Abacus (architecture)

“ In the Greek Corinthian order the abacus is moulded, its sides are concave and its angles canted (except in one or two exceptional Greek capitals,
Fig. 1.—Roman Abacus. where it is brought to a sharp angle) ; and the same shape is adopted in the Roman and Renaissance Corinthian and Composite capitals, in some cases with the ovolo moulding carved.In Romanesque architecture the abacus is square with the lower edge splayed off and moulded or carved, and the same was retained in France during the medieval period ”

“ In this country, in fact, the form of the abacus is the distinguishing feature between the transition to the perfected style, while in France there is no such distinction to be found. The difference is more one of feeling, which the practical eye perceives at once without being able to define.
Though I speak of the Early Pointed as a newly-generated art—as it in effect was—it must never be forgotten that it is a distinct and natural growth from the pre-existing Romanesque. The more I study old examples the more obvious does this appear. ”

“ Even this, the overhanging of the entablature, would be not a little offensive to the eye, were the abacus no larger than the architrave is deep; whereas, being larger, it projects forwarder than the face of the architrave, thereby producing a powerful degree of one species of æsthetic effect, namely, contrast,—and if contrast, of course variety also; for though there may be variety without contrast, there cannot be contrast without variety. ”

“ Abacus.—The plate or shallow block forming the uppermost member of a capital is so called for the sake of distinction, for when a similar one is placed beneath the base of a column, it is called a plinth. The Doric abacus is spoken of at page 14, and is here shown in a plan of the capital and architrave; a a a a being the angles of the soffit or underside of the abacus which overhang the echinus e e e e ”

“ The unsymmetrical plan of the impost (Fig. 31) , where one of the lateral vaulting shafts advances forward of the other, is caused by the thickening of the arcade spandrel on that side in order to reinforce the great piers of the western tower. The adjustment of this compound abacus to its load could hardly be improved; there is even less unoccupied space here than in the square abacus of the choir already noticed. ”

“ In our own earliest style, and in the French examples down to a far later date, there is one feature which I confess I have a great love for—I mean the square and angular abacus. I think it is probably the feeling for this feature which has, more than any other, led to our tendency to follow French types. I would mention, however, that it is not necessarily a foreign feature, as it is found in our own earlier style, and sometimes (as in the side chapels of the nave at Chichester) is continued later ”

“ A peculiarity of the architecture consists in the high abacus--a frustum of an inverted pyramid--which is interposed between the capital of the column and the arch that springs from it, as if to give greater height than the columns alone would afford. ”

“ Above the echinus, which is circular, like the shaft, comes the highest member—the abacus, a square stout slab of marble, which completes the capital of the column. The [95] whole is most skilfully designed to convey the idea of sturdy support, and yet to clothe the support with grace. The strong proportions of the shaft, the slight curve of its outline, the lines traced upon its surface by the channels, and even the vigorous uncompromising planting of it on the square step from which it springs, all contribute to make the column look strong. ”

“ She is not to imitate directly the natural arrangement; she is not to carve irregular stems of ivy up her columns to account for the leaves at the top, but she is nevertheless to place her most exuberant vegetable ornament just where Nature would have placed it, and to give some indication of that radical and connected structure which Nature would have given it. Thus the Corinthian capital is beautiful, because it expands under the abacus just as Nature would have expanded it ”

“ At least that method, and the other one of turning the volutes diagonally, are the only methods that have been practised for giving perfect regularity to the Ionic capital by means of four equal faces; for, though difficult, it is possible to accomplish the same purpose differently, by making the abacus quite square, as in the Doric Order, and letting the volutes grow out of it on each side or face, their curvature commencing not on the upper horizontal edge, but descending from the vertical edges of the abacus. ”

“ Thus, in the design of the temple the lines will be adjusted with due regard to the diminution.
5. The shafts of the columns having been erected, the rule for the capitals will be as follows. If they are to be cushion-shaped, they should be so proportioned that the abacus is in length and breadth equivalent to the thickness of the shaft at its bottom plus one eighteenth thereof, and the height of the capital, including the volutes, one half of that amount. The faces of the volutes must recede from the edge of the abacus inwards by one and a half eighteenths of that same amount. ”

“ This rope-moulding is repeated on all the ridge ribs, and in each it is tied in a knot half-way along, a knot which is so much admired that the whole vault is called 'a abobada dos nós' or vault of the knots.
The capitals are more curious than beautiful; the lower have clumsy, early-looking foliage and a large and curious abacus. First each capital has a square abacus of some depth, then comes a large flat circle, one for each three caps, and at the top a star-shaped moulding of hollow curves, the points projecting beyond the middle of the square abaci below. The higher capitals are better. ”

“ The windows are wide in proportion to their height, and are covered in with round arches.
In the interior (Fig. 18) the Norman piers consist of simple cylindrical columns of great size, frequently carved with large zig-zags or spiral lines carried round them, and finished with bold caps and bases. The most frequent caps are of the “cushion” form, which resembles one or more spherical figures having portions cut off perpendicularly. The caps are also sometimes carved with human or other figures. The abacus is always solid, and generally square in shape. ”

“ Tuscan Order of Architecture. The simplest of the five Orders of classical architecture, having no ornament whatever; unknown to the Greeks; a variety of Roman Doric (q.v.) . The column is about seven diameters high, including the base and capital. The base is half a diameter in height; the capital is of equal height, having a square abacus, with a small projecting fillet on the upper edge—under the abacus is an ovolo and a fillet with neck below; the shaft is never fluted; the entablature is quite plain, having neither mutules nor modillions; the frieze also is quite plain. ”

