&

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54

16

Capital 30 Min. Architrave 311⁄2 Min. Friezer3te Minutos

10

7'

to

Whole hight of the Entablature 1. Module 441⁄2 Minutes

22

10

The

TUSCAN ORDER

A.Bell Soulp?

Principles. have been justly blamed, as it is neither natural, reafonable, nor beautiful.

36

Vignola's method.

Monfieur Auzoult obferves, that a column, fuppofing its shafts to be the fruftum of a cone, may have an additional thickness in the middle, without being fwelled there beyond the bulk of its inferior parts; and fuppofes the addition mentioned by Vitruvius to fignify nothing but the increase towards the middle of the column, occafioned by changing the ftraight line, which at firft was in ufe, for a

curve.

This fuppofition is extremely juft, and founded on what is obferved in the works of antiquity; where there is no inftance of columns thicker in the middle than at the bottom, though all have the fwelling hint ed at by Vitruvius, all of them being terminated by curves; fome granite columns excepted, which are bounded by ftraight lines; a proof, perhaps, of their antiquity, or of their having been wrought in the quarries of Egypt by bungling and unfkilful work

men.

Monfieur Blondel, in his book entitled Refolution des quatre principaux problemes d' Architecture, teaches various manners of diminishing columns; the best and fimpleft of which is by means of the inftrument which Nicomedes invented to defcribe the first conchoid: for this, being applied at the bottom of the fhaft, performs at one fweep both the fwelling and the diminution; giving fuch a graceful form to the column, that it is univerfally allowed to be the most perfect practice hitherto difcovered. The columns in the Pantheon, accounted the most beautiful among the antiques, are made in this manner; as appears by the exact measures of one of them to be found in Defgodet's antiquities of Rome.

To give an accurate idea of the operation, it will be neceffary first to describe Vignola's method of diminution, on which it is grounded. "As to this second method, fays Vignola, it is a difcovery of my own; and although it be lefs known than the forit will be easily comprehended by the figure. Having therefore determined the measures of your. PL. XXXIV. column, (that is to fay, the height of the fhaft, and its inferior and fuperior diameters), draw a line indefinitely from C through D, perpendicular to the axis of the column: this done, fet off the distance CD, which is the inferior femi-diameter, from A, the extreme point of the fuperior femi-diameter, to B, a point in the axis; then from A, through B, draw the line A B E, which will cut the indefinite line C D in E; and, from this point of interfection E, draw thro' the axis of the column any number of rays as E b a, on each of which, from the axis to wards the circumference, fetting off the interval C D, you may find any number of points, a, a, a, through which if a curve be drawn, it will defcribe the fwelling and diminution of the column."

40

Nicome

ment.

Though this method be fufficiently accurate for des's inftru- practice, efpecially if a confiderable number of points be found, yet, ftrictly speaking, it is defective; as the curve muft either be drawn by hand, or by applying a flexible ruler to all the points; both of which are liable to variations. Blondel therefore, to obviate this objection, (after having proved the curve paffing from A to C through the points a a, to be of the fame na

ture with the first conchoid of the ancients), employed Principles. the inftrument of Nicomedes to defcribe it; the conftruction of which is as follows:

Having determined, as above, the length of the fhaft, with the inferior and fuperior diameters of the column, and having likewife found the length of the line C D E, take three rulers, either of wood or metal, as FG, ID, and AH; of which let F G and ID be faftened together at right angles in G. Cut a dove tail groove in the middle of FG, from top to bottom; and at the point E on the ruler ID (whofe distance, from the middle of the groove in F G, is the fame as that of the point of interfection from the axis of the column) fix a pin; then on the ruler A H fet off the distance A B, equal to C D the inferior semidiameter of the column, and at the point B fix a button, whofe head must be exactly fitted to the groove made in FG, in which it is to flide; and, at the other extremity of the ruler A H, cut a flit or canal from H to K, whofe length must not be lefs than the difference of length between E B and E D, and whofe breadth must be fufficient to admit the pin fixed at E, which muft pafs through the flit, that the ruler may flide thereon.

The inftrument being thus completed, if the middle of the groove, in the ruler FG, be placed exactly over the axis of the column, it is evident that the ruler A H, in moving along the groove, will with the extremity A defcribe the curve A a a C; which curve is the fame as that produced by Vignola's method of diminution, fuppofing it done with the utmost accuracy; for the interval A B, a b, is always the fame; and the point E is the origin of an infinity of lines, of which the parts B A, ba, ba, extending from the axis to the circumference, are equal to each other and to DC. And if the rulers be of an indefinite fize, and the pins at E and B be made to move along their respective rulers, fo that the intervals A B and DE may be augmented or diminished at pleasure, it is likewife evident that the fame instrument may be thus applied to columns of any fize.

41

diminution.

In the remains of antiquity the quantity of the di- Quantity of minution is various; but feldom lefs than one eighth of the inferior diameter of the column, nor more than one fixth of it. The last of these is by Vitruvius esteemed the moft perfect.

Of the TUSCAN Order.

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This is the moft folid and fimple of all the orders. Pl. XXXV. It is compofed of few parts, devoid of ornaments, and fo maly, that it feems capable of fupporting the heaviest burden. There are no remains of a regular Tuscan order among the antiques: the doctrine of Vitruvius concerning it is obfcure; and the profiles of Palladio, Scamozzi, Serlio, de l'Orme, and Vignola, are all imperfect.

