7,851,963 inches, wrong only by one part out of 3890. Therefore, for every practical purpose, an arc of a circle (and the same may be said of every other curve) is the polygon made by the chords of a moderate number of subdivisions of the arc. The preceding property is (but in what manner our limits will not permit us to show) a consequence of the following proposition. Let there be a number of arcs, such as A CB, cut off the same curve, having their chords parallel to the tangent X CY; then, as A B moves parallel

to its first position towards XY, CD not only decreases without limit but its proportion to A B decreases without limit; that is, let any number, however great, be named, then shall A B, before it reaches XY, reach a position in which it contains CD more than that number of times. This proposition is startling to the beginner in mathematics, and should be considered by him with great attention. It may be illustrated in the following manner :-Suppose that while A B moves from its first position towards X Y, and has reached ab, a miscroscope moves with and over it, which increases in magnifying power as ab moves, in such a manner that ab always appears in the glass as large as A B to the naked eye. Then a cb will not be magnified into the form A & B, but into A Q B, where QD grows less and less without limit, as ab approaches towards XY. But if two straight lines had been taken, as in the following figure, ab could not have been magnified to A B without changing a cb into a CB.

Formerly, the term arc was frequently confounded with angle, which arose from the practice of measuring angles by arcs of the circle. For such terms as ARC OF ELEVATION, &c., we refer to ANGLE OF ELEVATION, &c.

ARCADE signifies a series of arches on insulated piers, forming a screen, and also the space inclosed by such. This is, perhaps, a limitation of the term within that usually given to it; but arcade is properly a correlative of colonnade, and should not therefore have a more extensive signification. What, by a strange perversion of the term, are in this country called piazzas, and most particularly the part so termed of the buildings in Covent Garden, London, are strictly arcades; and the market within the inclosed area of that same place or square, to which the term piazza properly applies, exemplifies, in a great part of its exterior, the correlative term colonnade.

In Gothic architecture the term arcade is applied to a series of arches supported on piers, and used as decorations for the walls of churches, and occasionally of other buildings. The arches are sometimes open, but more commonly closed by the masonry of the wall. Good examples of arcades of the Norman and Early English styles (in which arcades are most employed) occur in Canterbury cathedral; of the decorated style in Lichfield cathedral: but most of our cathedrals possess some examples.

In addition to its proper technical meaning, this term has acquired a different signification among us as the popular name for what the Parisians more properly designate a 'passage' or 'galerie,' namely, an alley lined on each side with shops, and roofed over so as to be in fact a sort of 'in-door' street, entirely protected from the weather, and of uniform design throughout in its architecture. So far, an arcade answers to the idea of a bazaar, the chief distinction between the two being that the latter has not so much of street character about it, but consists either of a single spacious hall or separate rooms, fitted up with counters and stands, and may therefore be likened to a single large shop occupied by a number of different dealers, whereas in an arcade the shops are quite distinct from each other, and enclosed in front with windows after the usual manner; and they have besides dwelling accommodation, kitchen, &c., beneath, and a chamber over them, with the addition sometimes of an entresol. Another distinction is that an arcade serves as a public thoroughfare for foot-passengers. The Burlington Arcade, which was the first place of the kind in London, has indeed little more than its convenience as a thoroughfare and promenade for foot-passengers to recommend it, inasmuch as it makes no pretensions to elegance of design, nor has it anything in accordance with the title bestowed on it, it being neither arcaded in any way nor arched over. The Lowther Arcade in the Strand (erected 1831) manifests a great improvement upon that first specimen, for it is really a handsome piece of architecture; the side elevations are divided by

pilasters into compartments, each of which contains a shop-front, with an ornamented triple window over it, and above that a semicircular one in the arched head of the compartment. On the plan, each of these divisions is covered by a pendentive dome with a circular skylight; and these numerous domes and their arches produce a pleasing perspective effect. Three other arcades have been opened in London since the erection of the Lowther Arcade. The first of them, Exeter Arcade, running from Wellington Street to Catherine Street in the Strand, erected in 1844 from the designs of Mr. Sidney Smirke, is very short; is more enclosed than either Burlington Arcade or Lowther Arcade; has a vestibule at each end; is glazed, so that the lights form a continuous skylight, and has polychromic embellishment applied both on the upper part of the walls (in ornaments and panels between the windows over the shops) and on the cove of the ceiling. The whole place has indeed more the appearance of a hall or gallery than of a place of thoroughfare and business. The arcade in New Oxford Street, opened in 1851, is short but of rather pretentious character. Both of these have proved commercially unsuccessful, and neither is, in fact, now employed for the purpose for which it was constructed. The South-Eastern Arcade, at the entrance of the South-Eastern Railway Station, London Bridge, is only remarkable for its unmitigated architectural baldness and poverty. In Paris arcades have obtained much greater popularity than in London. Among the Parisian arcades, the Passage Colbert is one of the most striking, both for its extent and architectural display, towards which last its Rotunda contributes in no small degree.