“ At the same time the whole church, including these two bays, was vaulted with quadripartite vaults having transverse and diagonal ribs, but no longitudinal ribs, which last are usually wanting in the early pointed vaults of England. These ribs interpenetrate at their springing, and thus are gathered upon a single round abacus which covers a triple group of capitals. They receive no support from the lower piers, but their triple vaulting shafts, which are slender and closely grouped, are sustained by corbels placed just above the capitals of the lower piers. ”

“ The columns are surmounted by a small square slab, technically called an abacus, and heavy square beams or architraves span the spaces between the columns, while the roof between the architraves has a slightly segmental form. The tombs of the later period, viz. of the eighteenth and nineteenth dynasties, are very different from those of [23] the twelfth dynasty, and present few features of architectural interest, though they are remarkable for their vast extent and the variety of form of their various chambers and galleries. ”

“ The groining ribs are very bold, and well moulded. There is no triforium, and the clerestory windows come down to a string-course just above the points of the main arches. They are of two lights, with a circle in the arched head, and their rear arches are moulded and carried on engaged jamb-shafts. The transepts have rose-windows in the bays next the choir, and lancet-windows in the north and south bays, and the carved abacus is carried over these as a label. There seem to have been rose windows round the principal apse at a lower level than the other clerestory windows ”

“ Arches pointed, generally lancet; often richly moulded. Triforium arches and arcades open with trefoiled heads. Piers slender, composed of a central circular shaft surrounded by several smaller ones, almost or quite detached; generally with horizontal bands. In small buildings plain polygonal and circular piers are used. Capitals concave in outline, moulded, or carved with conventional foliage delicately executed and arranged vertically. The abacus always undercut. ”

“ The voussoirs of the arch are not all of equal size in each order, and on one member the chevrons are reversed on opposite sides of the centre stone except for one accidental intermission. The abacus, nearly six inches deep, has a flat upper part on which a continuous diaper of Greek crosses has been cut. ”

“ To the 13th century mainly, the abacuses are more or less thick, and their profiles are more or less complicated, according to whether the capitals are placed more or less close to the ground. In the high parts of the buildings, the abacuses are very-thick, largely shaped, while in the low parts they thinner and are finely profiled. ”

“ LXVII. The spur itself is carved into a curling tendril or concave leaf, which supports the projecting angle of a four-sided abacus, whose hollow sides fall back behind the bell, and have generally a rosette or other ornament in their centres. The mediæval architects often put another square abacus above all, as represented by the shaded portion of Fig. LXVII., and some massy conditions of this form, elaborately ornamented, are very beautiful ”

“ The abacus in Norman work is square where the columns are small; but on larger piers it is sometimes octagonal, as at Waltham Abbey. The square of the abacus is often sculptured, as at the White Tower and at Alton (fig. 2) . In early English work the abacus is generally circular, and in larger work a continuation of circles (fig. 4) , sometimes octagonal, and occasionally square. The mouldings are generally rounds, which overhang deep hollows. The abacus in early French work is generally square, as at Blois (fig. 3) . ”

“ Caption: "Roman Abacus or Calculating Table."] The Roman abacus (figured here from the Kircherian Museum at Rome) was on the same system. It is divided into eight lower and eight higher (somewhat shorter) groves: there is [p. 3] also a ninth lower groove, without an upper groove to correspond. Four sliding buttons are attached to each lower groove except the eighth, which has five: each upper groove has one button. ”

“ The capitals of the columns in the jambs are all sculptured with subjects in a very exquisite fashion. There is here no grotesqueness or intentional awkwardness, but extreme beauty of design, simplicity of story, and fitness for the position chosen. The abaci are carved throughout with conventional foliage, well arranged and delicately cut. I know little even of French carving of the thirteenth century which surpasses this beautiful work, and none anywhere which more entirely deserves our admiration, or which may more worthily kindle our emulation. ”

“ Peter's, an attic is interposed, but to spring a vault from an attic wall is an architectural barbarism; though it is perhaps no greater one than to spring it from an entablature, as the architects of the Renaissance had done from Brunelleschi down. In the small order of the aisles the entablature is simplified, and has only an architrave and cornice; while a member, like a diminutive attic, in retreat of the cornice, is interposed at the impost. ”

“ The principal member of the capital, 2 feet 10 inches in height, is bell-shaped in the Persepolitan style, and is surmounted by an oblong abacus 12 inches high, which serves as a pedestal for a lion seated on its haunehes, and 4 1/2 feet in height. Two or three mouldings are inserted between the shaft and the bell capital, and one intervenes between the latter and the abacus. The total height above the level of the Water is 44 feet 2 inches. Including the submerged portion the length of the monument cannot be less than 50 feet, and its weight is estimated to be 50 tons [12] . ”

“ The vaulting-shafts run upward between each bay in groups of three. The abacus from which the groining-ribs apparently spring, is partly a continuation of the stringcourse at the base of the clerestory, and is gracefully trefoiled.
The whole work on the north side of the nave is bolder and more effective than that on the south. We have no record of the construction of this side, but from its strong Perpendicular character it can hardly be earlier than 1360. The clustered pier-shafts have much smaller capitals of leafage than those opposite, and the leafage does not pass round continuously. ”

“ The nave has six bays, with five antique columns on each side, of cipollino, granite, white and black, and white-veined marble. The caps are very varied. Some are Byzantine of the type of those at S. Apollinare in Classe; two are truncated reversed pyramids with roughly cut scrolls on the surface, and one of these has a super-abacus. Two of them are queer, rough things, with brackets at the angles in place of volutes, and a deep abacus sloping back, with a cross upon it. The bases of the pillars are boxed in, as at the cathedral. An antique base serves as support to the holy-water basin. ”