The height of the Tufcan column is 14 modules, or femi-diameters, each confifting of 30 minutes; and that of the whole entablature 3 modules; which being divided into 10 equal parts, three of them are for the height of the architrave, three for the frize, and the remaining four for the cornice: The capital is one module; the bafe, including the lower cincture of G g 2

the

Principles the fhaft, is likewife one module; and the shaft, with its upper cincture and aftragal, 12 modules. These are the general dimensions of the order; the particular dimenfions may be learned by inspection of the plates.

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Plate XXXVI.

In the remains of antiquity, the quantity of diminution at the top of the Tufcan column is various; but feldom less than one eighth, nor more than one fixth, of the inferior diameter of the column. The laft of these is generally preferred; and Chalmers and others make the fame diminution in all columns, without regard to their order.

Of the DORIC Order.

This order is next in ftrength to the Tufcan; and, being of a grave, robuft, and mafculine afpect, is by Scamozzi called the Herculean. As it is the most ancient of all the orders, it retains more of the ftructure of the primitive huts than any of the reft; the triglyphs in its frize reprefenting the ends of the joifts, and the mutules in its cornice representing the rafters.

The height of the Doric column, including its capital and bafe, is 16 modules, and the height of the entablature four; the latter of which being divided into eight parts, two of them are for the architrave, three for the frize, and three for the cornice.

In most of the antiques, the Doric column is executed without a base. Vitruvius likewife makes it without one; the bafe, according to him, having been first employed in the Ionic order, in imitation of the fandal of a woman's foot. Scamozzi blames this practice, and most of the modern architects are of his opinion.

44 Ornaments In the profile of the theatre of Marcellus, the of the frize. frize is enriched with husks and roses; the architrave confifts only of one fafcia and a fillet; the drops are conical; the metope is enriched with a bull's fkull, adorned with a garland of beads, in imitation of thofe on the temple of Jupiter Tonans, at the foot of the Capitol. In fome antique fragments, and in a great many modern buildings, the metopes are alternately adorned with ox-fkulls and pateras. But they may be filled with any other ornaments, according to the deftination of the building.

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Plate XXXVII.

The IONIC Order

Is of a more flender make than the Dorie or Tufcan; its appearance is fimple, yet graceful and majeftic; its ornaments are few; fo that it has been compared to a fedate matron, in decent, rather than magnificent, attire.

Among the ancients, the form of the Ionic profile appears to have been more pofitively determined than that of any other order; for, in all the antiques at Rome (the temple of Concord excepted), it is exactly the fame.

The modern artists have likewife been unanimous in their opinions; all of them, excepting Palladio and his imitators, having employed the dentil, cornice, and the other parts of the profile, nearly as they are found in the Collifeum, the temple of Fortune, and the theatre of Marcellus.

The height of the Ionic column is 18 modules, Principles. and that of the entablature 41, or one quarter of the height of the column, as in the other orders, which is a trifle lefs than in any of the antique Ionics. In all the antiques, the bafe is Attic; and the fhaft of the column may either be plain, or fluted with 24 flutings, or 20 only, as in the temple of Fortune. The plan of the flutings may be a trifle more than a femicircle, as in the forum of Nerva, because they then appear more distinct. The fillets, or intervals between them, must not be broader than one third of the breadth of a fluting, nor narrower than one fourth. The ornaments of the capital must correspond with the flutings of the fhaft; and there must be an ove above the middle of each fluting. The volutes ought to be traced according to Mr Goldman's method, which is as follows:

46

Plate XXXVIII. fig. 9. Draw the cathetus F C, Method of whofe length must be 15 minutes, or one fourth of a drawing module; and, from the point C, defcribe the eye of volutes. the volute A E B D, of which the diameter is to be 63 minutes; divide it into four equal fectors by the diameters A B, D E. Bifect the radii C A, C B, in 1 and 4; and on the line 1, 4, conftruct a fquare 1, 2, 3, 4. From the centre C, to the angles 2, 3, draw the diagonals C 2, C 3, and divide the fide of the fquare 1, 4, into 6 equal parts, at 5, 9, C, 12, 8. Then through the points 5, 9, 12, 8, draw the lines. 5, 6, 9, 10, 12, 11, 8, 7, parallel to the diameter E D, which will cut the diagonals in 6, 7, 10, 11; and the points 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, will be the centres of the volute. From the firft centre I, with the diftance 1 F, defcribe the quadrant F G ;from the second centre 2, with the distance 2 G, defcribe the quadrant GH; and, continuing the fame operation from all the 12 centres, the contour of the volute will be completed.

Fig. 10. The centres for defcribing the fillet are found in this manner. Construct a triangle, of which the fide A F is equal to the part of the cathetus contained between AF and the fide F V, equal to C 1 ; place the diftance FS from F towards A, equal to FS the breadth of the fillet, and through the point. S draw the line S T, which will be to C in the fame proportion as A S is to A F; place this line on the diameter of the eye A B; divide it into three equal. parts; and, through the points of divifion, draw lines. parallel to the diameter E D, which will cut the diagonals C 2, C3, and you will have twelve new centres, from whence the interior contour of the fillet may be described, in the fame manner as the exterior one was from the first centres.