ARCH. The origin of that species of construction called an arch is unascertained; it cannot be stated with certainty either in what country or at what epoch it was first used. There is good reason to think that, though the arch form was certainly known to the Pelasgic inhabitants of Greece, it was unknown to the Greeks at the time when they produced their most beautiful temples, in the fifth, fourth, and third centuries before the Christian era. No structure answering to the true character of an arch has been found in any part of those works, though many occasions occur in which the application of the arch would have been of great service, and would seem unlikely to have been passed over by an intelligent and ingenious people like the Greeks if they had been acquainted with the principle. The want of the arch would necessarily lead them to contract the intercolumniation, or spaces between the columns, and to the general and frequent adoption of columns as the only mode of supporting a superstructure. But though not appropriated--at least for their sacred buildings-by the Greeks, it is now certain that the arch was known both to the Egyptians and the Assyrians. There are brick arches at Thebes in Egypt, which belong to a very remote epoch, and one long prior to the Greek occupation of that country. Minutoli (Reise zum Tempel des Jupiter Ammon') has given two specimens of Egyptian arches, one of which is a false and the other a true arch. The first specimen is from the remains at Abydos in Egypt (p. 245), where the roof has the appearance of an arch, but is formed by three horizontal stones, of which that which occupies the centre and lies over the other two is the largest; the three stones are cut under in such a way as to form a semicircle. The true specimens are at Thebes (at least as early as B.C. 1490), on the west side of the river (p. 260), near and behind the building which contains the fragments of the enormous statue. They are circular arches, and formed of four courses of bricks (see pl. 29), and on the walls there are Egyptain paintings and hieroglyphics. (See also Belzoni's Plates,' No. 44, and his remarks on the brick arches of Thebes; and also Sir Gardner Wilkinson's Egypt and Thebes,' pp. 81 and 126; 'Manners and Customs of the Egyptians,' vol. iii.; and Colour, p. 297.) The stone arches in the Nubian pyramids can hardly perhaps be adduced in proof of the early use of the arch, as these edifices are probably not of very high antiquity (see Cailliaud's 'Plates,' No. 43), though Mr. Hoskins (Travels in Ethiopia') attributes to the latest of them a date not more recent than that of Cambyses. A stone arch of a date not later than that of Psammeticus has been discovered at Saccara, and another in a tomb near Gizeh. Mr. Layard and M. Place found both round and pointed arches at Nimroud and at Khorsabad, the construction of which shows that the ancient Assyrians were at a very early period sufficiently acquainted with the constructive value of the arch to apply it to a variety of important purposes. In the roofs of the tombs of Lycia, of about the 5th century B.C., the pointed arch occurs. (Fellowes' Lycia;' and the works of Forbes and Spratt.) Etruria seems, from the best evidence that can be obtained, to have been the first place in Europe where the arch was employed; and to the Etrurians may be assigned the honour of its earliest applications, as far as our positive and undisputed information goes, in works of an important size and character, in a pointed as well as in the circular form. The great sewer of Rome, commonly called the Cloaca Maxima, is an arched construction, which can hardly be referred to any period in the history of the city with so much probability as to that to which it is assigned by uniform tradition, namely, the age of the Tarquins. But though we may readily admit this early date, we cannot say whether the architects were Roman or Etrurian, though the latter would seem the more probable.

The application of the arched structure is one of the most useful mechanical contrivances ever discovered by man. By means of it, small masses of burnt clay, and conveniently sized pieces of soft and friable sandstone, are made more extensively useful for the economic

purposes of building, than the most costly and promising materials were in the hands of the Greeks. By means of it, cellars are vaulted; subways, or sewers, are made to pass under heavy structures and along streets with certainty and safety; and secure and permanent road-ways for every purpose of communication are formed across wide, deep, and rapid rivers. Extensively as they made use of the arch, the Romans did not deviate much from the semicircular form. Arches of smaller segments were certainly used by them, as well as elliptical arches, but in these cases they were fortified with enormous abutments, which proves that the architects, who probably in nearly all cases were Greeks, knew very well the weak points of such a construction. It was reserved for the architects of the middle ages, or rather those of the 12th, 13th, and 14th centuries, to show what could be done by varying the form and construction of the arch.

