 1421 in that of the Flowing or Late Decorated; and fig. 1422 in that of the earlier part of

the Rectilinear or Perpendicular period. In the later portion may be noticed the flatten ing of the arches, the four-centred arch being that most frequently used. The ogee arch (fig. 1427) was also much used at the same period. The above representations (figs. 1424 to 1427) of a bay of a nave or choir, exhibit the additions of a Perpendicular clerestory on a lower portion of earlier character; and the extinction of the triforium as a gallery, it being transformed into a wall decorated with panels. The priory church at Bath has not a triforium, but a lofty clerestory, like fig. 1426; while the choir at Bristol has neither triforium nor clerestory.

NEBULE MOULDING. (Lat. Nebula.) An ornament in Norman architecture, whose edge forms an undulating or wavy line, and introduced in corbel tables and archivolts. Fig. 1382. NECK OF A CAPITAL. The space, in the Doric order, between the astragal on the shaft and the annulet of the capital. Some of the Grecian Ionic capitals are with necks below them, as in the examples of Minerva Polias and Erechtheus, at Athens. But the Ionic order has rarely a neck to the capital,

NEEDLE. A horizontal piece of timber serving as a temporary support to some superincumbent weight, as a pier of brickwork, and resting upon posts or shores, while the lower part of a wall, pier, or building is being underpinned or repaired.

NERVURES. A name given by French architects to the ribs bounding the sides of a groined compartment of a vaulted roof, as distinguished from the ribs which diagonally cross the compartment.

NET MEASURE. That in which no allowance is made for finishing, and in the work of artificers, when no allowance is made for the waste of materials.

NEUTRAL AXIS. That plane in a beam in which theoretically the tensile and compressive forces terminate, and in which the stress is therefore nothing.

NEWEL. The upright cylinder or pillar, round which, in a winding staircase, the steps turn, and are supported from the bottom to the top. In stairs, geometrical for instance, where the steps are pinned into the wall, and there is no central pillar, the staircase is said to have an open newel.

NICHE. (Fr. probably from Neoroia, a nest.) A cavity or hollow place in the thickness of a wall for the reception of a statue, vase, &c.

NIDGED ASHLAR. A species of ashlar used in Aberdeen. It is brought to the square by means of a cavil or hammer with a sharp point, which reduces the roughness of the stone to a degree of smoothness according to the time employed. When stone is so hard as to resist the chisel and mallet, the method described is the only way in which it can be dressed.

NOGGING. A species of brickwork carried up in panels between quarters or studs, and in which manner partitions called "brick-nog partitions" are made.

NOGGING-PIECE. A horizontal board laid in brick-nogging, and nailed to the quarters for strengthening the brickwork. They are disposed at equal altitudes in the brickwork. NONAGON. (Gr.) A geometrical figure having nine sides and nine angles. NORMAL LINE. In geometry, one which stands at right angles to another line. NORMAN ARCHITECTURE. This term comprises the architecture of the Normans as seen in Sicily and adjoining countries; and is applied to the round arch style which was carried out chiefly in Normandy, and thence taken over into England soon after Edward the Confessor's time, and more prominently in the reign of William I. It is a variation of Romanesque architecture. See figs. 1417 and 1418.

NOSING OF A STEP. The projecting part of the tread-board or cover which stands before the riser. The nosing is generally rounded, so as to have a semicircular section; and in the better sort of staircases a fillet and hollow is placed under the nosing. NOTATION. In the early periods of the Roman notation, four was written IIII., this has been changed into IV.; nine was written VIIII., now IX.; forty was written XXXX, now XL. Five hundred was originally written I., now D.; a thousand CI., now M. The number I= 500, is increased in value ten times for every annexed. Thus I = 5,000; 1000=50,000, and so on. The number CIO=1,000 is increased in value ten tines for every C and 3 prefixed or annexed to it. Thus CCIO=10,000, &c. This notation is not now in use, but will be found in works of the 17th century. NOTATION, ARCHITECTURAL. The method adopted of placing signs to figures when marking dimensions on drawings. Thus, in lieu of writing feet, inches, and parts of an inch, certain dashes are used,' for feet," for inches, and "" for parts; or for feet,' for inches, and for parts. There is no settled method for using these marks.

