CIVIL ARCHITECTURE. 



611 



Oi<lrs up- 

 on orders. 



practice. middle of the abacus, and would pass over the faces of 

 -<'- * the spirals or volutes of the capitals of the pilasters. 



Orders upon orders. -In placing one order above ano- 

 ther, we shall be naturally led, by the known laws of 

 gravity, to give the strongest and heaviest the lower 

 place, and the weakest and lightest the upper. Symme- 

 try and strength will also direct us to keep all their axis 

 in the same vertical line. 



In columns of equal diameters, the altitudes increase 

 from the Tuscan, by the gradations of the Doric and 

 Ionic to the Corinthian. In this progression, we per- 

 ceive that the Tuscan is stronger than the Doric, the 

 Doric than the Ionic, and the Ionic than the Corinthian ; 

 consequently, if the Doric be the lowest order, the suc- 

 ceeding one must be the Ionic ; if a third be added, it 

 must be the Corinthian. 



Vitruvius, book v. chap. vii. directs the height of the 

 columns of the superior order, to be a fourth less than 

 those of the inferior ; but Scammozzi's rule, which 

 is esteemed the best, is, that the lower diameter of the 

 superior column should be equal to the upper diameter of 

 the inferior, so that the different shafts bear the appear- 

 ance of one long tapering tree cut into so many pieces ; a 

 disposition appropriately corresponding to the origin of 

 columns. 



According to the rule of Vitruvius, if an Ionic co- 

 lumn of nine diameters were to be raised upon a Roman 

 Doric of eight, the* lower diameter of the Ionic would be 

 two-thirds of that of the Doric, which is a much less 

 quantity than is to be found in any ancient or modern 

 example of the diminution of the Doric shaft. 



In insulated columns, when the diminution of the su- 

 perior order is very considerable, the intercolumn be- 

 comes so wide, and the entablature so small and weak, 

 as to be in danger of breaking, which defect must be still 

 increased, if a third range be added : whence we may 

 again infer, that the theory of Scammozzi is preferable 

 to that of Vitruvius. 



For the sake of example, we shall suppose the stronger 

 order to be made the superior, as the Doric on the Ionic. 

 Here let the shaft of the Doric diminish five sixths of its 

 lower diameter, and its height will be but six diameters 

 and two-thirds of the Ionic below, which would make a 

 complete attic of the Doric, and render the application 

 of the orders in this inverted manner useless, as they 

 could not be made to accommodate the stories of the 

 building, neither would the upper ranges support their 

 own entablature. 



When the front of a building is to have two or more 

 orders in the altitude, the succession must be complete, 

 or the symmetry will be destroyed by the abrupt con- 

 trast of 'the parts. In attached columns, the superior 

 order may be permitted to recede, without danger eitlxr 

 of greatly offending the eye, or of impairing the strength 

 of the structure, as may be seen in the theatre of Mar- 

 ccllu ccUu8 ' ( Sce P |atc CLXX XVI. ) But when the stories 

 AT , ' of orders are insulated, the axis of the superior and infe- 

 rior columns must be kept in the same vertical lines. 



In cases where the upper order only consists in the cen- 

 tre of that below, in two equidistant parts from the mid- 

 dle, the portions of the entablature of the lower order, 

 in which there is no superior on!er, are generally finish- 

 ed with a balustrade, level with the fills of the windows. 

 \\e have but few examples in England, of more than 

 two ranges of columns in the game front. Indeed, when 

 there STL- three, it is difficult to preserve the character of 

 each, without some striking inconsistencies and defects 

 in the iiitcrcolumniations. 



The first and second orders should stand on plinths, 



Sumplr. 



I'l.XXXVI. 



as likewise the third, when there is one $ the point of Practice^ 

 view regulating those of the upper stories. In this case. s "V" 

 pedestals should be omitted in the upper orders ; but it 

 there be one, or a balustrade under the windows, the 

 base and Cornice should have but a small projection, and 

 be continued to profile upon the sides of the columns. 



When stories of arcades are raised one upon another, 

 and the piers decorated with orders, the inferior columns 

 should stand on plinths, and those of the upper stories 

 on pedestals, that the arches may receive a due propor- 

 tion. 



In some cases, instead of employing several orders 

 one above another, the ground floor of a building is made 

 in the form of a basement, on which is placed the order 

 by which the principal story is decorated. 



In Plate CLXXXVI. examples will be found of or- PLATE 

 ders upon orders, with and without arcades and pedes- CLXXXVI. 

 tals. They are taken from the inside of the temple of 

 Paestum, the outside of the Coliseum, the theatre of 

 Marcellus at Rome, and Whitehall in London. 



Arcades. When an aperture in a wall is too wide to Arcade?, 

 be lintelled, it is arched over, and receives the appellation 

 of an arcade, which term, in the plural number, indicates 

 a continued range of such apertures. They are not so 

 magnificent as colonnades, but are stronger, more solid, 

 and less expensive. 



In the construction of arcades, the piers require the 

 utmost care, to have them of sufficient strength to resist 

 the pressure of trie arches, particularly those at the ex- 

 tremities. In large arches, the key-stones should never 

 be omitted, and they should be carried to the soffit of 

 the architrave, where they will be useful in supporting 

 the centre of the entablature, v'hich would otherwise 

 have too great a bearing. The altitude of arcades should 

 never be much more nor much less than double their 

 breadth. The breadth of the pier should seldom exceed 

 two-thirds, nor be less than one-third of that of the ar- 

 cade ; and the angular one should have the addition of a 

 third, or even one half more than the re?t, according to 

 the nature of the design. The impost should not be less 

 than a ninth, nor more than a seventh of the breadth of 

 the arch ; and the archivolt not less than a tenth, nor 

 more than an eighth of the same breadth. The bottom 

 of the key-stone should be equal in breadth to that of 

 the archivolt ; and its length not less than one and a half, 

 nor more than double its bottom breadth." In groined 

 porticos, the thickness of the piers depend on the width 

 of the portico and the superincumbent buildings. It 

 should not, however, where beauty and symmetry are 

 consulted, exceed one-third, nor be less than one-fourth 

 of the breadth of the arcade. 



When the arcades form blank recesses, with the backi 

 pierced for doors, or windows, or recessed with niches, 

 the recesses should be at least sufficiently deep, to keep 

 the most prominent parts of the dressings entirely within 

 their surface. 



The decorations of arcades "may consist of rustics, co- 

 lumns, pilasters, cariatides, persians, or termini, surmount- 

 ed with appropriate entablatures ; and when the piers 

 are of sufficient breadth, niches are introduced. The 

 arch is either surrounded with rustic work, or with an 

 archivolt, sometimes interrupted at the summit with a 

 key stone, -in the form of a console, or marsh, or some 

 other appropriate sculpture. In some instances, the ar- 

 chivolt rises from a platband, or impost, placed on the 

 top of the piers ; in other*, from an entablature, support- 

 ed by columns on either side of the arch. Sometimes 

 the arches are entirely supported by single or coupled 

 column!, without the entablature, as in the temple of 