The pointed arch, upon its invention or first introduction into Europe, seems to have exercised the ingenuity of architects in varying its form and application. This we observe in the numerous ecclesiastical structures in this country, in our beautiful pointed styles, and most particularly in some of the greater churches and cathedrals.

The origin of the pointed arch has been almost as much disputed as the discovery of the principle of the arch itself. It became general in most parts of Europe at nearly the same time, and about the period of the return of the warrior-priests and pilgrim-soldiers of the First Crusade. This, and other circumstances which might be adduced, added to the well-ascertained fact of the pointed arch being used among the Eastern nations before that period, it was certainly used by the Arabs in their mosques in the 9th century, and it occurs in the church built over the Holy Sepulchre in the reign of Constantine-and that an arch of the pointed form was not known to have been used in the northern and western parts of Europe anterior to the first crusade, gave, in the opinion of some French as well as English authorities, a reasonable degree of certainty to the supposition that the notion was brought from the East by the crusaders. But it is pretty certain that the pointed arch was in use in ecclesiastical architecture in some parts of France prior to the return of the first crusaders; and, as is observed by Mr. Fergusson ('Handbook of Architecture,' ii. 598), we need not feel surprised that a people trading with the Levant from their great port of Marseilles, should have thence borrowed this feature; or perhaps we might rather say, that a people descended from a colony of Pelasgic Greeks should revive an old and time-honoured form when they found it particularly suited to their constructive purposes. So remarkably suitable indeed was it, that we should not wonder even if they had actually invented it de novo." Indeed, after all that has been said and written on the subject, it seems most likely that the pointed arch grew out of the exigencies of early ecclesiastical architecture. As Mr. Rickman long ago pointed out, the Norman style was constantly assuming a lighter charater; intersecting arches were a usual mode of embellishing Norman buildings, and they, or the arches formed in vaulting, would have suggested the pointed form,—if, as has been truly said, the mere ordinary use of a pair of compasses had not been sufficient to suggest it, and once suggested, its superior lightness and applicability would insure its employment. Its diffusion from the centre of ecclesiastical architecture evidently requires no explanation. But, as Sir Gardner Wilkinson very truly observes, the pointed arch was assuredly "neither exclusively, nor even originally Christian."

The various forms and decorations of the arch will be found under the several divisions indicated in the article ARCHITECTURE; see especially GOTHIC ARCHITECTURE.

ARCH, the same word as arc in its etymological derivation, and an older English form (having been always used in the sense of arc until that continental form superseded it), is now applied to any solid work, whether of masonry or otherwise, of which the lower part is formed into an arc of a curve supported at the two extremities. We proceed to give some idea of the question of theoretical mechanics connected with this word, referring, for all matters connected with the support, to ABUTMENT, BUTTRESS, IMPOST, PIER, and for history and general information to BRIDGE.

In practice, we have not only the arch itself to consider, but the Joose matter with which the space above it is filled, and the roadway or building thereon constructed. The two extreme effects of this load may be thus stated. If it were fluid, the common law of hydrostatics cd

Fig.1

8 h

would direct us to consider every small portion ab (fig. 1) of the arch in sustaining a Į res are erpendicular to itself, equivalent to the weight

of a column of fluid having the horizontal base ab, and the mean of a c and bd for its altitude. On the other hand, if the whole superincumbent load could be considered as perfectly solid and wholly unsustained by lateral pressure, the portion pqhg might be considered as a part of the arch-stone underneath. In the absence of all trustworthy experiments to determine how far the real superincumbent pressure, where resulting from loose materials, partakes of one or the other supposition, we shall adopt the latter as probably nearer the truth than the former: which is equivalent to treating of the arch only after its superincumbent weight has been added to each arch

stone.

A C and B D are called the piers of the arch; it is said to spring from A and B; AE and B F are the haunches, and G the crown or keystone. The lower line of the arch stones is called the intrados or sojat, the upper, the extrados or back; the arch-stones are called voussoirs, and the highest stone, G, the key-stone. AB is the span or chord of the arch, and G H its rise, or versed sine. The voussoirs are cemented together, and if the cement were sufficiently strong, any form might be given to the arch, or at least any form which would stand if cut out of the solid material. If we suppose the stones uncemented, their friction upon one another would tend to prevent the disturbance of equi librium, and allow considerable variety of form in arches constructed with stones of the same weight. But if we suppose the stones perfectly smooth, so that each of them is kept from slipping only by the pressure of the adjoining two, then each intrados ought to have one particular form of extrados, and one only, so long as the manner in which the stones are cut follows one given law.