NOTCH-BOARD. A board which is grooved or notched for the reception and support of the ends of steps in a staircase.

NOTCHING. A hollow cut from one of the faces of a piece of timber, generally made rectangular in section.

NUCLEUS. (Lat.) In ancient architecture, the internal part of a floor, which consisted of a strong cement, over which the pavement was laid with mortar.

NUGGER, OF NAGAR. The Sanscrit name for a city; as Ahmednugger, properly Ahmadnagar, the city of Ahmad.

NURAGHE. The name of a species of very ancient structure in Sardinia, resembling and used for a similar purpose as the cromlechs or doimens. They are supposed by some writers to be the work of the ancient Phoenicians.

NYMPHÆUM. (Gr.) A name used by the ancients to denote a picturesque grotto in a rocky or woody place, supposed to be dedicated to, and frequented by, the nymphs. The Romans often made artificial nymphæ in their gardens. In Attica, the remains of a nymphæum are still to be seen decorated with inscriptions and bassi-rilievi, from the rude workmanship of which it may be presumed that the grotto is of very ancient date.

OAK. (Sax. Ac, Ec.) A forest tree, whose timber is, from its strength, hardness, and durability, the most useful of all in building.

OBELISK. (Probably from òßeλòs, a spit, brooch, or spindle, or a long javelin.) A lofty pillar of a rectangular form, diminishing towards the top, those of Egypt often having inscriptions and hieroglyphics. The upper part finishes generally with a low pyramid, called a pyramidion. The proportion of the thickness to the height is nearly the same in all obelisks; that is, between one ninth and one tenth, and their thickness at top is never less than half, nor greater than three fourths, of that at bottom. The following table exhibits a list of the principal obelisks; and with the dimensions must be taken with some reservation. Builder, 1877, xxxv., 1076, gives a plate of eleven.

67.1

from Thebes: by Thothmes III. or IV.

Heliopolis only one now remains out of three pairs; it is the oldest,
by Osirtesen, about 3000 B.C.

London: Thothmes III., B.C. 1600; it was originally on a block of
granite 5.2 feet high, on three steps 6 ft. 6 in., pieds de Paris; re-
moved B.C. 23 to Alexandria; removed 1878 to London, and raised
for E. Wilson, by John Dixon, C.E.; called Cleopatra's Needle
Arles found buried there in 1389, and raised 1675

Paris: from Luxor; removed and raised 1831-36 by Lebas
Luxor: still there

2.7

2.6

1.9

2:4

3.9

5.1

8.1

59.7 & 50-0

67.2 & 69.1

OBLIQUE ANGLE. One that is greater or less than a right angle.

OBLIQUE-ANGLED TRIANGLE. One that has no right angle.

OBLIQUE ARCHES. Such as cross an opening obliquely to the front face of them.

OBLIQUE LINE. One which stands, in respect to another, at a greater angle than ninety degrees.

OBLONG. A rectangle of unequal dimensions.

OBSERVATORY. (Fr.) A building for the reception of instruments and other matters for observing the heavenly bodies. The observatory at Paris, from the designs of Perrault, is a noble building, but, we believe, is universally admitted to be very ill suited to the purposes for which it was built. A regular observatory is one where instruments are fixed in the meridian, whereby, with the assistance of astronomical clocks, the right