Let PQ, RS (fig. 2) be parts of the pier, which we suppose firmly fixed, and let there be no key-stone, or suppose the key-stone divided

in the middle at AB. Let the portion ACDB be taken, composed of several arch-stones, and let its centre of gravity be G. Then the weight of ABCD, collected at G, is sustained by pressures at the surfaces A B and C D, perpendicular to those surfaces. Take EF in the continuation of A B, of any length, and draw F H parallel to CD. It is a known theorem, that any three forces which balance each other are proportional to the three sides of a triangle, the directions of the sides of which are perpendicular to the direction of the forces. In the present case, H E F is such a triangle; for H E, being horizontal, is perpendicular to the direction of all weights; FE is the continuation of AB, and therefore perpendicular to the pressure at AB, while F H, being parallel to CD, is perpendicular to the pressure at CD. Hence HE bears to EF the same proportion as the weight of ACDB to the pressure at A. In the same manner it may be shown that, F м being parallel to KL, the weight of the portion A B K L is to the pressure at A B as ME to EF, from which it follows that the weight of A KLB bears to that of ACDB the proportion of M E to H E. Hence the following theorem: S R Q P NM E

F

Let EF be vertical, E s horizontal, and FM, FN, &c., parallel to the divisions between the voussoirs of an arch which is divided at its highest point: then, no friction being supposed, there can be no equilibrium unless the weights of the successive voussoirs, reckoned from the highest point, are to one another as E M, M N, NP, &c.

........

It is also necessary to the equilibrium of the arch that the vertical drawn through the centre of gravity G of the part ACDB should cut the parallelogram 1 2 3 4, made by perpendiculars to AB and CD drawn from their extremities: for otherwise there would be no point in the vertical through G (at some part of which the weight must be supposed to act), at which the directions of the perpendicular pressures could meet, and no three forces can maintain equilibrium unless their directions pass through one point.

1

An arch constructed upon the preceding principles would, if the stones were perfectly smooth, be totally overturned by the least

X

A

R

D

addition to, or subtraction from, the weight of any one arch-stone : for each arch-stone is only just kept in equilibrium by the pressures of the two adjoining. Such an arch, therefore, would not serve for a bridge, which must bear a considerable addition to its weight at different times. It is to the friction and cements that the power of sustaining additional weights is due. It is evident that before the arch, kept in equilibrium as above, can be overturned, the additional pressure must be such as to overcome the friction against some one arch-stone exerted by the two adjoining. And the advantage is the greater, since the additional pressure itself increases the friction which opposes it. The effect of friction may be thus represented. First ascertain the extreme angle at which a mass of stone, such as the arch is to be built of, would rest upon an inclined plane of the same material: that is, raise the stone A upon the stone plane B O until the least additional elevation would make it slide down. Measure the angle C B D. Now suppose P Q R S T V to be part of an arch kept in equilibrium without friction. From T on both sides make the angles QTX, QTY equal to CBD above measured: then the effect of friction is this, that instead of the two arch-stones meeting in TQ, their line of junction might have been anywhere in the angle Y TX, without endangering the mere equilibrium. Or if, as in a preceding figure, F M and F N are parallel to the lower sides of two arch-stones, and the angles M F X, MFY, NF X', NFY', be made equal to the angle B C D above measured, then, instead of its being required that the proportions of the weights resting on those sides should be strictly that of EM to EN, they may be in the proportions of any two lines, which, being set off from E towards s, have the end of the first between X and Y, and that of the second between x' and y'. The great latitude which this gives to F the construction (since B C D is, for some materials, as great as 40°) renders attention to the system of equilibration without friction almost unnecessary, so that any arch which does not very materially differ from the arch kept in equilibrium without friction may be considered as safe from all fracture which arises from the slipping of an arch-stone.

P

S

T

B

YN X

YM X

V

E

The difficulty in the way of determining the best figure of an arch, lies in our comparative ignorance of the manner in which pressure is actually communicated. The materials supposed in mechanical problems are usually perfectly rigid; those of nature are compressible: and though it is clear that a very slight alteration of form might throw the pressure of one arch-stone almost entirely upon a very small part of the adjoining stone, we do not know enough of the nature of building materials even to guess at the law of distribution of pressure. Again, if a part of an arch be overloaded, but prevented from falling by the friction or cement, a new force, not contemplated in the preceding theory, is exerted upon the remainder. Dr. Robison, as far as we know, was the first who brought forward this method of considering

the subject. He was led to it by observing an arch which fell, the account of which we give in his own words (Mechanical Philosophy,' vol. i. p. 640): "It had been built of an exceedingly soft and friable stone, and the arch-stones were too short. About a fortnight before it fell, chips were observed to be dropping off from the joints of the archstones, about 10 feet on each side of the middle," that is at H and F, "and also at another place on one side the arch, about 20 feet from its middle," that is at I and G. "The masons in the neighbourhood prognosticated its speedy downfall, and said it would separate in

those places where the chips were breaking off. At length it fell: but it first split in the middle, and about 15 feet or 16 feet at each side," that is at D and B, “and also at the very springing of the arch," that is at k and l. 66 Immediately before the fall, a shivering or crackling noise was heard, and a great many chips dropped down from the middle between the two places from whence they had dropped a fortnight before," that is from a and b. "The joints opened above at these new places more than 2 inches, and in the middle of the arch the joints opened below, and in about five minutes after this the whole came down. Even this movement was plainly distinguishable into two parts. The crown sunk a little, and the haunches rose very sensibly, and in this state it hung for about half a minute. The archstones of the crown were hanging by their upper corners. When these splintered off, the whole fell down."

The preceding method of fracture also took place in several model arches of chalk, loaded for the purpose, and Dr. Robison explains the phenomena as follows. He supposes that the pressure from the crown is communicated in a straight line along as many voussoirs as one straight line will pass through. That is, he considers each of the four parts ED, DA, A B, BC, as one separate stone, not liable to be broken. The preliminary chipping from I, H, F, and G, he supposes to have arisen from the whole superincumbent pressure being there sustained at the corner of the arch-stones. When the arch opened underneath A, the whole pressure was supported at a and b, since the opening at B and D deprived the arch of the support at those points. This occasioned the chipping there observed just before the fall. We must, however, remark, that the loose manner in which the preceding account is given renders it impossible to say whether or no Dr. Robison was justified in supposing the line of communication of the pressure to be straight. His hypothesis might equally apply, if AHD were a convex curve, touching the intrados at H. This experiment should be repeated, with more attention to minute circumstances and actual measurement.

This very ingenious and probable explanation, which, supposing the slipping of individual voussoirs to be impossible, may be considered as almost unobjectionable, led its author to recommend that the arch should always be made so flat as to admit the same straight line being drawn so as to pass through some point of every voussoir on each side of the key-stone. That such an arch cannot be destroyed without either removing the pier, or crushing the material, is evident in the case of a triangular arch, slipping being supposed impossible, since there is no part of the arch which exerts any effort to overturn the rest, but

only to crush it. Blackfriars Bridge has arches of this kind, not indeed triangular, but so flat that a straight line can be drawn through all the voussoirs, in the manner recommended by Dr. Robison. M. Yvon de Villarceau has lately propounded a new theory of the resistance of arches, which perhaps it would be more satisfactory to discuss under the article BRIDGE. For general information upon the subject of arches the reader is, however, referred to Dr. Robison's work above cited; to Professor Moseley's Engineering and Architecture;' or to Gwilt's and Ware's Tracts on Vaults and Bridges. For the method of building an arch, see CENTERING, to which also we must defer the account of a method of constructing arches lately invented by Mr. Brunel, in which the stones are so joined that each half of the arch supports itself independently of the other.

ARCH, TRIUMPHAL, a structure which the Romans used to erect across their roads, or bridges, or at the entrance of their cities, in honour of victorious generals or emperors. They were of two kinds; temporary arches made of wood, on the occasion of a triumph, when the procession passed under the arch, and the conqueror had the triumphal crown placed on his head. These arches were removed after the ceremony. The others were permanent structures, built first of brick, afterwards of hewn stone, and lastly made of, or at least cased with marble. Their general form is that of a parallelopipedon, which has an opening in the longer side, and sometimes a smaller opening on each side of the large one. These openings are arched over with semicircular arches, and the fronts are decorated with columns and their accessories on lofty pedestals: the whole is surmounted by a heavy attic, on the faces of which inscriptions were generally placed.

Triumphal arches were erected under the republic. An arch of P. Cor. Scipio Africanus (Liv. xxxvii. 3), is mentioned as having been built on the Clivus Capitolinus. (See also Liv. xxxiii. 27, on the arches of L. Stertinius.) The Fabian arch is mentioned by Cicero (Pro Planco ') under the name of Fabianus fornix:' it stood by the Via Sacra, near the spot afterwards occupied by the temple of Antoninus and Faustina. It was raised in honour of Fabius, surnamed Allobrogus, from his victory over the Allobroges. This arch is also mentioned by Seneca, who calls it 'Fabianus arcus.' The term used by Dion Cassius for a triumphal arch is átis троraiópоpos. The arches