Ascensions and declinations of the heavenly bodies are determined, and thus motion, time, and space are converted into measures of each other. On the observations and determinations made in such establishments they are therefore, to maritime states, of vital importance, and ought to be liberally endowed by their governments. As the subject will be better understood by a plan, we subjoin, in fig. 1428, a plan and elevation of the observatory at Edinburgh. The general form of the plan, as will be therein seen, is a Greek cross, 62 feet long, terminated at its feet by projecting hexastyle porticoes, which are 28 feet in front, and surmounted by pediments. The intersecting limbs of the cross at their intersection are covered by a dome 13 feet diameter, which traverses round horizontally, and under its centre a pier of solid masonry is brought up of s

conical form 6 feet in diameter at the base, and 19 feet high. This is intended either for an astronomical circle or for an equatorial instrument for observations of the heavenly bodies made out of the meridian. In the eastern foot of the cross (bb) are stone piers for the reception of the transit instrument; c is the stone pier to which the transit clock is attached; and d is a stone piece on which an artificial horizon may be placed, when observations are taken by reflection: this is covered by a floor board when not in use, being just under the level of the floor; a a are the slits or chases running through the walls and roof, but closeable by means of shutters when the observation is completed. On the western side (e e) are chases as in the transit room; ƒ a large stone pier for the reception of a mural circle; g the clock pier; h the pier for an artificial horizon as before; i is the conical pier above mentioned, over which the moveable dome is placed, having an opening () in the elevation for the purpose of observation; k is the observer's room; and m the front entrance.

It is to be especially observed that the piers for the reception of the instruments must not be in any way connected with the walls of the building; they should stand on the firmest possible foundation, which, if at all doubtful, must be formed with concrete, and the piers should, if possible, be out of a single block of stone; but if that cannot be obtained, the beds must be kept extremely thin; partial settlement being ruinous to the nicety of the instruments as well as to the observer's business. The observation applies also to the clock piers, all vibration and settlement being injurious also to them. A dry situation should be chosen for the site, for, except in the computing rooms, no fire heat can be allowed; and it is important that the brass whereof the instruments are made should not be corroded by the action of moisture. In large public observatories there should be the readiest access from one part to another, and rooms for a library and computers independent of the chief astronomer's room. The Orwell Park observatory, as described by its architect, Mr. Macvicar Anderson, is published in the Sessional papers of the Royal Institute of British Architects, Nov. 16, 1874. The observatory at Warsaw by Pietro Aigner is said to be one of the finest in Europe; that at Armagh is very good. A descriptive account of public and private observatories in England is given in the Pictorial Handbook of London, 8vo., London, 1851, published by J. Weale. OBTUSE. (Lat.) Anything that is blunt.

OBTUSE-ANGLED TRIANGLE. One which has an obtuse angle.

OBTUSE ARCH. See DROP ARCH.

OBTUSE SECTION OF A CONE. Among the ancient geometricians a name given to the hyperbola.

OCTAGON. (Gr. 'OKтw and ravia, angle.) A figure having eight equal sides and eight equal angles.

OCTAHEDRON. (Gr.) One of the five regular bodies bounded by eight equal and equilateral triangles.

OCTASTYLE. (Gr. 'OKTW and ZTUλos.) That species of temple or building having eight columns in front. See COLONNADE.

ODEUM. (Gr.) Among the Greeks, a species of theatre wherein the poets and musicians rehearsed their compositions previous to the public production of them.

OECUS. See HALL.

OFFICES. The apartments wherein the domestics discharge the several duties attached to
the service of a house; as kitchens, pantries, brewhouses, and the like.
OFFSET. The horizontal projection from the faces of the different
parts of a wall where it increases in thickness.

OGEE. A moulding, the same as the CYMA REVERSA.
OGEE ARCH. A pointed arch, the sides of which are each formed
with a double curve. (See fig. 1429.) It frequently appears in
the Decorated period of Gothic architecture, and occasionally in
that of the Perpendicular; chiefly in small ornamental work,
as shrines and canopies; its inflected curves weaken it too much
for supporting great weights. In some late work, this arch is
also made to curve forward.

OGIVE. A term used by French architects to denote the Gothic
arch, with its ribs and cross springers, &c. The word is used
by them to denote the pointed arch.

OILLETS, or OYLETTS. Small openings or eyelet holes seen in medival military buildings, through which missiles could be discharged without exposing the soldier.

Fig. 1429.

ONE PAIR OF STAIRS. An expression signifying the first story or floor above that floor level with, or raised only by a few steps, above the ground, which latter is thence called the ground floor.

ONYX MARBLE. See MARBLE.