of Stertinius and Scipio were ornamented with gilded statues; and that of Scipio with two horses also. Whether they precisely resembled the later arches as to their columns, rilievos, and other accessory parts, we cannot say. As far as we can judge from medals, these early triumphal arches consisted of a single arch with a column on each side, without a stylobate; the arch was surmounted by a simple border as a kind of architrave. Under the emperors these monuments became very numerous, and were overcharged with ornaments. Drusus, the step-son of Augustus, is mentioned as the first who had one raised to him after death, and Livia, the wife of Augustus, was the first woman to whom a similar honour was decreed. Augustus himself had several triumphal arches erected to him, of which the one at Rimini, where the Flaminian Way terminated, still remains, and serves as a gate to the town on the side towards Rome. Another arch, also erected to Augustus, though inferior in beauty to that of Rimini, exists at Susa, at the commencement of the road which leads over Mont Genèvre into France. Of the

triumphal arches remaining at Rome, that of Titus is the oldest. It was erected to him after his death by the senate, in memory of his conquest of Judæa. This arch is ornamented with sculptures representing the triumph of the conqueror, and with the ornaments of the temple of Jerusalem which he brought as spoils to Rome. But arches were not erected solely to commemorate victories and conquests; they were also raised in honour of emperors for benefits conferred on their country on some particular occasions: such is the fine arch of Trajan, on the old mole of Ancona. It is of white marble, and chaste in its style; the inscription states that it was raised "by the senate and people of Rome to Trajan, Emperor and Cæsar, son of Nerva, the conqueror of the Germans and Dacians, high pontiff, &c., a most provident prince, for having at his own expense constructed the mole, and thus rendered the access to Italy on this side safer to navigators." Bronze statues of Trajan, of his wife Plotina, and his sister Marciana, were placed on the summit of the arch, but they have been destroyed. Another fine arch in memory of Trajan exists at Benevento; it is

ornamented with fine rilievos, and is in very good preservation. All these are single arches; but others have two smaller archways, one on each side of the great central one. These are consequently oblong in their shape, and have a heavier appearance than the single arch. Two of these triple arches still exist at Rome, that of Septimius Severus, and that called the arch of Constantine, which we have chosen for our illustration. The view here given is from an original drawing. The arch of Constantine is in the valley at the foot of the Palatine Hill, and near the Colosseum. It is the most complete of all the triumphal arches at Rome; that of Titus has only a central archway, and that of Septimius Severus is more dilapidated, and more encumbered by accumulations of soil. The style of Constantine's arch is also, for the most part, superior to that of the age in which it was executed, as it consists, in great measure, of the materials of a similar monument which had been erected to Trajan. But at the same time, owing to its being chiefly built of old materials, and owing to want of skill in the architect and sculptor, it presents some striking discrepancies of parts, and some specimens of bad taste. The captive Parthians, and other sculptures, which were historically appropriate on the arch of Trajan, are here employed to decorate that of Constantine. Our view indicates an excavation, bounded by a wall of an elliptical form, within which the monument stands. Accumulations of soil had raised the level of the ground nearly up to the bases of the columns; the excavation was

made for the purpose of clearing away the rubbish, and the wall with the view of protecting the monument.

The number of marble arches, in honour of emperors and other personages, existing in ancient Rome alone, is stated to have been at one time thirty-six: only five or six are now remaining. Other arches are found in various parts of Italy, at Aquino, Aosta, Pola in Istria, &c.; several in the south of France, of which those of Nîmes and Orange are the best preserved; several in Macedonia, Athens, and in other parts of Greece, all however belonging to the Roman period: several in Syria, and in Barbary, particularly one at Tripoli; and another at Constantina, described by Shaw. In modern times, triumphal arches have been raised in imitation of the Roman ones. Those of the gate St. Denis and the gate St. Martin at Paris were raised in honour of Louis XIV. Bonaparte also had one constructed on the Place du Carousel; it is a triple arch, and has all the heaviness of that particular species of structure. Another, and a much finer one, was begun by his order at Milan, on the opening of the famous road across the Simplon. It was interrupted by the overthrow of the French empire, but has since been completed by order of the Austrian government, under the appellation of the Arch of Peace. In London, two structures of the same kind have been raised of late years, a single arch at Hyde Park Corner, and a triple one of marble originally erected in front of Buckingham palace, but removed on the

erection of a new front to that building, to the north-eastern entrance of Hyde Park. On Roman triumphal arches the reader may consult Pitiscus, 'Lexicon Antiquitatum Romanorum,' art. Arcus.

The arch of Augustus at Rimini is 60 feet in height and 27 in depth or thickness; the gateway is 31 feet, being the widest opening among all the ancient arches in Italy. The front is decorated with two Corinthian columns 32 feet high. It is made of Istrian marble. The arch of Septimius Severus is 61 feet high, 71 feet long, and 22 feet deep. The central archway is 36 feet high, and 22 feet wide. The side arches are 22 feet high and 10 wide.

The arch of Orange, in the south of France, supposed, but upon no certain grounds, to have been erected in honour of Caius Marius, is 70 feet high and 66 long. It is a triple arch.

Arches bearing a great resemblance to triumphal arches, but simpler in form and less ornamented, were also erected at the entrances to the road-way of bridges in Italy, Spain, and France; though comparatively few of them remain. There is one on the bridge erected by Trajan at Alcantara in Spain. Two of very elegant form and in good preservation occur at the bridge of St. Chamas in Provence; and there is a similar double-arch bridge at Saintes in the South of France. These bridge-arches all bear inscriptions recording the date, &c., of their erection. ARCHEOLOGY, literally 'the study of antiquity or ancient things,' from apxaîos, ancient, and λóyos, a discourse. Though the term is often used, its meaning in this country has not always been very exactly fixed; but there is nothing properly belonging to it which is not included under the heads of ANTIQUITY and ANTIQUITIES. Like the latter term, the term archæology has been somewhat capriciously confined to the study of Greek and Roman art; but it is now usually employed to express generally the study of all that concerns the early history of any civilised nation or country. The great extension which the study of archæology has received of late years, and is still receiving, has led to the formation of various associations, both in this country and throughout Europe, in order to unite the exertions of all who devote themselves to the study. One of the first of these was the Archæological Institute of Rome, founded in 1829. In our own country, not only are there metropolitan institutes, which have for their object the investigation of the antiquities of the country generally, but in several counties associations have been established, having for their special object the study and preservation of local antiquities.

ARCHBISHOP. For what belongs to the episcopal character and office generally, we refer to the word BISHOP: we mean to confine ourselves in this article to what belongs more peculiarly to the archbishop. For though, in this country, and generally throughout Europe, the archbishop has his own diocese in which he exercises ordinary episcopal functions like any other bishop in his diocese, yet he has a distinct character, having an admitted superiority and a certain jurisdiction over the bishops in his province, who are sometimes called his suffragans, together with some peculiar privileges. This superiority is indicated in the name. The word or syllable arch is the Greek element apx (which occurs in apxǹ, àpxòs, apxwu, &c.), and denotes precedence or authority. It is used extensively throughout ecclesiastical nomenclature, as may be seen in Du Cange's Glossary,' where there are the names of many ecclesiastical officers into whose designations this word enters, who were either never introduced into the English Church or have long ceased to exist. Exalted officers of state have sometimes designations into which this word enters, as arch-duke. Why this word was used peculiarly in ecclesiastical affairs rather than any other term denoting superiority is probably to be explained by the fact that the term dpxiepeùs, for chief-priest, occurs in the Greek text of the Christian Scriptures. Patriarch is a less obvious compound of the same class, denoting the chief father, and is used in ecclesiastical nomenclature to denote a bishop who has authority not only over other bishops, but over the whole collected bishops of divers kingdoms or states; it is analogous in signification to the word pope (papa), a bishop to whom this extended superintendence is attributed.

Whatever might be the precise functions of the episcopus (éríσкоTOя, bishop), the term itself occurs in the writings of St. Paul, Phil. i. 1, 1 Tim. iii. 2, and elsewhere; but the word dpxenioкоTоs, or archbishop, is not found till about or after the 4th century. Cyrillus Archiepis copus Hierosolymitanorum, and Celestinus Archiepiscopus Romanorum, occur under these designations in the proceedings of the Council held at Ephesus, A.D. 431. Other terms by which an archbishop is sometimes designated are primate and metropolitan. The first of these is formed from the Latin word primus, 'the first,' and denotes simple precedency, the first among the bishops. The latter is a Greek term, which rendered literally into English would be the man of the mothercity, that is, the bishop who resides in that city where is the mother church of all the other churches within the province or district in which he is the metropolitan.

The term metropolitan, when thus analysed, points out to us the origin of whatever real distinction there is between bishop and archbishop, or, in other words, the cause of that elevation which is given to the archbishop above the bishops in his province, when it is not to be attributed to mere personal assumption, or to be regarded only as an unmeaning title. The way in which Christianity became extended over Europe was this: an establishment was gained by some zealous preacher in some one city; there he built a church, performed in it the

rites of Christianity, and lived surrounded by a company of clerks engaged in the same design and moving according to his directions. From this central point, these persons were sent from time to time into the country around for the purpose of promoting the reception of Christianity, and thus other churches became founded, offspring or children, to use a very natural figure, of the church whence the missionaries were sent forth. When one of these subordinate missionaries had gained an establishment in one of the more considerable cities, remote from the city in which the original church was seated, there was a convenience in conferring upon him the functions of a bishop; and the leading design, the extension of Christianity, was more effectually answered than by reserving all the episcopal powers in the hands of the person who presided in the mother church. Thus other centres became fixed; other bishoprics established; and as the prelate who presided in the first of these churches was still one to whom precedence at least was due, and who still retained in his hands some superintendence over the newer bishops, archbishop became a suitable designation. Thus, in England, when there was that new beginning of Christianity in the time of Pope Gregory, Augustine, the chief person of the mission, gained an early establishment at Canterbury, the capital of the kingdom of Kent, through the favour of King Ethelbert. There, in this second conversion, as it may be called, the first Christian church was established, and thence the persons were sent out who at length Christianised the whole of the southern part of England. Paulinus, in like manner, a few years later, gained a similar establishment in the kingdom of Northumbria, through the zeal of King Edwin, who received Christianity, and built him a church at York, one of his royal cities, which may be regarded as the chief city of Edwin's kingdom. From York the light of Christianity was diffused over the northern parts of England, as from Canterbury over the southern. It seems to have been the peculiar diligence and dignity of Paulinus which procured for him the title of archbishop, and gave him a province, instead of a diocese only, as was the case with the other members of the Augustinian mission. This was done by special act, under the authority, it is said, of Justus, an early successor of Augustine. But the precedence of the real English metropolitan is acknowledged in two circumstances: in the style, the one being a primate of England, and the other the primate of all England; and in the rank, precedence being always given to the Archbishop of Canterbury, and the Lord Chancellor of England being interposed in processions between the two archbishops. Under the later empire the name metropolis was applied to various cities of Asia and conferred on them as a title of rank. The emperors Theodosius and Valentinian conferred on Berytus in Phoenicia the name and rank of a metropolis "for many and sufficient reasons." ('Cod.' xi. tit. 22 (21).) Accordingly the bishop of a metropolis was called metropolitan (unтporoλirns), and the bishop of a city which was under a metropolis was simply called bishop. All the bishops, both metropolitan and others, were subject to the archbishop and patriarch of Constantinople, who received his instructions in ecclesiastical matters from the emperor. ('Cod.' i. tit. 3, s. 42, 43.)

The precise amount of superintendence and control preserved by the archbishops over the bishops in their respective provinces, does not seem to be very accurately defined. Yet if any bishop introduces irregularities into his diocese, or is guilty of scandalous immoralities, the archbishop of the province may, as it seems, inquire, call to account, and punish. He may, it is said, deprive. In 1822 the archbishop of Armagh deposed the bishop of Clogher from his bishopric. In disputes between a diocesan and his clergy an appeal lies to the archbishop of the province in all cases except disputes respecting curates' stipends. (1 & 2 Vict. c. 106.) Rolle, a good authority, says that the archbishop may appoint a co-adjutor to one of his suffragans who is infirm or incapable. This right is now confirmed by 6 & 7 Vict. c. 62, intituled 'An Act to provide for the Performance of the Episcopal Functions in case of the Incapacity of any Bishop or Archbishop.'

An archbishop has a right to name one of his clerks or chaplains to be provided for by every bishop whom he consecrates. The present practice is for the bishop whom he consecrates, to make over by deed to the archbishop, his executors and assigns, the next presentation of such benefice or dignity which is at the bishop's disposal within his see, as the archbishop may choose. This deed only binds the bishop who grants, and, therefore, if a bishop dies before the option is vacant, the archbishop must make a new option when he consecrates a new bishop. If the archbishop dies before the benefice or dignity is vacant, the next presentation goes to his executors or assigns according to the terms of the grant.

The archbishop also nominates to the benefices or dignities which are at the disposal of the bishops in his province, if not filled up within six months from the time of the avoidance. During the vacancy of a see, he is the guardian of the spiritualities.

Certain of the bishops are nominally officers in the Cathedral of Canterbury, or in the household of the archbishop. The archbishop has also certain honorary distinctions; he has in his style the phrase "by Divine providence," but the bishop's style runs "by Divine permission;" and while the bishop is only installed, the archbishop is enthroned.

The archbishops may nominate eight clerks each to be their chap. lains. The archbishop of Canterbury claims the right of placing the crown upon the head of a king at his coronation; and the archbishop of York claims to perform the same office for the queen consort. The